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Toxic cyanobacteria induce coupled changes in gut microbiota and co-metabolite of freshwater gastropods
... An ACQUITY UPLC HSS T3 column (1.8 µm, 2.1 × 100 mm) was employed in both positive and negative modes. Water containing 0.1% formic acid was used as mobile phase A. Water and acetonitrile 2/3(v/v) containing 0.1% formic acid was used as mobile phase B. Linear elution conditions and mass spectrometric analysis methods were used [24]. ...
China Xihu Longjing tea is famous for its good flavor and quality. However, information on its related metabolites, except for flavonoids, is largely deficient. Different processing methods for China Xihu Longjing tea fixing—by machines at both the first and second step (A1), first step by machine and second step by hand (A2), first step by hand and second step by machine (A3), and by hand at both the first and second step (A4)—were compared using a UHPLC–QE–MS-based metabolomics approach. Liquid chromatography–mass spectrometry was used to analyze the metabolic profiles of the processed samples. A total of 490 metabolites (3 alkaloids, 3 anthracenes, 15 benzene and substituted derivatives, 2 benzopyrans, 13 coumarins and derivatives, 128 flavonoids, 4 furanoid lignans, 16 glycosides and derivatives, 5 indoles and derivatives, 18 isocoumarins and derivatives, 4 chalcones and dihydrochalcones, 4 naphthopyrans, 3 nucleosides, 78 organic acids and derivatives, 55 organooxygen compounds, 5 phenols, 109 prenol lipids, 3 saccharolipids, 3 steroids and steroid derivatives, and 17 tannins) were identified. The different metabolic profiles were distinguished using PCA and OPLS-DA. There were differences in the types and contents of the metabolites, especially flavonoids, furanoid lignans, glycosides and derivatives, organic acids and derivatives, and organooxygen compounds. There was a positive correlation between flavonoid metabolism and amino acid metabolism. However, there was a negative correlation between flavonoid metabolism and amino acid metabolism, which had the same trend as prenol lipid metabolism and tannins. This study provides new valuable information regarding differences in the metabolite profile of China Xihu Longjing tea processed based on machine fixing and on manual fixing methods.
The environmental impact of increased eutrophication and frequent cyanobacterial blooms on the growth and reproduction of aquatic organisms has become increasingly prominent in recent years. Bellamya aeruginosa is a nutrient-rich aquatic snail consumed by humans, and environmental changes may decrease its meat quality. However, the specific characteristics of muscle metabolism and flavor quality in freshwater snails and their response patterns to bloom-forming cyanobacterial stress have not been reported. Therefore, in this study, alterations in metabolites in the snail muscle after following feeding on toxic Microcystis aeruginosa were investigated using untargeted metabolomics. A total of 1,128 metabolites were identified, and the metabolic pathways of unsaturated fatty acid biosynthesis and purine, glutathione, and glycerophospholipid metabolism in snails fed toxic cyanobacteria differed from those in snails fed Chlorella vulgaris. Quantitative analysis showed increased levels of bitter-free amino acids, such as tyrosine, phenylalanine, and histidine, after consuming toxic cyanobacteria for 42 d, whereas a relative decrease was observed in the levels of umami- and sweet-free amino acids, such as glutamic acid, aspartic acid, serine, threonine, and glicine. The muscles of snails fed toxic cyanobacteria exhibited higher hypoxanthine and hypoxanthine nucleoside and lower adenosine triphosphate, adenine nucleotide, adenine nucleoside diphosphate, and hypoxanthine nucleotide contents than those of snails fed C. vulgaris. Furthermore, increased metabolites, such as stearic acid, palmitic acid, and cytidine diphosphate choline, and decreased metabolites, such as docosapentaenoic acid, docosahexaenoic acid, adrenoic acid, and L-glutamic acid, reflect the harmful effects of toxic cyanobacteria on the nutritional value and flesh quality of B. aeruginosa. This study comprehensively evaluated the effects of cyanobacterial blooms on freshwater gastropods, providing an important theoretical basis for the quality, safety, and sustainable development of snails as food and related processing industries.
Gut microbes play a critical role in helping hosts adapt to external environmental changes and are becoming an important phenotype for evaluating the response of aquatic animals to environmental stresses. However, few studies have reported the role that gut microbes play after the exposure of gastropods to bloom-forming cyanobacteria and toxins. In this study, we investigated the response pa ern and potential role of intestinal flora in freshwater gastropod Bellamya aeruginosa when exposed to toxic and non-toxic strains of Microcystis aeruginosa, respectively. Results showed that the composition of the intestinal flora of the toxin-producing cyanobacteria group (T group) changed significantly over time. The concentration of microcystins (MCs) in hepatopancreas tissue decreased from 2.41 ± 0.12 on day 7 to 1.43 ± 0.10 µg·g −1 dry weight on day 14 in the T group. The abundance of cellulase-producing bacteria (Acinetobacter) was significantly higher in the non-toxic cyanobacteria group (NT group) than that in the T group on day 14, whereas the relative abundance of MC-degrading bacteria (Pseudomonas and Ralstonia) was significantly higher in the T group than that in the NT group on day 14. In addition, the co-occurrence networks in the T group were more complex than that in the NT group at day 7 and day 14. Some genera identified as key nodes, such as Acinetobacter, Pseudomonas, and Ralstonia, showed different pa erns of variation in the co-occurrence network. Network nodes clustered to Acinetobacter increased in the NT group from day 7 to day 14, whereas the interactions between Pseudomonas and Ralstonia and other bacteria almost changed from positive correlations in the D7T group to negative correlations in the D14T group. These results suggested that these bacteria not only have the ability to improve host resistance to toxic cyanobacterial stress by themselves, but they can also further assist host adaptation to environmental stress by regulating the interaction pa erns within the community. This study provides useful information for understanding the role of freshwater gastropod gut flora in response to toxic cyanobacteria and reveals the underlying tolerance mechanisms of B. aeruginosa to toxic cyanobac-teria. Key Contribution: The results of this article mainly show that toxic cyanobacterial stress leads to significant changes in gut microbial composition, community assembly processes, and co-occurrence network relationships in Bellamya aeruginosa, and that these changes are likely to help the host to be er adapt to toxic cyanobacterial stress.
Frequent outbreaks of harmful cyanobacterial blooms and the cyanotoxins they produce not only seriously jeopardize the health of freshwater ecosystems but also directly affect the survival of aquatic organisms. In this study, the dynamic characteristics and response patterns of transcriptomes and gut microbiomes in gastropod Bellamya aeruginosa were investigated to explore the underlying response mechanisms to toxic cyanobacterial exposure. The results showed that toxic cyanobacteria exposure induced overall hepatopancreatic transcriptome changes. A total of 2128 differentially expressed genes were identified at different exposure stages, which were mainly related to antiox-idation, immunity, and metabolism of energy substances. In the early phase (the first 7 days of exposure), the immune system may notably be the primary means of resistance to toxin stress, and it performs apoptosis to kill damaged cells. In the later phase (the last 7 days of exposure), oxidative stress and the degradation activities of exogenous substances play a dominant role, and nutrient substance metabolism provides energy to the body throughout the process. Microbiomic analysis showed that toxic cyanobacteria increased the diversity of gut microbiota, enhanced interactions between gut microbiota, and altered microbiota function. In addition, the changes in gut microbiota were correlated with the expression levels of antioxidant-, immune-, metabolic-related differentially expressed genes. These results provide a comprehensive understanding of gastropods and intestinal microbiota response to toxic cyanobacterial stress. Key Contribution: More than 2100 DEGs were identified by RNA-seq of toxic cyanobacteria-treated snail. Toxic cyanobacteria exposure induced oxidative stress, immune responses, and energy metabolism. Toxic cyanobacteria exposure changed the structure and function of the gut microbiota in snail.
The mud snail Cipangopaludina cathayensis is a widely distributed species in China. Particularly in Guangxi province, mud snail farming contributes significantly to the economic development. However, global warming in recent decades poses a serious threat to global aquaculture production. The rising water temperature is harmful to aquatic animals. The present study explored the effects of high temperature on the intestinal microbiota of C. cathayensis. Snail intestinal samples were collected from the control and high-temperature groups on days 3 and 7 to determine the gut microbiota composition and diversity. Gut bacterial community composition was investigated using high-throughput sequencing of the V3–V4 region of bacterial 16S rRNA genes. Our results suggested that thermal stress altered the gut microbiome structure of C. cathayensis. At the phylum level, Proteobacteria, Bacteroidetes, and Firmicutes were dominant in C. cathayensis gut microbiota. The T2 treatment (32 ± 1 °C, day 7) significantly decreased the relative abundance of Firmicutes, Actinobacteria, and Deinococcus-Thermus. In T2, the abundance of several genera of putatively beneficial bacteria (Pseudomonas, Aeromonas, Rhodobacter, and Bacteroides) decreased, whereas the abundance of Halomonas—a pathogenic bacterial genus—increased. The functional prediction results indicated that T2 treatment inhibited some carbohydrate metabolism pathways and induced certain disease-related pathways (e.g., those related to systemic lupus erythematosus, Vibrio cholerae infection, hypertrophic cardiomyopathy, and shigellosis). Thus, high temperature profoundly affected the community structure and function of C. cathayensis gut microbiota. The results provide insights into the mechanisms associated with response of C. cathayensis intestinal microbiota to global warming.
Freshwater gastropods are widely distributed and play an important role in aquatic ecosystems. Symbiotic microorganisms represented by gut microbes can affect the physiological and biochemical activities of their hosts. However, few studies have investigated the response of the gut microbial community of snails to environmental stress. In this study, the dynamics of the gut microbiota of the gastropod Bellamya aeruginosa were tracked to explore their responses in terms of their composition and function to cyanobacterial bloom. Differences in gut microbial community structures during periods of non-cyanobacterial bloom and cyanobacterial bloom were determined. Results showed that the alpha diversity of the gut microbiota exposed to cyanobacterial bloom was lower than that of the gut microbiota exposed to non-cyanobacterial bloom. The main genera differentiating the two periods were Faecalibacterium, Subdoligranulum, Ralstonia, and Pelomonas. Microcystins (MCs) and water temperature (WT) were the primary factors influencing the gut microbial community of B. aeruginosa; between them, the influence of MCs was greater than that of WT. Fourteen pathways (level 2) were notably different between the two periods. The pathways of carbohydrate metabolism, immune system, environmental adaptation, and xenobiotics biodegradation and metabolism in these differential pathways exhibited a strong linear regression relationship with MCs and WT. Changes in the functions of the gut microbiota may help B. aeruginosa meet its immunity and energy needs during cyanobacterial bloom stress. These results provide key information for understanding the response pattern of freshwater snail intestinal flora to cyanobacterial blooms and reveal the underlying environmental adaptation mechanism of gastropods from the perspective of intestinal flora.
Abstract The interactions between the gut microbiome and metabolome play an important role in human health and diseases. Current studies mainly apply statistical correlation analysis between the gut microbiome and all the identified metabolites to explore their relationship. However, it remains challenging to identify the specific metabolic functions of microbes without in vitro culture experiments for validation. Discriminating the microbial metabolites from others (e.g., host, food, or environment) and exploring their metabolic functions and correlations with microbiome specifically may improve the efficiency and accuracy of biomarker discovery. So far, there have been no such bioinformatics tools available. Herein, we developed MetOrigin, an interactive web server that discriminates metabolites originating from the microbiome, performs the origin‐based metabolic pathway enrichment analysis, and integrates the statistical correlations and biological relationships in the database using Sankey network visualization. MetOrigin not only enables the quick identification of microbial metabolites and their metabolic functions but also facilitates the discovery of specific bacterial species that are closely associated with metabolites statistically and biologically. MetOrigin is freely available at http://metorigin.met-bioinformatics.cn/.
Microcystin-LR (MC-LR) is a hazardous hepatotoxin substance that threaten aquatic animals. Intestinal microbes can interact with and influence the health of their hosts. In this study, the shrimp Litopenaeus vannamei were exposed to 0.1 or 1 µg/L MC-LR for 72 h, and changes in intestinal microbial community and hepatopancreas transcriptome and metabolome were investigated. The results showed that both two doses of MC-LR increased intestinal microbial diversity and caused community composition variation by decreasing the abundances of putatively beneficial bacteria (Alloprevotella, Prevotella 1, Bacteroidales S24–7 group_norank and Lactobacillus). A large number of immune-related genes were differentially expressed in the hepatopancreas, including pattern recognition receptors and antimicrobial molecules; nutrient digestion and detoxification metabolism dysfunction were also induced. Furthermore, MC-LR altered hepatopancreas metabolic phenotypes, especially amino acid metabolism, the citric acid cycle, and linoleic acid and arachidonic acid metabolism. The changes in the intestinal bacteria were correlated with the immune factors and metabolic functions of their host. This study provides evidence for the toxicity of MC-LR on shrimp and identifies several biomarkers associated with the stress response.
The mammalian gut harbors a complex and dynamic microbial ecosystem: the microbiota. While emerging studies support that microbiota regulates brain function with a few molecular cues suggested, the overall biochemical landscape of the “microbiota-gut-brain axis” remains largely unclear. Here we use high-coverage metabolomics to comparatively profile feces, blood sera, and cerebral cortical brain tissues of germ-free C57BL/6 mice and their age-matched conventionally raised counterparts. Results revealed for all three matrices metabolomic signatures owing to microbiota, yielding hundreds of identified metabolites including 533 altered for feces, 231 for sera, and 58 for brain with numerous significantly enriched pathways involving aromatic amino acids and neurotransmitters. Multicompartmental comparative analyses single out microbiota-derived metabolites potentially implicated in interorgan transport and the gut-brain axis, as exemplified by indoxyl sulfate and trimethylamine- N -oxide. Gender-specific characteristics of these landscapes are discussed. Our findings may be valuable for future research probing microbial influences on host metabolism and gut-brain communication.
Molluscan metabolomic analysis is essential for the understanding of the regulatory mechanism of aquatic invertebrate in response to hepatotoxic microcystins (MCs) stress. To understand the system responses of the gastropod to MC exposure, metabolomic alterations caused by two strains (MC-producing and non MC-producing) of Microcystis aeruginosa were characterized indifferent biological matrices (hepatopancreas and muscle) of Bellamya aeruginosa (Gastropoda) using 1H nuclear magnetic resonance (NMR) spectroscopy combined with MCs detections after exposure for 1, 7, and 14 d. Although ELISA analysis showed that no MCs was detected in both tissues after non MC-producing M. aeruginosa exposure, MCs concentrations were increasing in the hepatopancreas (from 1.29±0.48 µg/g to 3.17±0.11 µg/g) and foot muscle (from 0.07±0.02 µg/g to 0.21±0.08 µg/g) after 14-d exposure of MC-producing M. aeruginosa. Meanwhile, we observed that MC induced significant increase in creatine, a variety of amino acids (leucine, isoleucine, valine, threonine, alanine, methionine, glutamate, aspartate, and lysine), carboxylic acids (lactate, acetate, and D-3-hydroxybutyrate), and choline and its derivatives (phosphocholine and glycerophosphocholine) but decreased the energy substance (lipids, glucose, and glycogen) in the hepatopancreas. However, no significant metabolite differences were observed in the muscle between MC-producing and non MC-producing cyanobacteria treated groups. These results suggest that MC exposure may cause hepatic energy expenditure accompanied with various metabolic disorders that involve lipid metabolism, protein catabolism, osmoregulation, glycolysis, glycogenolysis, and tricarboxylic acid (TCA) cycle. Moreover, metabolic perturbation was aggravated as the level of accumulated MCs raised over time in the MC-producing cyanobacteria treatment. These findings indicated that MCs accumulation might lead to oxidative-stress-mediated damage of mitochondria functions.
A dysregulation of cytokine networks has been suggested to be involved in the pathogenesis of unexplained pregnancy loss. Gut microbiota affects host immune response and induces an imbalance in cytokine levels. However, how gut microbial dysbiosis disturbs cellular immune function in miscarriage remains inconclusive. Here we report that IL-2, IL-17A, IL-17F, TNF-α, and IFN-γ are significantly increased in serum of miscarriage patients. Fecal microbiome analyses indicate that microbial diversity and the relative abundances of Prevotella_1, Prevotellaceae_UCG_003 and Selenomonas_1 are significantly reduced in the cases. Correlation analyses indicate that some microbe-associated metabolites are positively associated with changes in levels of Th1/Th17 cytokines in the miscarriage group. Moreover, we identify that imidazolepropionic acid and 1,4-methylimidazoleacetic acid are associated with subsequent recurrent miscarriage. Our study highlights the network among gut microbiota, fecal metabolites and Th1/Th17-mediated immune response in miscarriage patients and explores the potential predictive values of two fecal metabolites for recurrent miscarriages.
The freshwater pulmonate snail Planorbella trivolvis is a common species in various bodies of water but is not native to China. Planorbella trivolvis usually live on diets with high fiber content, such as water grasses, algae and fallen leaves. These snails can attach to the wall of a water tank or to water grass and can be transported overseas to China through the ornamental fish trade. There are few studies investigating the intestinal microbiota of freshwater snails. In this study, using culture-independent molecular analysis, we assessed for the first time the complexity of bacterial communities in the intestines of reared snails. The intestinal microbiota in the snails fed different diets, that is, herbivorous feed (HV) with high cellulose and non-herbivorous feed (NHV) with low cellulose, were analyzed by Illumina sequencing. The results showed that the NHV-based diet significantly increased the body mass, shell diameter and specific growth rate of the snails after 60 days of rearing ( P < 0.05). Histological experiments showed that the fat droplets in the epithelium columnar cells of the intestines of the NHV snails increased, and the cilia on these cells fell off. The sequencing results identified 486 and 195 OTUs in HV and NHV, respectively. Lots of bacteria were not reported previously in snails. The intestinal microbiota diversity index (Shannon, Simpson, Ace and Chao) in the NHV snails was significantly lower than that in the HV snails. The gut microbiota in the HV snails were predominantly Proteobacteria (52.97%) and Bacteroidetes (28.75%), while the gut microbiota in NHV snails were predominantly Proteobacteria (95.23%). At the genus level, Cloacibacterium (24.60%), Pseudomonas (4.47%), OM6ON (6.12%), and Rhodobacter (5.79%) were observed to be abundant in HV snails. However, Aeromonas (85.4%) was determined to be predominant in NHV snails. Functional prediction of the gut microbiome in snails by PICRUSt demonstrated a significant difference between the two groups, and the HV snails exhibited higher lignocellulose enzyme activity than did the NHV snails. This study represents a first step in characterizing the gut microbiota of the freshwater snail. Most of these microbes can process plant biomass and digest cellulose and lignocellulose, and the enzymes of these bacteria may have potential biotechnological applications in a variety of industrial processes.
Raffinose family oligosaccharides (RFOs) are implicated in plant regulatory mechanisms of abiotic stresses tolerance and, despite their antinutritional proprieties in grain legumes, little information is available about the enzymes involved in RFO metabolism in Fabaceae species. In the present study, the systematic survey of legume proteins belonging to five key enzymes involved in the metabolism of RFOs (galactinol synthase, raffinose synthase, stachyose synthase, alpha-galactosidase, and beta-fructofuranosidase) identified 28 coding-genes in Arachis duranensis and 31 in A. ipaënsis. Their phylogenetic relationships, gene structures, protein domains, and chromosome distribution patterns were also determined. Based on the expression profiling of these genes under water deficit treatments, a galactinol synthase candidate gene (AdGolS3) was identified in A. duranensis. Transgenic Arabidopsis plants overexpressing AdGolS3 exhibited increased levels of raffinose and reduced stress symptoms under drought, osmotic, and salt stresses. Metabolite and expression profiling suggested that AdGolS3 overexpression was associated with fewer metabolic perturbations under drought stress, together with better protection against oxidative damage. Overall, this study enabled the identification of a promising GolS candidate gene for metabolic engineering of sugars to improve abiotic stress tolerance in crops, whilst also contributing to the understanding of RFO metabolism in legume species.
Background
Gut microbiota plays important roles in host animal metabolism, homeostasis and environmental adaptation. However, the interplay between the gut microbiome and urochordate ascidian, the most closet relative of vertebrate, remains less explored. In this study, we characterized the gut microbial communities of urochordate ascidian (Halocynthia roretzi) across the changes of season and starvation stress using a comprehensive set of omic approaches including 16S rRNA gene amplicon sequencing, shotgun metagenomics, metabolomic profiling, and transcriptome sequencing.
Results
The 16S rRNA gene amplicon profiling revealed that ascidians harbor indigenous gut microbiota distinctly different to the marine microbial community and significant variations in composition and abundance of gut bacteria, with predominant bacterial orders representing each season. Depressed alpha-diversities of gut microbiota were observed across starvation stress when compared to the communities in aquafarm condition. Synechococcales involving photosynthesis and its related biosynthesis was reduced in abundance while the enrichments of Xanthomonadales and Legionellales may facilitate bile acid biosynthesis during starvation. Metabolomics analysis found that long chain fatty acids, linolenic acid, cyanoamino acid, and pigments derived from gut bacteria were upregulated, suggesting a beneficial contribution of the gut microbiome to the ascidian under starvation stress.
Conclusions
Our findings revealed seasonal variation of ascidian gut microbiota. Defense and energy-associated metabolites derived from gut microbiome may provide an adaptive interplay between gut microbiome and ascidian host that maintains a beneficial metabolic system across season and starvation stress. The diversity-generating metabolisms from both microbiota and host might lead to the co-evolution and environmental adaptation.
Graphical Abstract
Differences in salinity are boundaries that act as barriers for the dispersal of most aquatic organisms. This creates distinctive biota in freshwater and brackish water (mesohaline) environments. To test how saline boundaries influence the diversity and composition of host-associated microbiota, we analyzed the microbiome within the digestive tract of Theodoxus fluviatilis, an organism able to cross the freshwater and mesohaline boundary. Alpha-diversity measures of the microbiome in freshwater and brackish water were not significantly different. However, the composition of the bacterial community within freshwater T. fluviatilis differed significantly compared with mesohaline T. fluviatilis and typical bacteria could be determined for the freshwater and the mesohaline digestive tract microbiome. An artificial increase in salinity surrounding these freshwater snails resulted in a strong change in the bacterial community and typical marine bacteria became more pronounced in the digestive tract microbiome of freshwater T. fluviatilis. However, the composition of the digestive tract microbiome in freshwater snails did not converge to that found within mesohaline snails. Within mesohaline snails, no cardinal change was found after either an increase or decrease in salinity. In all samples, Pseudomonas, Pirellula, Flavobacterium, Limnohabitans, and Acinetobacter were among the most abundant bacteria. These bacterial genera were largely unaffected by changes in environmental conditions. As permanent residents in T. fluviatilis, they may support the digestion of the algal food in the digestive tract. Our results show that freshwater and mesohaline water host-associated microbiomes respond differently to changes in salinity. Therefore, the salinization of coastal freshwater environments due to a rise in sea level can influence the gut microbiome and its functions with currently unknown consequences for, e.g., nutritional physiology of the host.
Microcystins (MCs) classified as hepatotoxic and carcinogenic are the most commonly reported cyanobacterial toxins found in the environment. Microcystis sp. possessing a series of MC synthesis genes (mcyA-mcyJ) are well documented for their excessive abundance, numerous bloom occurrences and MC producing capacity. About 246 variants of MC which exert severe animal and human health hazards through the inhibition of protein phosphatases (PP1 and PP2A) have been characterized. To minimize and prevent MC health consequences, the World Health Organization proposed 1 µg/L MC guidelines for safe drinking water quality. Further the utilization of bacteria that represent a promising biological treatment approach to degrade and remove MC from water bodies without harming the environment has gained global attention. Thus the present review described toxic effects and bacterial degradation of MCs.
Bacteria play key roles in the function and diversity of aquatic systems, but aside from study of specific bloom systems, little is known about the diversity or biogeography of bacteria associated with harmful cyanobacterial blooms (cyanoHABs). CyanoHAB species are known to shape bacterial community composition and to rely on functions provided by the associated bacteria, leading to the hypothesized cyanoHAB interactome, a coevolved community of synergistic and interacting bacteria species, each necessary for the success of the others. Here, we surveyed the microbiome associated with Microcystis aeruginosa during blooms in 12 lakes spanning four continents as an initial test of the hypothesized Microcystis interactome. We predicted that microbiome composition and functional potential would be similar across blooms globally. Our results, as revealed by 16S rRNA sequence similarity, indicate that M. aeruginosa is cosmopolitan in lakes across a 280° longitudinal and 90° latitudinal gradient. The microbiome communities were represented by a wide range of operational taxonomic units and relative abundances. Highly abundant taxa were more related and shared across most sites and did not vary with geographic distance, thus, like Microcystis, revealing no evidence for dispersal limitation. High phylogenetic relatedness, both within and across lakes, indicates that microbiome bacteria with similar functional potential were associated with all blooms. While Microcystis and the microbiome bacteria shared many genes, whole‐community metagenomic analysis revealed a suite of biochemical pathways that could be considered complementary. Our results demonstrate a high degree of similarity across global Microcystis blooms, thereby providing initial support for the hypothesized Microcystis interactome.
Branched-chain amino acid (BCAA; valine, leucine and isoleucine) supplementation is often beneficial to energy expenditure; however, increased circulating levels of BCAA are linked to obesity and diabetes. The mechanisms of this paradox remain unclear. Here we report that, on cold exposure, brown adipose tissue (BAT) actively utilizes BCAA in the mitochondria for thermogenesis and promotes systemic BCAA clearance in mice and humans. In turn, a BAT-specific defect in BCAA catabolism attenuates systemic BCAA clearance, BAT fuel oxidation and thermogenesis, leading to diet-induced obesity and glucose intolerance. Mechanistically, active BCAA catabolism in BAT is mediated by SLC25A44, which transports BCAAs into mitochondria. Our results suggest that BAT serves as a key metabolic filter that controls BCAA clearance via SLC25A44, thereby contributing to the improvement of metabolic health.
Gut bacteria of phytophagous and omnivorous marine invertebrates often possess alginate lyases (ALGs), which are key enzymes for utilizing macroalgae as carbon neutral biomass. We hypothesized that the exclusive feeding of a target alga to marine invertebrates would shift the gut bacterial diversity suitable for degrading the algal components. To test this hypothesis, we reared sea hare (Dolabella auricularia) and sea snail (Batillus cornutus) for two to four weeks with exclusive feeding of a brown alga (Ecklonia cava). Pyrosequencing analysis of the gut bacterial 16S rRNA genes revealed shifts in the gut microbiota after rearing, mainly due to a decrease in the variety of bacterial members. Significant increases in six and four 16S rRNA gene phylotypes were observed in the reared sea hares and sea snails, respectively, and some of them were phylogenetically close to known alginate-degrading bacteria. Clone library analysis of PL7 family ALG genes using newly designed degenerate primer sets detected a total of 50 ALG gene phylotypes based on 90% amino acid identity. The number of ALG gene phylotypes increased in the reared sea hare but decreased in reared sea snail samples, and no phylotype was shared between them. Out of the 50 phylotypes, 15 were detected only after the feeding procedure. Thus, controlled feeding strategy may be valid and useful for the efficient screening of genes suitable for target alga fermentation.
Background/aims:
This study aimed to explore the metabololipidome in mice upon cupping treatment.
Methods:
A nude mouse model mimicking the cupping treatment in humans was established by administrating four cupping sets on the back skin for 15 minutes. UPLC-MS/ MS was performed to determine the PUFA metabolome in mice skin and blood before and after cupping treatment. The significantly changed lipids were administered in macrophages to assess the production of pro-inflammatory cytokines IL-6 and TNF-α by ELISA.
Results:
The anti-inflammatory lipids, e.g. PGE1, 5,6-EET, 14,15-EET, 10S,17S-DiHDoHE, 17R-RvD1, RvD5 and 14S-HDoHE were significantly increased while pro-inflammatory lipids, e.g. 12-HETE and TXB2 were deceased in the skin or plasma post cupping treatment. Cupping treatment reversed the LPS-stimulated IL-6 and TNF-α expression in mouse peritoneal exudates. Moreover, 5,6-EET, PGE1 decreased the level of TNF-α, while 5,6-EET, 5,6-DHET downregulated IL-6 production in macrophages. Importantly, 14,15-EET and 14S-HDoHE inhibited both IL-6 and TNF-α induced by lipopolysaccharide (LPS). 17-RvD1, RvD5 and PGE1 significantly reduced the LPS-initiated TNF-α, while TXB2 and 12-HETE further upregulated the LPS-enhanced IL-6 and TNF-α expression in macrophages.
Conclusion:
Our results reveal the identities of anti-inflammatory versus pro-inflammatory metabolipidome and suggest the potential therapeutic mechanism of cupping treatment.
The contribution of food sources to the freshwater gastropod Bellamya aeruginosa was estimated using stable carbon and nitrogen isotope ratios in three water bodies (two reservoirs and a pond) with different history of cyanobacterial blooms in the eastern part of Zhejiang Province, China. Results of the isotope mixing model showed that filtered food materials (suspended particulate organic matter) contributed most to the diet of B. aeruginosa in both reservoirs with higher levels of chlorophyll a (chl a) in the water column, except during the summer, when a cyanobacteria (Microcystis) bloom occurred in Reservoir Tingxia. In contrast, scraped food materials (benthic detritus) contributed most to the diet of B. aeruginosa in the pond, where low levels of chl a were found in the water column. These results suggest that although filtered food materials were the main food source of B. aeruginosa when the habitat was rich in desirable suspended particles, ingestion of filtered food materials decreased during the cyanobacteria bloom. Feeding experiments were conducted to verify whether snails could avoid ingesting the cyanobacteria. The isotopic ratios in muscle tissue of B. aeruginosa fed by a diet containing only cyanobacteria were similar to those of the no-diet treatment, implying that the snails did not feed, when only cyanobacteria were offered. Moreover, the combination of higher mortality, lower fecal pellet counts, and reduced growth (based on shell height) in the treatment with cyanobacteria indicate that B. aeruginosa stopped feeding when food became undesirable, confirming our field observations that B. aeruginosa avoids feeding on toxic cyanobacteria.
Lake Taihu is the third-largest freshwater lake in China and has been suffering from cyanobacterial blooms for over two decades. The northern part of the lake, Meiliang Bay, is known to be at high risk of dense and sustained Microcystis blooms and toxins. This study aimed to investigate and record the annual and seasonal dynamics of toxic genotype, Microcystis morphospecies succession and microcystin variation. It also aimed to find out the underlying driving factors influencing the dynamic changes. Microcystin (MC) and the Microcystis genotype were quantified using HPLC and quantitative real-time PCR, respectively. Our study, over three consecutive years, showed that the pattern of morphospecies succession was seasonally distinct and annually consistent. During the same period in 2012, 2013 and 2014, the average MC were, on dry weight basis, 733 μg·g(-1), 844 μg·g(-1), 870 μg·g(-1), respectively. The proportion of toxic Microcystis accounted for 41%, 44% and 52%, respectively. Cell bound microcystin was found to correlate with the percentage of toxic Microcystis. Based on historical and current data, we conclude that annual bloom toxicity was relatively stable or possibly increased over the last decade.
Microbial functions in the host physiology are a result of the microbiota-host co-evolution. We show that cold exposure leads to marked shift of the microbiota composition, referred to as cold microbiota. Transplantation of the cold microbiota to germ-free mice is sufficient to increase insulin sensitivity of the host and enable tolerance to cold partly by promoting the white fat browning, leading to increased energy expenditure and fat loss. During prolonged cold, however, the body weight loss is attenuated, caused by adaptive mechanisms maximizing caloric uptake and increasing intestinal, villi, and microvilli lengths. This increased absorptive surface is transferable with the cold microbiota, leading to altered intestinal gene expression promoting tissue remodeling and suppression of apoptosis-the effect diminished by co-transplanting the most cold-downregulated strain Akkermansia muciniphila during the cold microbiota transfer. Our results demonstrate the microbiota as a key factor orchestrating the overall energy homeostasis during increased demand.
Long-term supplementation with branched-chain amino acids (BCAA) is associated with prolonged survival and decreased frequency of development of hepatocellular carcinoma (HCC) in patients with liver cirrhosis. However, the pharmaceutical mechanism underlying this association is still unclear. We investigated whether continuous BCAA supplementation increases survival rate of rats exposed to a fibrogenic agent and influences the iron accumulation, oxidative stress, fibrosis, and gluconeogenesis in the liver. Further, the effects of BCAA on gluconeogenesis in cultured cells were also investigated. A significant improvement in cumulative survival was observed in BCAA-supplemented rats with advanced cirrhosis compared to untreated rats with cirrhosis (P<0.05). The prolonged survival due to BCAA supplementation was associated with reduction of iron contents, reactive oxygen species production and attenuated fibrosis in the liver. In addition, BCAA ameliorated glucose metabolism by forkhead box protein O1 pathway in the liver. BCAA prolongs survival in cirrhotic rats and this was likely the consequences of reduced iron accumulation, oxidative stress and fibrosis and improved glucose metabolism in the liver.
Significance:
The imino acid proline is utilized by different organisms to offset cellular imbalances caused by environmental stress. The wide use in nature of proline as a stress adaptor molecule indicates that proline has a fundamental biological role in stress response. Understanding the mechanisms by which proline enhances abiotic/biotic stress response will facilitate agricultural crop research and improve human health.
Recent advances:
It is now recognized that proline metabolism propels cellular signaling processes that promote cellular apoptosis or survival. Studies have shown that proline metabolism influences signaling pathways by increasing reactive oxygen species (ROS) formation in the mitochondria via the electron transport chain. Enhanced ROS production due to proline metabolism has been implicated in the hypersensitive response in plants, lifespan extension in worms, and apoptosis, tumor suppression, and cell survival in animals.
Critical issues:
The ability of proline to influence disparate cellular outcomes may be governed by ROS levels generated in the mitochondria. Defining the threshold at which proline metabolic enzyme expression switches from inducing survival pathways to cellular apoptosis would provide molecular insights into cellular redox regulation by proline. Are ROS the only mediators of proline metabolic signaling or are other factors involved?
Future directions:
New evidence suggests that proline biosynthesis enzymes interact with redox proteins such as thioredoxin. An important future pursuit will be to identify other interacting partners of proline metabolic enzymes to uncover novel regulatory and signaling networks of cellular stress response.
The composition and activity of the gut microbiota codevelop with the host from birth and is subject to a complex interplay that depends on the host genome, nutrition, and life-style. The gut microbiota is involved in the regulation of multiple host metabolic pathways, giving rise to interactive host-microbiota metabolic, signaling, and immune-inflammatory axes that physiologically connect the gut, liver, muscle, and brain. A deeper understanding of these axes is a prerequisite for optimizing therapeutic strategies to manipulate the gut microbiota to combat disease and improve health.
This study was conducted to investigate ultrastructural alterations and biochemical responses in the hepatopancreas of the freshwater snail Bellamya aeruginosa after exposure to two treatments: toxic cyanobacterium (Microcystis aeruginosa) and toxic cyanobacterial cells mixed with a non-toxic green alga (Scendesmus quadricauda) for a period of 15 days of intoxication, followed by a 15-day detoxification period. The toxic algal suspension induced a very pronounced increase of the activities of acid phosphatases, alkaline phosphatases and glutathione S-transferases (ACP, ALP and GST) in the liver at the later stage of intoxication. During the depuration, enzymatic activity tended to return to the levels close to those in the control. The activity of GST displayed the most pronounced response among different algal suspensions. Severe cytoplasmic vacuolization, condensation and deformation of nucleus, dilation and myeloid-like in mitochondria, disruption of rough endoplasmic reticulum, proliferation of lysosome, telolysosomes and apoptotic body were observed in the tissues. All cellular organelles began recovery after the snails were transferred to the S. quadricauda. The occurrence of a large amount of activated lysosomes and heterolysosomes and augment in activity of detoxification enzyme GST might be an adaptive mechanism to eliminate or lessen cell damage caused by hepatotoxicity to B. aeruginosa.
MC-LR is one of the cyanotoxins produced by fresh water cyanobacteria. Previous studies showed that autophagy played an important role in MC-LR-induced reproduction toxicity. However, information on the toxicological mechanism is limited. In this study, MC-LR could induce autophagy and apoptosis in GCO cells in vitro. In GCO cells that had been exposed to MC-LR, the inhibitor of 3-MA effectively decreased cell viability and damaged cell ultrastructure. Oxidative stress was significantly increased in the 3-MA + MC-LR group, accompanied by significantly increased MDA content and decreased CAT activity and GST, SOD1, GPx, and GR expression levels (P < 0.05). Inflammation was more serious in the 3-MA + MC-LR group than that of MC-LR group, which was evidenced by increasing expression levels of TNFα, IL11, MyD88, TNFR1, TRAF2, JNK, CCL4, and CCL20 (P < 0.05). Interestingly, the significant decrease of Caspase-9, Caspase-7, and Bax expression and significant increase of Bcl-2 and Bcl-2/Bax ratio in 3-MA + MC-LR group compared to MC-LR group, suggesting that extent of apoptosis were reduced. Taken together, these results indicated that MC-LR induced autophagy and apoptosis in GCO cells, however, the inhibition of autophagy decreased the extent of apoptosis, induced more serious oxidative stress and inflammation, which eventually induced cell death. Our findings provided some information for exploring the toxicity of MC-LR, however, the role of autophagy require further study in vivo.
Arachidonic acid (ARA), an n-6 essential fatty acid, plays an important role in human and animal growth and development. The ARA presents in the membrane phospholipids can be released by phospholipase A2. These free arachidonic acid molecules are then used to produce eicosanoids through three different pathways. Previous studies have demonstrated that eicosanoids have a wide range of physiological functions. Although they are generally considered to be pro-inflammatory molecules, recent advances have elucidated they have an effect on innate immunity via regulating the development, and differentiation of innate immune cells and the function of the intestinal epithelial barrier. Here, we review eicosanoids generation in intestine and their role in intestinal innate immunity, focusing on intestinal epithelial barrier, innate immune cell in lamina propria (LP) and their crosstalk.
Microcystis aeruginosa bloom in aquatic ecosystems is a worldwide problem that threaten aquatic animals. Fish are an unavoidable link between toxic cyanobacteria and human health. A stable microbiota is an important barrier for fish in defence against pathogen invasion. Therefore, in this study, we investigated the microbiota characteristics in different parts of the gastrointestinal tract and faeces of Lateolabrax maculatus that were cultured in a pond with a naturally occurring M. aeruginosa bloom. Compared with those of the healthy fish, the cyanobacterial bloom decreased the serum immune indexes of the diseased fish, such as the immunoglobulin M content and lysozyme activity. Microbiome analysis showed that the M. aeruginosa bloom did not change the microbial richness and diversity of the diseased fish but significantly altered the community composition. Specifically, M. aeruginosa bloom increased the abundance of Proteobacteria but decreased the abundance of Firmicutes; some genera of pathogenic bacteria (Acinetobacter, Mycobacterium and Staphylococcus) were abundant, while some beneficial bacteria (Lactobacillus and Lactococcus) were reduced. Our results reveal that M. aeruginosa bloom significantly impair the immunity and gastrointestinal microbiota composition of L. maculatus and that microbiota variation may be a factor causing almost all fishes exhibit unhealthy or diseased characteristics. These results will be helpful for the utilization of microbiome characteristics to facilitate healthy fish farming in cyanobacterial bloom environments.
Gut microbiota of wildlife are usually exposed to and involved in degrading environmental pollutants, yet their biodegrading capacity remains largely unexplored. Here, we analyzed gut microbial profiles of a marine benthic polychaete, Nereis succinea, and elaborated the capacity of gut microbiota in degrading various organic pollutants, including polycyclic aromatic hydrocarbons, pesticides, phenols, and synthetic musks. High-throughput sequencing analysis revealed that the structures of microbial communities, including bacteria, fungi, and archaea, varied along the gut, manifesting distinct structural features in the fore-, mid-, and hindgut regions. Community-level physiological profiles and the capacity of gut microbiota in degrading the pollutants showed profound gut region and oxygen dependent features. In general, anaerobes were more active in degrading the pollutants, and those in the midgut presented the maximum degrading potential. Degradation capability of the gut microbiota was further quantitatively validated in an in vitro culture system using chlorpyrifos and malathion as representative compounds. Our results demonstrated a potential impact of gut microbiota in wildlife on the fate of organic pollutants in the ecosystem, which calls for further research on the influences of gut microbiota on biotransformation and bioaccumulation of xenobiotics in organisms.
Eicosanoids mediate both cellular and humoral immune responses in insects. Epoxyeicosatrienoic acids (EETs) are a group of eicosanoids containing epoxide formed by epoxygenase (EPX) activity of cytochrome P450 (CYP). Although EETs have been considered to mediate immune responses in some insects, their synthetic machinery was little understood in insects. This study monitored EETs in a lepidopteran insect, Spodoptera exigua, immunized with bacteria and found all four EETs (5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET) from larval fat body at 247–1,736 pg/g levels. Then to predict EPXs, 140 CYPs were collected from S. exigua transcriptomes and compared with human EPXs. Four CYPs (SeEPX1-SeEPX4) sharing homologies with human EPXs were chosen and assessed in subsequent expression and functional analyses. All four EPXs were expressed in all development stages. In larval stage, all four EPXs were expressed in immune-associated tissues such as fat body and hemocytes. Furthermore, their expression levels were highly enhanced by bacterial challenge in different tissues. RNA interference (RNAi) using gene-specific double stranded RNA injection suppressed their expression levels by more than 55%. RNAi treatments interfered with hemocyte-spreading behavior and nodule formation upon bacterial challenge except RNAi treatment against SeEPX2. All four EETs stimulated cellular immune response measured by nodule formation in S. exigua. The suppressed immune responses by the RNAi treatments against three SeEPXs were rescued by the addition of 8,9-EET. However, other three EETs gave their specific rescue effect depending on SeEPX types under RNAi. In humoral immune response, all four RNAi treatments suppressed expression of antimicrobial peptide genes. This study reports the presence of all four EETs in larval fat body of S. exigua and suggests that four SeEPXs are associated with immune responses mediated by EETs.
This study aimed to evaluate the influence of dietary pure linseed oil or sesame oil or a mixture on innate immune competence and eicosanoid metabolism in common carp (Cyprinus carpio). Carp of 100.4 ± 4.7 g were fed to satiation twice daily for 6 weeks with four diets prepared from three lipid sources (CLO; LO; SO; SLO). On day 42, plasma was sampled for immune parameter analyses, and kidney and liver tissues were dissected for gene expression analysis. On day 45, HKL and PBMCs from remaining fish were isolated and exposed to E. coli LPS at a dose of 10 μg/mL for 24 h. Results show that the SLO diet enhanced feed utilisation (P = 0.01), while no negative effects on growth or survival were observed in plant oil-fed fish compared to those fed a fish-oil based diet. Plant oil diets did not alter lysozyme and peroxidase activities or gene expression levels. Moreover, the diets did not affect the expression levels of some genes involved in eicosanoid metabolism processes (pla, pge2, lox5). Lys expression in HKL in vitro following exposure to LPS was up-regulated in LO-fed fish, while expression levels of pge2 were higher in SLO fish than in other groups (P < 0.05). The highest value for peroxidase activity in HKL exposed to LPS was found in the SLO-fed group (P < 0.05). In conclusion, our results indicate that dietary plant oils did not induce any negative effects on fish growth, survival, and immune competence status. Moreover, a dietary combination of SO and LO improved the feed utilisation efficiency and seemed more effective in inducing a better immunomodulatory response to LPS through a more active eicosanoid metabolism process.
Mounting an immune response is an energy-consuming process. Activating immune functions requires the synthesis of many new molecules and the undertaking of numerous cellular tasks and it must happen rapidly. Therefore, immune cells undergo a metabolic switch, which enables the rapid production of ATP and new biomolecules. Such metabolism is very nutrient-demanding, especially of glucose and glutamine, and thus the immune response is associated with a systemic metabolic switch, redirecting nutrient flow towards immunity and away from storage and consumption by non-immune processes. The immune system during its activation becomes privileged in terms of using organismal resources and the activated immune cells usurp nutrients by producing signals which reduce the metabolism of non-immune tissues. The insect fat body plays a dual role in which it is both a metabolic organ, storing energy and providing energy to the rest of the organism, but also an organ important for humoral immunity. Therefore, the internal switch from anabolism to the production of antimicrobial peptides occurs in the fat body during infection. The mechanisms regulating metabolism during the immune response ensure adequate energy for an effective response (resistance) but they must be properly regulated because energy is not unlimited and the energy needs of the immune system thus interfere with the needs of other physiological traits. If not properly regulated, the immune response may in the end decrease fitness via decreasing disease tolerance.
Microalgae biomass is used in aquaculture as feed, growth enhancers and immunostimulants. Chlorella vulgaris is an important species with a good biomolecular composition. Commercially, it is one of the most commonly used microalga in aquaculture. Several studies confirmed its ability to improve nutrition, immunity, aquatic bioremediation, amelioration of stress, disease resistance of fish and inhibits bacterial quorum sensing when used appropriately. Despite claims of its benefits, C. vulgaris is reported to have unfavourable effects when incorporated in diets at higher inclusion levels. In addition, its rigid cell wall might restrict the access of digestive enzymes to the intracellular components for proper digestion and assimilation. Thus, this review discusses the role of C. vulgaris and its importance in aquaculture with emphasis on its environmental requirements, morphology, pigments, digestibility, dynamics on growth performance, antibacterial activity, bacterial quorum sensing, immunomodulatory effect, anti‐stress effect, gut microbiome, aquatic bioremediation and its safety as food or feed.
The emulsification disease of swimming crab Portunus trituberculatus is mainly caused by Vibrio alginolyticus. Gut microbiota is involved in the immunity and diseases of crustaceans. In this study, we integrated 16S rRNA gene sequencing and ¹H nuclear magnetic resonance metabolomics techniques to determine the effects of V. alginolyticus infection on bacterial composition and metabolic phenotype in the gut of P. trituberculatus. The results showed that V. alginolyticus infection induced marked changes in the gut bacterial composition of P. trituberculatus, which seems to drive the gut bacterial community into a kind of diseased status. The sums of the relative abundance of these indicator bacteria such as Vibrionaceae and Pseudoalteromonadaceae could be used to predict the increased risk of emulsification disease occurrence in swimming crab. V. alginolyticus infection also caused marked changes in the gut metabolic phenotype of P. trituberculatus, highlighted by the significantly changed levels of maltose, glucose, AMP, and amino acids. Importantly, the gut indicator bacteria showed comprehensive correlations with these significantly changed gut metabolites, which revealing the contributions of gut bacteria in pathogenesis of gut metabolic disorders of swimming crab after V. alginolyticus infection. Overall, this study provides solid evidence that gut bacteria are involved in the occurrence and development of crab vibriosis, which could be great important for gaining new insights into the pathogenesis mechanisms of emulsification disease and developing novel strategies for emulsification disease prevention of swimming crab.
Cyanobacteria can form dense and sometimes toxic blooms in freshwater and marine environments, which threaten ecosystem functioning and degrade water quality for recreation, drinking water, fisheries and human health. Here, we review evidence indicating that cyanobacterial blooms are increasing in frequency, magnitude and duration globally. We highlight species traits and environmental conditions that enable cyanobacteria to thrive and explain why eutrophication and climate change catalyse the global expansion of cyanobacterial blooms. Finally, we discuss management strategies, including nutrient load reductions, changes in hydrodynamics and chemical and biological controls, that can help to prevent or mitigate the proliferation of cyanobacterial blooms.
Due to their prebiotic potential indigestible oligosaccharides became a major focus of research interest. In this study the growth of selected probiotic strains including lactobacilli, bifidobacteria, Lactococcus lactis, Streptococcus salivarius ssp. thermophilus, Pediococcus ssp. and Enterococcus faecium with the, raffinose family oligosaccharides (RFOs) raffinose, stachyose and verbascose and galactomannan from guar bean Cyamopsis tetragonoloba (total guar carbohydrates, oligosaccharides (dp 2–4) and polysaccharides (dp > 5), obtained by size exclusion chromatography) were tested by means of turbidity measurements. RFOs were used by 75% of all strains, with some delay for the trisaccharide raffinose and the tetrasaccharide stachyose and a limited fermentation of the pentasaccharide verbascose. L. reuteri, P. pentosaceus and B. lactis HNO19™ were able to ferment not only raffinose and stachyose but also verbascose. Guar oligosaccharides were fermented by 15 out of 20 strains; P. acidilactici, L. acidophilus, L. rhamnosus GG and B. animalis ssp. lactis BB12 metabolized them comparably well as glucose or galactose. Isolated guar polysaccharides were not fermented whereas total guar carbohydrates were fermented by 7 strains, apparently caused by the oligosaccharide content. The findings of this study may be important for functional food products especially for indigestible oligosaccharides which may cause adverse effects in the gut when not cleaved.
Bacterial communities associated to eukaryotes play important roles in the physiology, development, and health of their hosts. Here, we examine the intestinal microbiota in tadpoles and aquatic invertebrates (insects and gastropods) to better understand the degree of specialization in the tadpole microbiotas. Samples were collected at the same time in one pond, and the V4 region of the bacterial 16S rRNA gene was sequenced with Illumina amplicon sequencing. We found that bacterial richness and diversity were highest in two studied snail individuals, intermediate in tadpoles, and lowest in the four groups of aquatic insects. All groups had substantial numbers of exclusive bacterial operational taxonomic units (OTUs) in their guts, but also shared a high proportion of OTUs, probably corresponding to transient environmental bacteria. Significant differences were found for all pairwise comparisons of tadpoles and snails with the major groups of insects, but not among insect groups or between snails and tadpoles. The similarity between tadpoles and snails may be related to similar feeding mode as both snails and tadpoles scratch biofilms and algae from surfaces; however, this requires confirmation due to low sample sizes. Overall, the gut microbiota differences found among syntopic aquatic animals are likely shaped by both food preferences and host identity.
Low dose but long-term exposure of microcystin-LR (MC-LR) could induce human hepatitis and promote liver cancer according to epidemiological investigation results, but the exact mechanism has not been completely elucidated. In the present study, a chronic toxicity test of MC-LR exposure on HepG2 cells at 0.1-30 nM for 83 d was conducted under laboratory conditions. The western blot assay result revealed that MC-LR entered HepG2 cells, even at the concentration of 0.1 nM, after 83 d of exposure, but no cytotoxicity was observed in the HepG2 cells, as determined by the CCK-8 and LDH tests. However, the results of the DCF fluorescence assay showed that the intracellular ROS level in the 30 nM MC-LR-treated cells was significantly higher than that of the control cells, and 5 and 10 nM of MC-LR exposure totally increased the activity of SOD in HepG2 cells. These results indicate that MC-LR exposure at low concentration also induced excessive ROS in HepG2 cells. Additionally, long-term exposure of MC-LR at low concentration remarkably promoted the expression of NF-κB p65, COX-2, iNOS, TNF-α, IL-1β, and IL-6 in the cells, suggesting that long-term MC-LR exposure at low concentration can induce inflammatory reaction to HepG2 cells, which might account for MC-induced human hepatitis. Thus, we hypothesized that the pathogenesis of human hepatitis and hepatocarcinoma caused by MCs might be closely associated with oxidative stress and inflammation.
Cyanotoxins are secondary metabolites produced by cyanobacteria. Cyclic peptides, microcystins and nodularin commonly detected in water reservoirs of different parts of the world may induce various detrimental effects in a wide range of organisms from bacteria to humans. This paper presents the current state of knowledge on the effects of microcystins and nodularin on aquatic invertebrates: zooplankton, decapods and mollusks. Accumulation of microcystins and nodularin in these organisms and possible transfer of the cyanotoxins through the food web and possible threat to humans as consumers are also discussed.
The single and combined effects of toxic cyanobacteria Microcystis aeruginosa and hypoxia on the energy budget of triangle sail mussel Hyriopsis cumingii were determined in terms of scope for growth (SfG). Mussels were exposed to different combinations of toxic M. aeruginosa (0%, 50%, and 100% of total dietary dry weight) and dissolved oxygen concentrations (1, 3, and 6.0 mg O2l-1) with a 3×3 factorial design for 14 days, followed by a recovery period with normal conditions for 7 days. Microcystin contents in mussel tissues increased with the increase in the exposed M. aeruginosa concentration at each sampling time. Adverse physiological responses of H. cumingii under toxic M. aeruginosa and hypoxic exposure were found in terms of clearance rate, absorption efficiency, respiration rate, excretion rate, and SfG. Results emphasized the importance of combined effects of hypoxia and toxic cyanobacteria on H. cumingii bioenergetic parameters, highlighted the interactive effects of toxic algae and hypoxia, and implied that the two stressors affected H. cumingii during the exposure period and showed carryover effects later. Thus, if H. cumingii is used as a bioremediation tool to eliminate M. aeruginosa, the waters should be oxygenated.
Mounting an immune response requires substantial energy. Ecological immunology theory predicts allocation trade‐offs between reproductive effort and immune responses under conditions of energy limitation. Little is known about the impact of capital breeding strategies on energy allocation to immune function in mammals.
Northern elephant seals ( NES ) forage in the marine environment, breed in dense terrestrial colonies and exhibit high rates of energy expenditure for lactation while fasting. Body reserves strongly influence reproductive effort and lactation requires elevation of plasma cortisol for energy mobilization.
We characterized immune response by measuring a suite of immune markers including cytokines, an acute phase protein, and immunoglobulins early and late in breeding and moult haul‐outs in 197 samples from 129 female NES . We explored potential impacts of breeding, body condition and plasma cortisol on immune function.
Immune responses were greater and more varied during breeding. Adiposity had positive associations with innate immune responses across all life‐history stages. Body mass had positive associations with both adaptive and innate immune responses early in fasts. Females with lower fat reserves showed reduced innate immune responses at the end of lactation. Immunoglobulin E , a marker of immune response to parasitic infection, exhibited a significant negative association with cortisol across all life‐history stages.
These data suggest that breeding carries an immune cost and provide evidence for allocation trade‐offs between immune function and breeding effort. These trade‐offs may reflect a compromise between immune costs inherent in colonial breeding and energetic limitations that arise in use of capital breeding strategies. Variation in evidence for immunosuppressive effects of cortisol suggests that decoupling of these effects may be limited to specific aspects of the immune response during terrestrial fasting. Immune responses that are required for survival may be modulated relative to the energetic demands required for successful reproduction.
Cyanobacteria blooms caused by eutrophication lead to serious impacts on aquatic ecosystems and human health. Biomanipulation, using aquatic animals to reduce the algal population, is one of most promising strategies for controlling cyanobacteria blooms and improving water quality. In preliminary experiments in aquaculture ponds, the stocking of the pulmonata snail Lymnaea spp. led to reduced cyanobacterial cell density in highly trophic water. In the present study, the inhibitory effects of Lymnaea spp. against the growth of natural mixed cyanobacteria or of Microcystis aeruginosa were examined. The results indicated that the growth of mixed natural cyanobacteria with an initial cell density of 4 × 105 cell/mL was remarkably inhibited by the presence of Lymnaea spp. with a density of five individuals per liter. The growths of M. aeruginosa with various initial cell densities of 1.76 × 106, 4.38 × 106, 14.25 × 106, 25.55 × 106, and 69.1 × 106 cells/mL were inhibited by introducing 15 or even fewer individuals into one liter of algal culture. Lymnaea spp. adapted and survived in the water containing M. aeruginosa with cell densities up to 69.1 × 106 cell/mL. Moreover, the reduction in cyanobacteria density by Lymnaea sp. was dependent on filter feeding and associated microorganisms. Therefore, Lymnaea spp. possess the potential to be used as a biomanipulation species.
Bellamya aeruginosa (Reeve) is a predominant benthic macroinvertebrate in many shallow lakes along the middle and lower basins of the Yangtze River, and there is little published information on its production in China by far. This paper dealed with the population dynamics and production of B. aeruginosa, a subtropical, shallow, eutrophic lake located near the middle reaches of the Yangtze River. B. aeruginosa was sampled monthly at the eleven stations in Lake Donghu from June 1998 to May 1999. The results showed that the annual average density and biomass were 92.2ind./m 2 and 142.83g/m 2 , respectively, and the density and biomass
On the basis of a comparative study of 178 strains of cyanobacteria, representative of this group of prokaryotes, revised definitions of many genera are proposed. Revisions are designed to permit the generic identification of cultures, often difficult through use of the field-based system of phycological classification. The differential characters proposed are both constant and readily determinable in cultured material. The 22 genera recognized are placed in five sections, each distinguished by a particular pattern of structure and development. Generic descriptions are accompanied by strain histories, brief accounts of strain properties, and illustrations; one or more reference strains are proposed for each genus. The collection on which this analysis was based has been deposited in the American Type Culture Collection, where strains will be listed under the generic designations proposed here.
Omega-6 (n-6) and omega-3 (n-3) polyunsaturated fatty acids (PUFA) are precursors of potent lipid mediators, termed eicosanoids, which play an important role in the regulation of inflammation. Eicosanoids derived from n-6 PUFAs (e.g., arachidonic acid) have proinflammatory and immunoactive functions, whereas eicosanoids derived from n-3 PUFAs [e.g., eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] have anti-inflammatory properties, traditionally attributed to their ability to inhibit the formation of n-6 PUFA-derived eicosanoids. While the typical Western diet has a much greater ratio of n-6 PUFAs compared with n-3 PUFAs, research has shown that by increasing the ratio of n-3 to n-6 fatty acids in the diet, and consequently favoring the production of EPA in the body, or by increasing the dietary intake of EPA and DHA through consumption of fatty fish or fish-oil supplements, reductions may be achieved in the incidence of many chronic diseases that involve inflammatory processes; most notably, these include cardiovascular diseases, inflammatory bowel disease (IBD), cancer, and rheumatoid arthritis, but psychiatric and neurodegenerative illnesses are other examples.
This study aimed to develop original laboratory culture and sediment toxicity testing protocols for the freshwater gastropod Bellamya aeruginosa (Reeve), a new potential species for sediment toxicity testing. B. aeruginosa was successfully cultured with an effective culture system under proposed laboratory conditions. Optimal ad libitum feeding levels for larvae, juveniles, and adults were 2.0, 6.0, and 16.0 mg fish food/(snail x day), respectively. Mean survival rates of juveniles were higher than 90%. The snails could be sexed at 9 weeks of age, and their generation time is approximately 4 months. Reproduction continued all year around; the mean fecundity was 0.55 newborn/(female x day). The utility of this species for bioassays was evaluated in both 10-day and 28-day case studies with artificial sediments. The 10-day LC50 of Cu for larvae was 480 gg/g dry weight (dw), and the lowest observed effects concentration of Cu for survival and growth of larvae was 195 microg/g dw. Survival and growth are reliable indicators of acute toxicity. Larvae accumulated more Cu than adults. B. aeruginosa exhibited a higher sensitivity to Cu exposure than standard test species (Hyalella azteca and Chironomus tentans). The 28-day test of sediment toxicity with adults showed that fecundity was a robust endpoint indicator of reproductive toxicity, and the biochemical endpoints of superoxide dismutase, catalase, and glutathione could be used as sensitive biomarkers for Cu-induced oxidative damage. B. aeruginosa can be therefore recommended as a candidate for the standardization of the freshwater sediment toxicity test protocol.