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Catabolic pathway of tyrosine metabolism and representative genetic loci. Predicted enzymes encoded by the respective genetic loci in V. cholerae are as follows: VC1344, 4-hydroxyphenylpyruvate dioxygenase; VC1345, homogentisate 1,2-dioxygenase; VC1347, maleylacetoacetate isomerase; VC1346, fumarylacetoacetase. The proposed pathway is based in part on the pathway described for Streptomyces avermitilis (5).
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We identified the mutated gene locus in a pigment-overproducing Vibrio cholerae mutant of strain A1552. The deduced gene product is suggested to be an oxidoreductase based on partial homology to putative
homogentisate 1,2-dioxygenase in Pseudomonas aeruginosa and Mesorhizobium loti, and we propose that the gene VC1345 in the V. cholerae genome be d...
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Citations
... To date, many studies have reported that laccase is related to the pathogenicity of many plant pathogens. In Cryphonectria parasitica, laccase was related to its pathogenicity and the synthesis of melanin [30,31]. ...
Colletotrichum gloeosporioides is one of the most serious diseases that causes damage to mangoes. Laccase, a copper-containing polyphenol oxidase, has been reported in many species with different functions and activities, and fungal laccase could be closely related to mycelial growth, melanin and appressorium formation, pathogenicity, and so on. Therefore, what is the relationship between laccase and pathogenicity? Do laccase genes have different functions? In this experiment, the knockout mutant and complementary strain of Cglac13 were obtained through polyethylene glycol (PEG)-mediated protoplast transformation, which then determined the related phenotypes. The results showed that the knockout of Cglac13 significantly increased the germ tube formation, and the formation rates of appressoria significantly decreased, delaying the mycelial growth and lignin degradation and, ultimately, leading to a significant reduction in the pathogenicity in mango fruit. Furthermore, we observed that Cglac13 was involved in regulating the formation of germ tubes and appressoria, mycelial growth, lignin degradation, and pathogenicity of C. gloeosporioides. This study is the first to report that the function of laccase is related to the formation of germ tubes, and this provides new insights into the pathogenesis of laccase in C. gloeosporioides.
... Another critical regulatory protein at the mucosal surface is the quorum sensing master regulator HapR, which is repressed upon mucosal penetration (Liu et al. 2008). HapR has been shown to activate the T6SS and likely plays a role in in vivo T6SS expression for O1 El Tor strains at the mucosal surface and potentially during the mucosal escape response (Nielsen et al. 2006;Tsou et al. 2009;Ishikawa et al. 2009; Shao and Bassler 2014) ( Fig. 3.3). These results support a model in which the presence of mucus components triggers the T6SS to compete with the resident host gut microbiome residing upon the mucus layer of the gastrointestinal tract. ...
... Both V. cholerae and V. vulnificus can use DMSP as an osmolyte. In environments with high salinity, V. cholerae increases the production of the pigment melanin that provides resistance to UV radiation (Coyne and al-Harthi 1992;Valeru et al. 2009). ...
The Vibrionaceae is a highly diverse family of aquatic bacteria. Some members of this ubiquitous group can cause a variety of diseases in humans ranging from cholera caused by Vibrio cholerae, severe septicemia caused by Vibrio vulnificus, to acute gastroenteritis by Vibrio parahaemolyticus. Planet Earth is experiencing unprecedented changes of planetary scale associated with climate change. These environmental perturbations paired with overpopulation and pollution are increasing the distribution of pathogenic Vibrios and exacerbating the risk of causing infections. In this chapter, we discuss various aspects of Vibrio infections within the context of the twenty-first century with a major emphasis on the aforementioned pathogenic species. Overall, we believe that the twenty-first century is posed to be both one full of challenges due to the rise of these pathogens, and also a catalyst for innovative and groundbreaking discoveries.KeywordsVibrio infectionsClimate changeCholeraGlobal warming
Vibrio parahaemolyticus
Vibrio vulnificus
... Another critical regulatory protein at the mucosal surface is the quorum sensing master regulator HapR, which is repressed upon mucosal penetration (Liu et al. 2008). HapR has been shown to activate the T6SS and likely plays a role in in vivo T6SS expression for O1 El Tor strains at the mucosal surface and potentially during the mucosal escape response (Nielsen et al. 2006;Tsou et al. 2009;Ishikawa et al. 2009; Shao and Bassler 2014) ( Fig. 3.3). These results support a model in which the presence of mucus components triggers the T6SS to compete with the resident host gut microbiome residing upon the mucus layer of the gastrointestinal tract. ...
... Both V. cholerae and V. vulnificus can use DMSP as an osmolyte. In environments with high salinity, V. cholerae increases the production of the pigment melanin that provides resistance to UV radiation (Coyne and al-Harthi 1992;Valeru et al. 2009). ...
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Vibrio cholerae
Carbon utilizationNutrient uptakeHost colonizationHost–pathogen interaction
... To protect against oxidative stress, melanin from Burkholderia cenocepacia neutralizes reactive oxygen species (ROS) generated by the oxidative burst in host cells [20]. Melanin from V. cholerae increases ROS production, toxin and pilus expression, as well as enhances host colonization and protection from amoeba predation [4,21]. During chronic infections, Pseudomonas aeruginosa increases melanin production to resist oxidative stress [14]. ...
Pigments are chromophores naturally synthesized by animals, plants, and microorganisms, as well as produced synthetically for a wide variety of industries such as food, pharmaceuticals, and textiles. Bacteria produce various pigments including melanin, pyocyanin, bacteriochlorophyll, violacein, prodigiosin, and carotenoids that exert diverse biological activities as antioxidants and demonstrate anti-inflammatory, anti-cancer, and antimicrobial properties. Nontuberculous mycobacteria (NTM) include over 200 environmental and acid-fast species; some of which can cause opportunistic disease in humans. Early in the study of mycobacteriology, the vast majority of mycobacteria were not known to synthesize pigments, particularly NTM isolates of clinical significance such as the Mycobacterium avium complex (MAC) species. This paper reviews the overall understanding of microbial pigments, their applications, as well as highlights what is currently known about pigments produced by NTM, the circumstances that trigger their production, and their potential roles in NTM survival and virulence.
... Pyomelanin enhances bacterial surface attachment, biofilm formation, extracellular electron transfer, resistance to heavy metals, iron reduction/acquisition, and induces virulence factor expression, which increase the adaptive response to environmental stress. (9,10) The pyomelanin production results from a defect in the catabolism pathway. Pseudomonas putida metabolises Phe and Tyr through a peripheral pathway, regulated by the σ 54 -dependent transcriptional activator PhhR, involving hydroxylation of Phe to Tyr by PhhAB, conversion of Tyr into 4-hydroxyphenylpyruvate by TyrB, and formation of HGA by Hpd as the central intermediate. ...
... (12,13) The accumulated HGA is then secreted from the cell via the HatABCDE ABC transporter, where it auto-oxidises, and self-polymerises to form pyomelanin. (14) The production of this pigment is quite common in species such as Legionella, Vibrio cholerae and Pseudomonas sp. (9,10,11,12,13) However, pyomelanin production is a rare phenotype in A. baumannii, (15) and the genes involved with its biosynthesis have not yet been unveiled. ...
BACKGROUND
Acinetobacter baumannii outbreaks have been associated with pandemic International Clones (ICs), but the virulence factors involved with their pathogenicity are sparsely understood. Pigment production has been linked with bacterial pathogenicity, however, this phenotype is rarely observed in A. baumannii.
OBJECTIVES
This study aimed to characterise the reddish-brown pigment produced by A. baumannii strains, and to determine its biosynthetic pathway by genomic approaches.
METHODS
Pigment characterisation and antimicrobial susceptibility were conducted by phenotypic tests. The clonal relationship was obtained by pulsed field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). The genome of an A. baumannii was obtained for characterisation of genes involved with pigment production.
FINDINGS
The pyomelanin was the pigment produced by A. baumannii. Strains were extensively drug resistant and belonged to the IC-5/ST79. The pyomelanin biosynthetic pathway was determined and presented a particular architecture concerning the peripheral (tyrB, phhB and hpd) and central (hmgB, hmgC and hmgR) metabolic pathway genes. The identification of a distant HmgA homologue, probably without dioxygenase activity, could explain pyomelanin production. Virulence determinants involved with adherence (csuA/BABCDE and a T5bSS-carrying genomic island), and iron uptake (basABCDEFGHIJ, bauABCDEF and barAB) were characterised.
MAIN CONCLUSION
There is a biosynthetic pathway compatible with the pyomelanin production observed in persistent A. baumannii IC-5 strains.
... The phyllosphere is a harsh environment for microbial life: epiphytes are exposed to fluctuating environmental stresses, like solar radiation, low water availability and hyperosmotic stress, and nutrients are limited by the plant metabolism (Lindow and Brandl, 2003;Valeru et al., 2009). Therefore, phyllospheric microbes have developed specific epiphytic-fitness traits, including their oligotrophic metabolism, several UV-protecting mechanisms (like pigmentation, high capacity of DNA repair and detoxification of reactive oxygen species), the preferential colonization of UV radiation (UVR)-protected sites of the plant, and the production of biosurfactants to move across the surfaces and of extracellular polymeric substances to protect against desiccation (Delmotte et al., 2009;Gunasekera and Sundin, 2006;Jacobs et al., 2005;Schreiber et al., 2005;Yu et al., 1999). ...
... Microbial populations in the phyllosphere can affect plant health positively or negatively. In fact, indigenous microbiota might affect the outcome of plant-pathogen interactions in the phyllosphere (Beattie and Lindow, 1995;Innerebner et al., 2011;Valeru et al., 2009). Foliar bacterial pathogens cause https://doi.org/10.1016/j.rhisph.2020.100207 ...
... factors (Coyne and al-Harthi, 1992;Noorian et al., 2017;Valeru et al., 2009). Besides, for some Pseudomonas strains isolated from decomposed dairy meals, it has been demonstrated that the pigment production varied with the growth conditions, and it was higher under glucose-rich conditions, like on potato dextrose agar (Andreani et al., 2015;Reichler et al., 2019). ...
Bacteria of the Pseudomonas genus have been widely studied due to their antagonistic potential against a diverse group of fungal and bacterial phytopathogens, and their competence to colonize different plant tissues. We have isolated a rhizospheric pseudomonad that produced a black pigment, which is not a widespread trait within this genus. We confirmed that the isolate belonged to the P. putida complex through a MLSA analysis. We observed that the pigment synthesis was enhanced under high C:N ratios (25:1) and it was dependent of the carbon source, being maximized when we added glucose to M9. Besides, the supplementation of M9 with tryptophan inhibited the pigment production under C:N ratios of 4:1, and the addition of kojic acid reduced notably the pigment under favorable conditions. Ps. black presented several traits associated with plant-growth promoting potential with classical in vitro assays. Through a Tn5 mutagenesis approach, we found 2 representative clones, PB1 and PB5, that were consistently unable to produce the pigment under several growth conditions and were not altered in their in vitro probiotic traits. When comparing with PB1 and PB5 performances, we observed that the pigment gives Ps. black a higher tolerance to oxidative stress and UV radiation exposure. When confronting Ps. black with different bacterial phytopathogens, we demonstrated that Ps. black could inhibit the growth of Xanthomonas vesicatoria Bv5-4a, Pseudomonas syringae pv. tomato DC3000, P. syringae pv. syringae B728a, P. savastanoi pv. glycinea B076 and Clavibacter michiganensis subsp. michiganensis Cm9. Except for Psg B076, this antagonism was lost for PB1 and PB5 and when performing the test for Ps. black with tryptophan supplementation. Thus, we suggest that the pigment should be involved in the bacterial antagonisms, and that Ps black contains more than one antibacterial mechanism.
... Melanin can increase microbial virulence through two mechanisms: it reduces the susceptibility of the pathogen to host defense mechanisms and affects the host immune response to infection (Nosanchuk and Casadevall 2006). In melanogenic V. cholerae, pigment production increases cholera toxin and pilus expression, and enhances host colonization (Valeru et al. 2009). Due to its free radical scavenging potential, melanin can diminish host cell oxidative burst as observed in some melanin producing epidemic strains of B. cenocepacia, protecting this pathogen from oxidative stress (Keith et al. 2007). ...
The production of black pigments in bacteria was discovered more than a century ago and related to tyrosine metabolism. However, their diverse biological roles and the control of melanin synthesis in different bacteria have only recently been investigated. The broad distribution of these pigments suggests that they have an important role in a variety of organisms. Melanins protect microorganisms from many environmental stress conditions, ranging from ultraviolet radiation and toxic heavy metals to oxidative stress. Melanins can also affect bacterial interactions with other organisms and are important in pathogenesis and survival in many environments. Bacteria produce several types of melanin through dedicated pathways or as a result of enzymatic imbalances in altered metabolic routes. The control of the melanin synthesis in bacteria involves metabolic and transcriptional regulation, but many aspects remain still largely unknown. The diverse properties of melanins have spurred a large number of applications, and recent efforts have been done to produce the pigment at biotechnologically relevant scales.
... Melanin can increase microbial virulence through two mechanisms: it reduces the susceptibility of the pathogen to host defense mechanisms and affects the host immune response to infection (Nosanchuk and Casadevall 2006). In melanogenic V. cholerae, pigment production increases cholera toxin and pilus expression, and enhances host colonization (Valeru et al. 2009). Due to its free radical scavenging potential, melanin can diminish host cell oxidative burst as observed in some melanin producing epidemic strains of B. cenocepacia, protecting this pathogen from oxidative stress (Keith et al. 2007). ...
The original version of this article contains error for some of the authors corrections were not included during correction stage especially for Table 1.
... The lack of a functional homogentisate 1,2-dioxygenase leads to accumulation of homogentisate in the tyrosine degradation pathway. Numerous reports described bacteria that produce the ochronotic pigment pyomelanin when homogentisate accumulates and undergoes oxidation and polymerization [30][31][32][33][34][35][36][37][38] . ...
... Several studies found pyomelanin functions that could enhance fitness in bacteria. Examples of these functions are protection against oxidative stress 30,36,48 or enhancement of bacterial virulence 35,38 . A V. cholerae mutant obtained by mini-Tn5 insertion within hmgA overproduced pyomelanin, expressed more toxin-coregulated pilus and cholera toxin, and showed enhanced colonization of intestines in an infant mice model of infection 38 . ...
... Examples of these functions are protection against oxidative stress 30,36,48 or enhancement of bacterial virulence 35,38 . A V. cholerae mutant obtained by mini-Tn5 insertion within hmgA overproduced pyomelanin, expressed more toxin-coregulated pilus and cholera toxin, and showed enhanced colonization of intestines in an infant mice model of infection 38 . On the other hand, other reports show a reduction in virulence of bacteria that develop the capability to produce the pigment 49 . ...
Vibrio anguillarum 531A, isolated from a diseased fish in the Atlantic Ocean, is a mixture composed of about 95 and 5% of highly pigmented cells (strain 531Ad) and cells with normal levels of pigmentation (strain 531Ac), respectively. Analysis of the V. anguillarum 531Ad DNA region encompassing genes involved in the tyrosine metabolism showed a 410-bp duplication within the hmgA gene that results in a frameshift and early termination of translation of the homogentisate 1,2-dioxygenase. We hypothesized that this mutation results in accumulation of homogentisate that is oxidized and polymerized to produce pyomelanin. Introduction in E. coli of recombinant clones carrying the V. anguillarum hppD (4-hydroxyphenylpyruvate-dioxygenase), and a mutated hmgA produced brown colored colonies. Complementation with a recombinant clone harboring hmgA restored the original color to the colonies confirming that in the absence of homogentisate 1,2-dioxygenase the intermediary in tyrosine catabolism homogentisate accumulates and undergoes nonenzymatic oxidation and polymerization resulting in high amounts of the brown pigment. Whole-genome sequence analysis showed that V. anguillarum 531 Ac and 531Ad differ in the hmgA gene mutation and 23 mutations, most of which locate to intergenic regions and insertion sequences.
... Melanin has various functions in diverse organisms and reportedly confers a survival advantage to microorganisms, especially under stressful environmental conditions, such as radiation, oxidative stress, the presence of digestive enzymes, and heavy metal toxicity (2). These molecules have also been associated with the virulence and pathogenicity of a variety of microbes, such as Cryptococcus neoformans, Wangiella (Exophiala) dermatitidis, and Vibrio cholerae (3)(4)(5), by protecting the pathogens against host defenses and interfering with the host immune response (2). Melanins are classified into several categories on the basis of their synthesis pathways, and bacteria usually synthesize two types, namely eumelanin or pyomelanin. ...
Aeromonas salmonicida subsp. s almonicida is the causative agent of furunculosis, a bacterial septicemia of cold-water fish of the Salmonidae family. Although other Aeromonas species can produce melanin, A. salmonicida subsp. salmonicida is the only member of this genus that has been reported to exhibit temperature-dependent melanization. Here, we demonstrated that thermosensitive melanogenesis in A. salmonicida subsp. salmonicida strains is due to the thermolability of 4-hydroxyphenylpyruvate dioxygenase (HppD). Additionally, we confirmed that this thermolabile HppD exhibited higher activity at low temperatures than its mesophilic homologues, suggesting this as an adaptive strategy of this enzyme to the psychrophilic lifestyle of A. salmonicida subsp. salmonicida . The strictly conserved hppD sequences among A. salmonicida subsp. salmonicida isolates and the specific possession of P103 and L119 residues could be used as a reference for the identification of A. salmonicida subsp. salmonicida isolates.
