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Pseudanabaena galeata. Strain UTEX SP44. Fig. 14. Light micrographs showing single filaments. Scale bar ¼ 10 lm. Figs 15-16. TEM. Fig. 15. Transverse section showing parietal arrangement of four to five thylakoids. Scale bar ¼ 0.2 lm. Fig. 16. Longitudinal section. Note cyanophycin granules and parallel thylakoids. Scale bar ¼ 0.5 lm. Figs 17-18. Pseudanabaena catenata. Strain SAG 1464-1. TEM. Fig. 17. Transverse section showing parietal arrangement with four thylakoids. Scale bar ¼ 0.5 lm. Fig. 18. Longitudinal section showing parallel thylakoids and constrictions with cross walls. Scale bar ¼ 1 lm.
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A freshwater cyanobacterium from Hoamy Reservoir, Hue, Vietnam was isolated into clonal culture (April 2004). Based on general morphology (including size and shape) from light microscopy it was identified as Pseudanabaena cf. moniliformis. However, transmission electron microscopy revealed the thylakoids to be radially arranged, in contrast to the...
Citations
... The genus Annamia was described with the type species A. toxica. This genus was assigned to the family Borziaceae within the order Oscillatoriales [1], because it has radially arranged thylakoids and forms filamentous colonies like the genus Pseudanabaena. Tuji et al. [2] described the second member of this genus as A. dubia from Lake Kasumigaura Japan. ...
... In the phylogenetic tree using 16S rRNA and ITS region, the genus Annamia matched the clade that had been assigned to 'Cyanobacteriaceae' [3], including the genera Cyanobacterium, Geminobacterium and Geminocystis. Due to International Code of Nomenclature for algae, fungi, and plants (ICN) rule issues, 'Cyanobacteriaceae' was renamed Geminocystaceae [1] within the order Chroococcales [2]. The order Chroococcales has eight families [4] which are characterized by coccoid forms or pseudo-filaments with sheaths [3] [5] and irregular thylakoid arrangement [3]. ...
... The genus Annamia is only one exception to the order Chroococcales in forming true filamentous colonies. No cultured strains of A. toxica remain [1], and a cultured strain of A. dubia (NIES-4383) is the only cultivated strain of this genus. This genus is also an exception in the Chroococcus family, which contains Microcystin. ...
The complete genome of Annamia dubia was sequenced. The genome size is 4.02 Mbp, including 3886286 bp circular chromosome and four circular plasmids (31516, 42453, 38085 and 24903 bp). It included 3718 protein-coding sequences, 45 tRNA genes, three sets of rRNA genes, a microcystin biosynthesis gene cluster and six CRISPR (clustered regularly interspaced short palindromic repeat). Annamia is the only one genus in the Chroococcales that makes filamentous colonies. FraC and FraG were identified in the genome. These genes are required for the integrity of cell junctions and influencing filament integrity and are thought to be related to colony formation. These genes are first reported from Chroococcales, and may play a significant role in the colony formation of this species.
In the phylogenetic tree of the FraC gene, A. dubia was located in the basal position of Oscillatoriales. The GC ratio of FraC gene of A. dubia is very low from the genome and the FraC gene of Microcoleaceae. The presence of these genes in the basal region and the low GC ratio suggests that the FraC gene in this species was introduced by horizontal gene transfer. Since the filamentous colony is a fundamental and important taxonomic feature for the classification of cyanobacteria, the possibility of horizontal transmission of genes involved in filamentous cyanobacterial colonies is an important discovery for the classification of cyanobacteria.
... The genus Annamia, in contrast to abovementioned unicellular genera, is represented by filamentous species A. toxica (Nguyen et al. 2013) and A. dubia (Tuji et al. 2021). Although great distinction between unicellularity and producing trichome was against belonging to one and the same taxon in the outdated phenotypic system , modern taxonomy of cyanobacteria issues from the supremacy of phylogeny-based approach. ...
... Lamellar systems in filamentous species A. toxica and A. dubia are similar to those in many filamentous nonheterocystous cyanobacteria as well as in some unicellular strains (Hoffmann et al. 2005). Namely, thylakoids orient perpendicularly to plasma membrane in crosssection micrographs while in longitudinal projection they lie in parallel to it (Nguyen et al. 2013, Tuji et al. 2021. ...
Progress in phylogenomic analysis has led to a considerable re-evaluation of former cyanobacterial system, with many new taxa being established at different nomenclatural levels. The family Geminocystaceae is among cyanobacterial taxa recently described on the basis of polyphasic approach. Within this family, there are six genera: Geminocystis, Cyanobacterium, Geminobacterium, Annamia, Picocyanobacterium, and Microcrocis. The genus Geminocystis previously encompassed two species: G. herdmanii and G. papuanica. Herein, a new species G. urbisnovae was proposed under the provision of the International Code of Nomenclature for algae, fungi, and plants (ICN). Polyphasic analysis was performed for five strains from the CALU culture collection (St. Petersburg State University, Russian Federation), and they were assigned to the genus Geminocystis in accordance with high 16S rRNA gene similarity to existing species, as well as because of proximity to these species on the phylogenetic trees reconstructed with RaxML and Bayes methods. Plausibility of their assignment to a separate species of the genus Geminocystis was substantiated with smaller cell size; stenohaline freshwater ecotype; capability to complementary chromatic adaptation of second type (CA2); distinct 16S rRNA gene clustering; sequences and folding of D1−D1′ and B box domains of the 16S−23S internal transcribed spacer region. The second objective pursued by this communication was to provide a survey of the family Geminocystaceae. The overall assessment was that, despite attention of many researchers, this cyanobacterial family has been understudied and, especially in the case of the crucially important genus Cyanobacterium, taxonomically problematic.
... The cell shape of Geminobacterium and Geminocystis is spherical, Cyanobacterium is shortly oval or rod-like (Oren et al. 2022), Picosynechococcus is stretched oval . Prolonged cylindrical cells are connected in short pseudofilaments in Annamia (Lien et al. 2013). Filamentous strains such as Leptolyngbya sp. ...
Cyanobacterial taxonomy is facing a period of rapid changes thanks to the ease of 16S rRNA gene sequencing and established workflows for description of new taxa. Since the last comprehensive review of the cyanobacterial system in 2014 until 2021, at least 273 species in 140 genera were newly described. These taxa were mainly placed into previously defined orders and families although several new families were proposed. However, the classification of most taxa still relied on hierarchical relationships inherited from the classical morphological taxonomy. Similarly, the obviously polyphyletic orders such as Synechococcales and Oscillatoriales were left unchanged. In the current study, the rising number of genomic sequences of cyanobacteria and well described reference strains allowed us to reconstruct a robust phylogenomic tree for taxonomic purposes. A less robust but better sampled 16S rRNA gene phylogeny was mapped to the phylogenomic backbone. Based on both these phylogenies, a polyphasic classification throughout the whole phylum of Cyanobacteria was created, with ten new orders and fifteen new families. The proposed system of cyanobacterial orders and families relied on a phylogenomic tree but still employed phenotypic apomorphies where possible to make it useful for professionals in the field. It was, however, confirmed that morphological convergence of phylogenetically distant taxa was a frequent phenomenon in cyanobacteria. Moreover, the limited phylogenetic informativeness of the 16S rRNA gene, resulting in ambiguous phylogenies above the genus level, emphasized the integration of genomic data as a prerequisite for the conclusive taxonomic placement of a vast number of cyanobacterial genera in the future.
... As the large family of the order Oscillatoriales, Microcoleaceae contains numerous genera. Among those are the genera Annamia Nguyen (Nguyen et al. 2013), Kamptonema Strunecký et al. (2014: 203), Roseofilum Casamatta et al. (2012: 494) included in a well-described group based upon molecular characterization and modern criteria. Several older genera including the genus Microcoleus Desmazières ex Gomont (1892: 350) are monophyletically documented in a successful way. ...
Porphyrosiphon annulatus sp. nov. belonging to Microcoleaceae, Oscillatoriales was collected from the moist soil under the rock in the Gwanggyo Mountain of Suwon City, Gyeonggi Province, Korea and cultured. Using the raw and cultured samples of the collected strains, we observed their morphological features through LM and TEM. Furthermore, their 16S rRNA gene and 16S–23S rRNA intergenic transcribed spacer (ITS) sequences were determined to be used phylogenetic analyses. We affirmed that thick sheath of the cells possessed transversely annular and longitudinal lamellations. The ultrastructure of thylakoids was a radial arrangement, which corresponds with a characteristic of the Microcoleaceae. In addition, P. annulatus displays the most similar morphology with type species P. notarisii; however, it differently holds the transversely annular lamellations with a shorter cell length and relatively dense trichome. Our 16S rRNA gene phylogeny showed that P. annulatus formed a clade with P. notarisii, and their DNA similarity was calculated to be 96.2%. The family Microcoleaceae was found to be paraphyletic with a distinct linage of the genus Porphyrosiphon. The ITS sequence of P. annulatus was unique in length and nucleotide composition, with different secondary structures of D1–D1ʹ and Box-B helices compared to those of close relatives. Overall, morphology and genetic traits of the Korean Porphyrosiphon suggest that P. annulatus should be considered to be a novel species.
... Ecological Indicators 117 (2020) 106695 coccoid colonies were always degraded into single cells when processing field samples with Lugol's iodine solution, and this could lead coccoid cyanobacteria misidentified as colony was a diagnostic character for distinguishing them . Filamentous Annamia morphologically resembled Pseudanabaena, they could be misidentified for their difference in the thylakoid arrangement that could not be observed under microscope (Nguyen et al., 2013). The gas-vacuolated oscillatorioid Aerosakkonema, Cephalothrix, Planktothrix and Planktothricoides could be misidentified as Oscillatoria for gas vacuoles were always invisible in the samples for morphological inspection . ...
In processing metabarcoding data from the 16S rRNA amplicon sequencing, OTUs were commonly binned at 97% similarity, the criteria was once proposed as the limit for species delimitation for prokaryotes. This numeric guide is rather a tunable parameter and has recently been revised and increased up to 99% threshold facilitated with more 16S rRNA sequences available. In the study, we updated 97% identity to 99% in combination with monophyletic species concept rather than OTUs to evaluate cyanobacterial diversity from 11 freshwaters using metabarcoding technique. The cyanobacterial OTUs were first determined by aligning to the SILVA database, and further reassigned through the evolutionary placement algorithm (EPA). Inferred from the EPA, metabarcoding found diverse cyanobacterial community with at least 70 monophyletic species (113 OTUs) from 18 coccoid, 14 simple filamentous, 10 heterocytous genera, and Prochlorothrix by clustering OTUs at 97% similarity. When updating to 99% similarity, 5 cryptic genera were detected with 3 of them should be revised as new genera for they achieved monophyly in the phylogeny. In addition, updating to 99% similarity also detected 48 cryptic monophyletic species from 9 genera. In conclusion, updating 97% identity to 99% in combination with monophyletic species found cryptic genera and species, and provided a much clearer separation of cyanobacterial community between lakes and reservoirs and also between seasons. The combined methods improved the use of metabarcoding technique to elucidate field cyanobacterial community.
... Fine-scale morphological differences also complicated identifications. Annamia was morphologically similar to Pseudanabaena, but it showed a different arrangement of thylakoid and these genera were placed in different clusters of a phylogeny inferred from multiple genes (Nguyen et al., 2013). The arrangement of thylakoid could not be observed under a microscope, so Annamia could be misidentified as Pseudanabaena. ...
Next generation sequencing has become a popular method to identify cyanobacterial diversity in ecosystems. Morphological identification poses challenges in deciphering cyanobacterial diversity because phenotypic variations can be misleading, picocyanobacteria are ignored easily, specialists familiar with classification systems are lacking, and updates of taxonomic treatises are not shared in a timely manner or adopted by researchers engaged in monitoring of phytoplankton. In this study, metabarcoding of 54 samples from 7 freshwater systems yielded saturated cyanobacterial sequences, and the compositions of the resulting communities were compared with a dataset generated by morphological identification. A total of 69 cyanobacterial operational taxonomic units (OTUs) were finally codetermined through the ribosomal database project (RDP) via the Silva database and blast analysis using a database maintained by the National Center for Biotechnology Information (NCBI). Blast resolved more OTUs, with 1 and 27 OTUs identified at the species level and 35 and 9 OTUs identified at the genus levels through Silva and NCBI, respectively. Only 13 OTUs were matched at genus levels by these two methods. The accuracy of blast was further verified through molecular phylogeny. Blast results were compared with morphological identification at the genus level. Each method identified 26 genera, and 12 genera were shared by both methods. Half of the genera only identified by metabarcoding have been described recently, and data on morphologically diagnostic characters were not available. Some genera shared morphological similarities, which led them to be misidentified. Ten of the 12 genera found by both methods yielded less than 2 morphological mismatches. These genera produced a higher proportion of occurrences in metabarcoding, which was indicative of higher sensitivity to cyanobacteria. A larger number of species were found in metabarcoding (8–38 OTUs) than in morphological surveys (1–16 morphospecies), nevertheless, the results were positively correlated (R² = 0.56, p < 0.001). Metabarcoding yielded data that produced a clearer separation of cyanobacterial communities from different systems and seasons as seen in non-metric multidimensional scaling (nMDS) and canonical analysis of principal coordinates (CAP) ordinations. In conclusion, metabarcoding could provide a more accurate picture of cyanobacterial communities.
... Although very conspicuous, radial thylakoid architecture does not serve as a suitable taxonomic marker. It seems to have serially emerged in a number of genera of the phylogenetically overlapping families Coleofasciculaceae (Casamatta et al., 2012, Figures 2A,B), Microcoleaceae (Porta et al., 2003;Chatchawan et al., 2012;Nguyen et al., 2013;Strunecký et al., 2013;Cellamare et al., 2018;Figures 2B,C), and Oscillatoriaceae (Ridley et al., 2005;Lokmer, 2007;Rasoulouniriana et al., 2009;Martins et al., 2016). In spite of a possible common tendency to form radial thylakoids in certain lineages, they usually occur in individual strains, intermixed with strains exhibiting other arrangements (Figure 8). ...
While photosynthetic processes have become increasingly understood in cyanobacterial model strains, differences in the spatial distribution of thylakoid membranes among various lineages have been largely unexplored. Cyanobacterial cells exhibit an intriguing diversity in thylakoid arrangements, ranging from simple parietal to radial, coiled, parallel, and special types. Although metabolic background of their variability remains unknown, it has been suggested that thylakoid patterns are stable in certain phylogenetic clades. For decades, thylakoid arrangements have been used in cyanobacterial classification as one of the crucial characters for definition of taxa. The last comprehensive study addressing their evolutionary history in cyanobacteria was published 15 years ago. Since then both DNA sequence and electron microscopy data have grown rapidly. In the current study, we map ultrastructural data of >200 strains onto the SSU rRNA gene tree, and the resulting phylogeny is compared to a phylogenomic tree. Changes in thylakoid architecture in general follow the phylogeny of housekeeping loci. Parietal arrangement is resolved as the original thylakoid organization, evolving into complex arrangement in the most derived group of heterocytous cyanobacteria. Cyanobacteria occupying intermediate phylogenetic positions (greater filamentous, coccoid, and baeocytous types) exhibit fascicular, radial, and parallel arrangements, partly tracing the reconstructed course of phylogenetic branching. Contrary to previous studies, taxonomic value of thylakoid morphology seems very limited. Only special cases such as thylakoid absence or the parallel arrangement could be used as taxonomically informative apomorphies. The phylogenetic trees provide evidence of both paraphyly and reversion from more derived architectures in the simple parietal thylakoid pattern. Repeated convergent evolution is suggested for the radial and fascicular architectures. Moreover, thylakoid arrangement is constrained by cell size, excluding the occurrence of complex architectures in cyanobacteria smaller than 2 μm in width. It may further be dependent on unknown (eco)physiological factors as suggested by recurrence of the radial type in unrelated but morphologically similar cyanobacteria, and occurrence of special features throughout the phylogeny. No straightforward phylogenetic congruences have been found between proteins involved in photosynthesis and thylakoid formation, and the thylakoid patterns. Remarkably, several postulated thylakoid biogenesis factors are partly or completely missing in cyanobacteria, challenging their proposed essential roles.
... Although very conspicuous, radial thylakoid architecture does not serve as a suitable taxonomic marker. It seems to have serially emerged in a number of genera of the phylogenetically overlapping families Coleofasciculaceae (Casamatta et al., 2012, Figures 2A,B), Microcoleaceae (Porta et al., 2003;Chatchawan et al., 2012;Nguyen et al., 2013;Strunecký et al., 2013;Cellamare et al., 2018;Figures 2B,C), and Oscillatoriaceae (Ridley et al., 2005;Lokmer, 2007;Rasoulouniriana et al., 2009;Martins et al., 2016). In spite of a possible common tendency to form radial thylakoids in certain lineages, they usually occur in individual strains, intermixed with strains exhibiting other arrangements (Figure 8). ...
While photosynthetic processes have become increasingly understood in cyanobacterial model strains, differences in the spatial distribution of thylakoid membranes among various lineages have been largely unexplored. Cyanobacterial cells exhibit an intriguing diversity in thylakoid arrangements, ranging from simple parietal to radial, coiled, parallel, and special types. Although metabolic background of their variability remains unknown, it has been suggested that thylakoid patterns are stable in certain phylogenetic clades. For decades, thylakoid arrangements have been used in cyanobacterial classification as one of the crucial characters for definition of taxa. The last comprehensive study addressing their evolutionary history in cyanobacteria was published 15 years ago. Since then both DNA sequence and electron microscopy data have grown rapidly. In the current study, we map ultrastructural data of >200 strains onto the SSU rRNA gene tree, and the resulting phylogeny is compared to a phylogenomic tree. Changes in thylakoid architecture in general follow the phylogeny of housekeeping loci. Parietal arrangement is resolved as the original thylakoid organization, evolving into complex arrangement in the most derived group of heterocytous cyanobacteria. Cyanobacteria occupying intermediate phylogenetic positions (greater filamentous, coccoid, and baeocytous types) exhibit fascicular, radial, and parallel arrangements, partly tracing the reconstructed course of phylogenetic branching. Contrary to previous studies, taxonomic value of thylakoid morphology seems very limited. Only special cases such as thylakoid absence or the parallel arrangement could be used as taxonomically informative apomorphies. The phylogenetic trees provide evidence of both paraphyly and reversion from more derived architectures in the simple parietal thylakoid pattern. Repeated convergent evolution is suggested for the radial and fascicular architectures. Moreover, thylakoid arrangement is constrained by cell size, excluding the occurrence of complex architectures in cyanobacteria smaller than 2 µm in width. It may further be dependent on unknown (eco)physiological factors as suggested by recurrence of the radial type in unrelated but morphologically similar cyanobacteria, and occurrence of special features throughout the phylogeny. No straightforward phylogenetic congruences have been found between proteins involved in photosynthesis and thylakoid formation, and the thylakoid patterns. Remarkably, several postulated thylakoid biogenesis factors are partly or completely missing in cyanobacteria, challenging their proposed essential roles.
... This result is consistent with an investigation in Baihua reservoir, in southwestern China (Li et al. 2013). Pseudoanabaena sp. has been frequently reported to be cyanobacteria bloom components, which can not only produce microcystins but also cause T&O problems (Marsalek et al. 2003;Nguyen et al. 2013). In this study, high concentrations of 2-MIB were found in water with high abundance of Pseudoanabaena sp., which has been recognized as a potential cause of off-flavor in water supplies since the early 1990s (Izaguirre et al. 1999). ...
With the increasing occurrence of water eutrophication and blooms, earthy-musty odor problems caused by cyanobacteria have been more and more apparent. These problems have a serious impact on aquatic ecosystems and drinking water safety and become one of the priorities of the water environment researches and managements. In the present study, genes associated with 2-MIB synthesis in cyanobacteria were studied by systematic investigation on molecular characterization and quantity of 2-MIB-producing cyanobacteria in China. Our results founded that Pseudoanabaena is an important 2-MIB-producing phytoplankton and predominant in summer in Qingcaosha reservoir, and the copy number of mic and 2-MIB concentration have strongly positive correlation. We also demonstrated that abundance of mic in water was significant correlation with that in sediment. These results will help us to understand the main taxa of the odoriferous cyanobacteria in the water bodies in China, understand the genetic basis of the odor substances in the cyanobacteria. Rapid, reliable monitoring and ecological research methods for the production of odor cyanobacteria in water bodies can be established based on these results.
... et sp. nov., which display concentric thylakoids (Nguyen et al., 2013), these structures are irregularly arranged in C. raciborskii (Figures 3F and 4,Ai). ...
Cyanobacteria are aquatic photosynthetic microorganisms. While of enormous ecological importance, they have also been linked to human and animal illnesses around the world as a consequence of toxin production by some species. Cylindrospermopsis raciborskii, a filamentous nitrogen-fixing cyanobacterium, has attracted considerable attention due to its potential toxicity and ecophysiological adaptability. We investigated whether C. raciborskii could be affected by ultraviolet (UV) radiation. Non-axenic cultures of C. raciborskii were exposed to three UV treatments (UVA, UVB, or UVA + UVB) over a 6 h period, during which cell concentration, viability and ultrastructure were analyzed. UVA and UVA + UVB treatments showed significant negative effects on cell concentration (decreases of 56.4 and 64.3%, respectively). This decrease was directly associated with cell death as revealed by a cell viability fluorescent probe. Over 90% of UVA + UVB- and UVA-treated cells died. UVB did not alter cell concentration, but reduced cell viability in almost 50% of organisms. Transmission electron microscopy (TEM) revealed a drastic loss of thylakoids, membranes in which cyanobacteria photosystems are localized, after all treatments. Moreover, other photosynthetic- and metabolic-related structures, such as accessory pigments and polyphosphate granules, were damaged. Quantitative TEM analyses revealed a 95.8% reduction in cell area occupied by thylakoids after UVA treatment, and reduction of 77.6 and 81.3% after UVB and UVA + UVB treatments, respectively. Results demonstrated clear alterations in viability and photosynthetic structures of C. raciborskii induced by various UV radiation fractions. This study facilitates our understanding of the subcellular organization of this cyanobacterium species, identifies specific intracellular targets of UVA and UVB radiation and reinforces the importance of UV radiation as an environmental stressor.
