Fatty Acid Composition of Planktonic Species of Anabaena (Cyanobacteria) with Coiled Trichomes Exhibited a Significant Taxonomic Value

Biogeography of bloom-forming microcystin producing and non-toxigenic populations of Dolichospermum lemmermannii (Cyanobacteria)

In the last decades, the cyanobacterium Dolichospermum lemmermannii showed an increasing spread to Southern Europe, raising serious concerns due to its ability to produce cyanotoxins. The widening of its geographic distribution and the observation of strains showing high optimum temperature underline its ecological heterogeneity, suggesting the existence of different ecotypes. To investigate its biogeography, new isolates from different European water bodies, together with strains maintained by the Norwegian Institute for Water Research Culture Collection of Algae, were genetically characterised for the 16S rRNA gene and compared with strains obtained from public repositories. Geographic distance highly influenced the differentiation of genotypes, further suggesting the concurrent role of geographic isolation, physical barriers and environmental factors in promoting the establishment of phylogenetic lineages adapted to specific habitats. Differences among populations were also examined by morphological analysis and evaluating the toxic potential of single strains, which revealed the exclusive ability of North European strains to produce microcystins, whereas the populations in Southern Europe tested negative for a wide range of cyanotoxins. The high dispersion ability and the existence of toxic genotypes indicate the possible spread of harmful blooms in other temperate regions.

Identification of a new-to-science cyanobacterium, Toxifilum mysidocida gen. nov. & sp. nov. (Cyanobacteria, Cyanophyceae)

Cyanobacteria occupy many niches within terrestrial, planktonic, and benthic habitats. The diversity of habitats colonized, similarity of morphology, and phenotypic plasticity all contribute to the difficulty of cyanobacterial identification. An unknown marine filamentous cyanobacterium was isolated from an aquatic animal rearing facility having mysid mortality events. The cyanobacterium originated from Corpus Christi Bay, TX. Filaments are rarely solitary, benthic mat forming, unbranched, and narrowing at the ends. Cells are 2.1 × 3.1 μm (width × length). Thylakoids are peripherally arranged on the outer third of the cell; cyanophycin granules and polyphosphate bodies are present. Molecular phylogenetic analysis in addition to morphology (transmission electron microscopy and scanning electron microscopy) and chemical composition all confirm it as a new genus and species we name Toxifilum mysidocida. At least one identified Leptolyngbya appears (based on genetic evidence and TEM) to belong to this new genus.

Modes of Fatty Acid desaturation in cyanobacteria: an update

Fatty acid composition of individual species of cyanobacteria is conserved and it may be used as a phylogenetic marker. The previously proposed classification system was based solely on biochemical data. Today, new genomic data are available, which support a need to update a previously postulated FA-based classification of cyanobacteria. These changes are necessary in order to adjust and synchronize biochemical, physiological and genomic data, which may help to establish an adequate comprehensive taxonomic system for cyanobacteria in the future. Here, we propose an update to the classification system of cyanobacteria based on their fatty acid composition.

Microscopic, molecular, and biochemical investigations to characterize a benthic cyanoprokaryote Leptolyngbya strain from Egypt

Microscopic, molecular, and biochemical investigations were conducted to describe a benthic mat-forming Leptolyngbya isolate collected from wastewater canal in Helwan area, Egypt. Microscopic examination revealed that the isolate was filamentous, nonheterocystous, with obvious granular surface ornamentation. Electron microscopy was used to reveal the isolate's ultrastructure. Cross walls were thick with uneven deposition. Thylakoids were convoluted and irregularly distributed. Granular content differed from one cell to the other probably due to their physiological stages/position within the filaments and/or their age. Nycridial cells were present. Highly refractile gas vesicle-like structures were detected and their identity as gas vesicles was confirmed by amplifying the gene coding for the gas vesicle protein GvpA. The presence of gas vesicles in benthic microorganisms is intriguing, and it is possible that those vesicles serve as a floating and dispersal mechanism as they increase in filaments that are about to break and release vacuolated hormogonia. To further confirm the isolate's identity, molecular analysis using 16S rRNA gene was performed. The sequence showed only 94% similarity to Leptolyngbya badia and less than 92% to other leptolyngbya. The phylogenetic analyses showed the coclustering of this strain with other Leptolyngbya strain. The fatty acid composition, used as a chemotaxonomic marker, revealed the presence of a considerable amount of polyunsaturated acids. Nevertheless, saturated fatty acids represented the highest proportion of the total fatty. Surprisingly, fatty acids of relatively limited occurrence within oscillatorian cyanobacteria such as saturated myristic fatty acid and polyunsaturated fatty acid C16:3 were found.

Chemotaxonomy of heterocystous cyanobacteria using FAME profiling as species markers

The fatty acid methyl ester (FAME) analysis of the 12 heterocystous cyanobacterial strains showed different fatty acid profiling based on the presence/absence and the percentage of 13 different types of fatty acids. The major fatty acids viz. palmitic acid (16:0), hexadecadienoic acid (16:2), stearic acid (18:0), oleic acid (18:1), linoleic (18:2), and linolenic acid (18:3) were present among all the strains except Cylindrospermum musicola where oleic acid (18:1) was absent. All the strains showed high levels of polyunsaturated fatty acid (PUFAs; 41-68.35%) followed by saturated fatty acid (SAFAs; 1.82-40.66%) and monounsaturated fatty acid (0.85-24.98%). Highest percentage of PUFAs and essential fatty acid (linolenic acid; 18:3) was reported in Scytonema bohnerii which can be used as fatty acid supplement in medical and biotechnological purpose. The cluster analysis based on FAME profiling suggests the presence of two distinct clusters with Euclidean distance ranging from 0 to 25. S. bohnerii of cluster I was distantly related to the other strains of cluster II. The genotypes of cluster II were further divided into two subclusters, i.e., IIa with C. musicola showing great divergence with the other genotypes of IIb which was further subdivided into two groups. Subsubcluster IIb(1) was represented by a genotype, Anabaena sp. whereas subsubcluster IIb(2) was distinguished by two groups, i.e., one group having significant similarity among their three genotypes showed distant relation with the other group having closely related six genotypes. To test the validity of the fatty acid profiles as a marker, cluster analysis has also been generated on the basis of morphological attributes. Our results suggest that FAME profiling might be used as species markers in the study of polyphasic approach based taxonomy and phylogenetic relationship.

POLYPHASIC CHARACTERIZATION OF DOLICHOSPERMUM SPP. AND SPHAEROSPERMOPSIS SPP. (NOSTOCALES, CYANOBACTERIA): MORPHOLOGY, 16S rRNA GENE SEQUENCES AND FATTY ACID AND SECONDARY METABOLITE PROFILES(1)

The genera Dolichospermum (Ralfs ex Bornet et Flahault) Wacklin, L. Hoffm. et Komárek and Sphaerospermopsis Zapomělová, Jezberová, Hrouzek, Hisem, K. Řeháková et Komárk.-Legn. represent a highly diversified group of planktonic cyanobacteria that have been recently separated from the traditional genus Anabaena Bory ex Bornet et Flahault. In this study, morphological diversity, phylogeny of the 16S rRNA gene, production of fatty acids, and secondary metabolite profiles were evaluated in 33 strains of 14 morphospecies isolated from the Czech Republic. Clustering of the strains based on 16S rRNA gene sequences corresponded to wider groups of species in terms of morphology. The overall secondary metabolite and fatty acid profiles, however, were not correlated to each other and neither were they correlated to the 16S rRNA phylogeny nor the morphology of the strains. Nevertheless, a minor part of the detected secondary metabolites (19% of all compounds) was present only in close relatives and can be thus considered as autapomorphic features.

POLYPHASIC CHARACTERIZATION OF THREE STRAINS OF ANABAENA RENIFORMIS AND APHANIZOMENON APHANIZOMENOIDES (CYANOBACTERIA) AND THEIR RECLASSIFICATION TO SPHAEROSPERMUM GEN. NOV. (INCL. ANABAENA KISSELEVIANA)(1)

Occurrences of rare cyanobacteria Anabaena reniformis Lemmerm. and Aphanizomenon aphanizomenoides (Forti) Horecká et Komárek were recently detected at several localities in the Czech Republic. Two monoclonal strains of An. reniformis and one strain of Aph. aphanizomenoides were isolated from distant localities and different sampling years. They were characterized by a combination of morphological, genetic, and biochemical approaches. For the first time, partial 16S rRNA gene sequences were obtained for these morphospecies. Based on this gene, all of these strains clustered separately from other planktonic Anabaena and Aphanizomenon strains. They appeared in a cluster with Cylindrospermopsis Seenaya et Subba Raju and Raphidiopsis F. E. Fritsch et M. F. Rich, clustered closely together with two An. kisseleviana Elenkin strains available from GenBank. A new generic entity was defined (Sphaerospermum gen. nov., with the type species S. reniforme, based on the traditional species An. reniformis). These results contribute significantly to the knowledge base about genetic heterogeneity among planktonic Anabaena-like and Aphanizomenon-like morphospecies. Accordingly, the subgenus Dolichospermum, previously proposed for the group of planktonic Anabaena, should be revaluated. Secondary metabolite profiles of the An. reniformis and Aph. aphanizomenoides strains differed considerably from 17 other planktonic Anabaena strains of eight morphospecies isolated from Czech water bodies. Production of puwainaphycin A was found in both of the An. reniformis strains. Despite the relatively short phylogenetic distance from Cylidrospermopsis, the production of cylindrospermopsin was not detected in any of our strains.

Omega-3 fatty acids are oxygenated at the n-7 carbon by the lipoxygenase domain of a fusion protein in the cyanobacterium Acaryochloris marina

Lipoxygenases (LOX) are found in most organisms that contain polyunsaturated fatty acids, usually existing as individual genes although occasionally encoded as a fusion protein with a catalase-related hemoprotein. Such a fusion protein occurs in the cyanobacterium Acaryochloris marina and herein we report the novel catalytic activity of its LOX domain. The full-length protein and the C-terminal LOX domain were expressed in Escherichia coli, and the catalytic activities characterized by UV, HPLC, GC-MS, and CD. All omega-3 polyunsaturates were oxygenated by the LOX domain at the n-7 position and with R stereospecificity: alpha-linolenic and the most abundant fatty acid in A. marina, stearidonic acid (C18.4omega3), are converted to the corresponding 12R-hydroperoxides, eicosapentaenoic acid to its 14R-hydroperoxide, and docosahexaenoic acid to its 16R-hydroperoxide. Omega-6 polyunsaturates were oxygenated at the n-10 position, forming 9R-hydroperoxy-octadecadienoic acid from linoleic acid and 11R-hydroperoxy-eicosatetraenoic acid from arachidonic acid. The metabolic transformation of stearidonic acid by the full-length fusion protein entails its 12R oxygenation with subsequent conversion by the catalase-related domain to a novel allene epoxide, a likely precursor of cyclopentenone fatty acids or other signaling molecules (Gao et al, J. Biol. Chem. 284:22087-98, 2009). Although omega-3 fatty acids and lipoxygenases are of widespread occurrence, this appears to be the first description of a LOX-catalyzed oxygenation that specifically utilizes the terminal pentadiene of omega-3 fatty acids.

A 49-kDa mini-lipoxygenase from Anabaena sp. PCC 7120 retains catalytically complete functionality

Anabaena sp. PCC 7120 is one of the few prokaryotes harboring a lipoxygenase (LOX) gene. The sequence resides in an open reading frame encoding a fusion protein of a catalase-like hemoprotein with an unusually short LOX (approximately 49 kDa) at the C terminus. The recombinant mini-LOX contains a non-heme iron in the active site and is highly active with linoleic and alpha-linolenic acids (which occur naturally in Anabaena) giving the respective 9R-hydroperoxides, the mirror image of the 9S-LOX products of plants. Using stereospecifically labeled [11-(3)H]linoleic acids we show that reaction is catalyzed via a typical antarafacial relationship of initial hydrogen abstraction and oxygenation. The mini-LOX oxygenated C16/C18:2-phosphatidylcholine with 9R specificity, suggesting a "tail first" mode of fatty acid binding. Site-directed mutagenesis of an active site Ala (Ala215), typically conserved as Gly in R-LOX, revealed that substitution with Gly retained 9R specificity, whereas the larger Val substitution switched oxygenation to 13S, implying that Ala215 represents the functional equivalent of the Gly in other R-LOX. Metabolism studies using a synthetic fatty acid with extended double bond conjugation, 9E,11Z,14Z-20:3omega6, showed that the mini-LOX can control oxygenation two positions further along the fatty acid carbon chain. We conclude that the mini-LOX, despite lacking the beta-barrel domain and much additional sequence, is catalytically complete. Interestingly, animal and plant LOX, which undoubtedly share a common ancestor, are related in sequence only in the catalytic domain; it is possible that the prokaryotic LOX represents a common link and that the beta-barrel domain was then acquired independently in the animal and plant kingdoms.

Enzymatic synthesis of a bicyclobutane fatty acid by a hemoprotein lipoxygenase fusion protein from the cyanobacterium Anabaena PCC 7120

Biological transformations of polyunsaturated fatty acids often lead to chemically unstable products, such as the prostaglandin endoperoxides and leukotriene A(4) epoxide of mammalian biology and the allene epoxides of plants. Here, we report on the enzymatic production of a fatty acid containing a highly strained bicyclic four-carbon ring, a moiety known previously only as a model compound for mechanistic studies in chemistry. Starting from linolenic acid (C18.3omega3), a dual function protein from the cyanobacterium Anabaena PCC 7120 forms 9R-hydroperoxy-C18.3omega3 in a lipoxygenase domain, then a catalase-related domain converts the 9R-hydroperoxide to two unstable allylic epoxides. We isolated and identified the major product as 9R,10R-epoxy-11trans-C18.1 containing a bicyclo[1.1.0]butyl ring on carbons 13-16, and the minor product as 9R,10R-epoxy-11trans,13trans,15cis-C18.omega3, an epoxide of the leukotriene A type. Synthesis of both epoxides can be understood by initial transformation of the hydroperoxide to an epoxy allylic carbocation. Rearrangement to an intermediate bicyclobutonium ion followed by deprotonation gives the bicyclobutane fatty acid. This enzymatic reaction has no parallel in aqueous or organic solvent, where ring-opened cyclopropanes, cyclobutanes, and homoallyl products are formed. Given the capability shown here for enzymatic formation of the highly strained and unstable bicyclobutane, our findings suggest that other transformations involving carbocation rearrangement, in both chemistry and biology, should be examined for the production of the high energy bicyclobutanes.