title: Unveiling of novel radiations within Trichodesmium cluster by hetR gene sequence analysis.
abstract: The filamentous nonheterocystous cyanobacterial genus Katagnymene is a common diazotrophic component of tropical and subtropical oceans. To assess the phylogenetic affiliation of this taxon, two partial 16S rRNA gene sequences and 25 partial hetR gene sequences originating from the genera Katagnymene and Trichodesmium collected from open, surface waters of the Atlantic, Indian, and Pacific oceans were compared. Single trichomes or colonies were identified morphologically by using light microscopy and then used directly as templates in hetR PCR analyses. In addition, three cultured strains, identified as Katagnymene pelagica, Katagnymene spiralis, and Trichodesmium sp., were examined. The data show that the genus Katagnymene is in the Trichodesmium cluster and that K. pelagica Lemmermann and K. spiralis Lemmermann are most likely one species, despite their different morphologies. Phylogenetic analyses also unveiled four distinct clusters in the Trichodesmium cluster, including one novel cluster. Our findings emphasize the conclusion that known morphological traits used to differentiate marine nonheterocystous cyanobacteria at the genus and species levels correlate poorly with genetic data, and a revision is therefore suggested.
authors.affiliation: Department of Botany, Stockholm University, Stockholm, Sweden.
authors.forename: Pernilla
authors.initials: P
authors.lastname: Lundgren
authors.forename: Sven
authors.initials: S
authors.lastname: Janson
authors.forename: Sara
authors.initials: S
authors.lastname: Jonasson
authors.forename: Alon
authors.initials: A
authors.lastname: Singer
authors.forename: Birgitta
authors.initials: B
authors.lastname: Bergman
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D000458:Cyanobacteria / Q000145:classification* / Q000235:genetics*; D004269:DNA, Bacterial / Q000032:analysis; D004275:DNA, Ribosomal / Q000032:analysis; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S; C067403:HetR protein, Bacteria