Phylogenetic insights into the genus Scytonema Bornet et Flahault (Cyanobacteria): A 16S rRNA gene review with the taxonomic assessment of S. schmidtii Gomont

Abstract This study aims to reevaluate the diversity of 16S rRNA gene sequences associated with Scytonema (Nostocales, Cyanobacteria). For that, we first conducted a search for ‘Scytonema’ sequences available in GenBank (NCBI) and aligned the results with reference strains from other Nostocales genera. The alignment totalized 383 OTUs and 800 nucleotide positions analyzed. A FastTree phylogenetic analysis revealed that the ‘Scytonema’ sequences are distributed across 15 distinct clades in addition to the Scytonema sensu stricto clade. These additional clades are positioned among Nostocales genera and phylogenetically distant from the type species, S. hofmanni. Within these clades, we had access to the strain Scytonema sp. CCIBt3568, identified as S. schmidtii, which we believe should be separated from Scytonema, and described as a new genus in the future. Additionally, Bayesian Inference and Maximum Likelihood phylogenies were performed with 97 OTUs and 971 bp, and the polyphyletic status of Scytonema as currently recognized was confirmed.