<i>Oxynema</i> <i>mangrovii</i> sp. nov., a new filamentous species (Oscillatoriales, Cyanobacteria) from Atlantic forest mangrove

A cyanobacterial strain isolated from Brazilian mangrove soil and classified as a member of the genus <i>Phormidium</i> was afterward affiliated to the genus <i>Oxynema</i>. To define the species of this <i>Oxynema</i> strain CENA135, we sequenced its whole genome and applied a polyphasic taxonomic approach. This strain, with all the morphological features recognized for the <i>Oxynema</i> genus, had its genome assembled in 11 scaffolds with a total size of 6,235,022 bp, a G + C content of 51.6%, 4,720 protein-coding genes, and five 16S rRNA genes. Genes related to ecological resistance were annotated, demonstrating the relevance of obtaining high-quality genome assemblies from underrepresented habitats. A phylogenomic tree inferred by GTDB-Tk based on the alignment of 120 conserved proteins clustered <i>Oxynema</i> sp. CENA135 together with the strain <i>Oxynema aestuarii</i> AP17 isolated from Indian mangrove soil, and digital DNA-DNA hybridization and average nucleotide identity values between these two strains were 92.8 and 95.78%, respectively. Phylogenetic analysis based on 16S rRNA gene sequences placed the strain CENA135 in a separate and well-supported major clade (100% bootstrap) containing <i>Oxynema</i> species, and its 16S rRNA gene sequence showed identity ≤98.6% compared to the other species of the genus. Moreover, the strain CENA135 had a distinct 16S-23S ITS sequence and secondary structure polymorphisms in comparison to the other <i>Oxynema</i> species, supporting its recognition as a novel species. On the basis of evidence from this polyphasic study, strain CENA135 should be designated as representing a novel species of the genus <i>Oxynema</i>, for which the name <i>Oxynema mangrovii</i> sp. nov. is proposed under the provisions of the International Code of Nomenclature for algae, fungi, and plants.