Digging deeper into the taxonomy of Cylindrospermum and description of Johanseniella tripurensis gen. et sp. nov. from India.

ABSTRACT

The wet soil-inhabiting cyanobacterium URH-6-PS was collected from the state of Tripura, India, and characterized using a polyphasic approach. Initial microscopic analysis indicated the strain to be a member of the genus Cylindrospermum, however, the 16S rRNA gene phylogenetic analysis showed some interesting results. The strain URH-6-PS clustered in the Clade I, which positioned itself outside the Cylindrospermum sensu stricto clade with strong probability/bootstrap support, indicating that the strain may not belong to the genus Cylindrospermum. Further, analysis of the 16S-23S ITS region using the folded secondary structures of the D1-D1', Box-B, and V3 helices and the 16S-23S ITS percentage dissimilarity values clearly indicated the distinctiveness of strain URH-6-PS from other members of the Clade I. The detailed investigations conducted in this study provided sufficient evidence that the taxonomic status of the members of Clade I need to be revised. Interestingly, all members of the clade I originated from tropical and subtropical habitats while members of the Cylindrospermum sensu stricto clade have been reported from temperate conditions. Previous studies had also indicated the possibility of the formation of tropical and subtropical Cylindrospermum-like genera, and thus this comes across as a much-awaited study to resolve the taxonomic complexities around the genus Cylindrospermum. Based on the results obtained in this study and the trends observed in the earlier studies, we describe a novel Cylindrospermum-like genus Johanseniella gen. nov., with the type species Johanseniellatripurensis sp. nov. in accordance with the International Code of Nomenclature for algae, fungi, and plants.