Identification of filamentous cyanobacteria of the indian sundarbans through polyphasic taxonomy

Abstract

The Indian Sundarbans, world's largest tidal mangrove region, comprises of various unique and unpublished biological species. Cyanobacteria were one of those species that can identify according to their characteristics based on morphological, physiological, and genetic taxon studies. They were collected and maintained in an axenic culture under suitable condition in the laboratory. The cyanobacterial species were isolated and purified for polyphasic taxonomical studies. The two distinctive purified strains were named as S9 and S15. The morphological study of S9 strain and S15 strain revealed the similarities with simple filament structure, predominantly constricted cell wall, and presence of mucilaginous sheath. The ultrastructural study revealed the presence of homologous thylakoid arrangement in each strain as compared to their respective families. The physiological study revealed the amount of chlorophyll a content, carotenoid content, and phycobiliprotein content among the two distinctive strains. The S9 strain and S15 strain were subjected to the identification through a polyphasic taxonomic study. The 16S rRNA gene sequencing revealed the similarity values with their reference strains and assumes to be assigned as a novel taxon by consensus value of phylogenetic tree with high bootstrap values. The representation of the phylogenetic tree topology of S9 strain and S15 strain showed the closest relation and well-supported clade with the reference strain Euryhalinema mangrovii AP9F belongs to the Nodosilineaceae family. The secondary structure of the 16S-23S ITS region of S9 strain and S15 strain revealed the dissimilarities values with their respective strains in terms of basal sequence length as well as terminal loop and bulges. The overall analytic investigation leads to the S9 strain and S15 strain to be considered as two species under a novel genus