Stenomitos nagquensis sp. nov. (Leptolyngbyaceae, Cyanobacteria) from a Meadow Wetland in the Tibet Plateau: A Novel Species Studied Based on a Polyphasic Approach

Abstract

A novel cyanobacterial strain (CSML-F035) here described as Stenomitos nagquensis sp. nov. was isolated from a plateau meadow wetland habitat in the Tibet Autonomous Region. The novel strain was studied based on a polyphasic approach by combining characteristics of cell morphology and evidence from molecular data and ecology. Phylogenetic analyses based on the 16S rRNA and rbcL genes indicated that the novel strain is a member of the genus Stenomitos (Leptolyngbyaceae) but is positioned in a unique clade, with strongly supported values from BI, ML, and NJ methods. The percentage similarity of the 16S rRNA gene sequence of CSML-F035 compared with known strains of Stenomitos was >97%. Morphologically, S. nagquensis sp. nov. possesses overlapping morphological characteristics with other Stenomitos species, with thin trichomes enclosed in a firm, colorless, hyaline, persistent mucilage. However, the strain appeared to have slightly smaller cells compared to most known species of Stenomitos. Further analyses of the 16S–23S ITS region showed dissimilarity at 11.2–22.8% compared to known species of Stenomitos. The secondary helices—including D1–D1, V2, Box–B, and V3—that were predicted based on the 16S–23S ITS region for Stenomitos nagquensis sp. nov. were also distinct, thereby providing strong additional support for the separation of this species. This study highlights the importance of unexplored habitats in the Tibet region in which cyanobacterial diversity can be deemed high, with many potential new species that remain poorly explored.