Description of a novel filamentous cyanobacterial species of Leptodesmis (Leptolyngbyaceae, Cyanobacteria) in China based on the polyphasic approach

The middle route of the South-to-North Water Diversion Project supplies high-quality water to various water treatment plants along its path and increases the diversity of cyanobacteria present in the raw water. A filamentous cyanobacterium Leptodesmis xinxiangensis HNU2023 was successfully isolated from a drinking water plant in Xinxiang, which receives its water supply from this middle route. Morphologically, this strain exhibits similarities to cyanobacterial taxa within the genera Leptodesmis and Phormidesmis. Phylogenetic analysis, based on 16S rRNA gene sequences, indicates that this strain is closely related to Leptodesmis, forming a well-supported clade. The 16S rRNA gene sequences of the strain show between 95.5% and 98% similarity to known Leptodesmis species, suggesting that it represents a new species within this genus. Moreover, the distinctive patterns observed in the D1-D1′ and Box-B helix regions of the 16S–23S rRNA internal transcribed spacer (ITS) secondary structure further confirm that this strain is a novel species. Consequently, the comprehensive analysis of the isolated strain, in conjunction with morphological characteristics, 16S rRNA gene sequencing, and ITS secondary structure, substantiates the classification of Leptodesmis xinxiangensis sp. nov. as a new species within the genus Leptodesmis.