Characterization of a Novel Hot-Spring Cyanobacterium Sp. Nov. and Genomic Insights of Molecular Adaptations Into Its Habitat

The newly described genus comprises several strains of filamentous cyanobacteria from diverse, primarily cold, habitats. Here, we sequenced the complete genome of a novel hot-spring strain, sp. PKUAC-SCTA121 (hereafter A121), isolated from Erdaoqiao hot springs (pH 6.32, 40.8°C), China. The analyses of 16S rRNA/16S-23S ITS phylogenies, secondary structures, and morphology strongly support strain A121 as a new species within sp. nov. Notably, strain A121 is the first thermophilic representative of genus and more broadly the first sp. to have its genome sequenced. In addition, results of genome-scale phylogenetic analysis and average nucleotide/amino acid identity as well as DNA-DNA hybridization and patristic analysis verify the establishment of genus previously cryptic to . Comparative genomic analyses reveal that the A121 and A183 from the same hot-spring biome exhibit different genome structures but similar functional classifications of protein-coding genes. Although the core molecular components of photosynthesis, metabolism, and signal transduction were shared by the two strains, distinct genes associated with photosynthesis and signal transduction were identified, indicating that different strategies might be used by these strains to adapt to that specific niche. Furthermore, the complete genome of strain A121 provides the first insight into the genomic features of genus and lays the foundation for future global ecogenomic and geogenomic studies.