Polyphasic characterization of a novel hot-spring cyanobacterium gen et sp. nov. and genomic insights into its carbon concentration mechanism.

Thermophilic cyanobacteria play a crucial role as primary producers in hot spring ecosystems, yet their microbiological, taxonomic, and ecological characteristics are not extensively studied. This study aimed to characterize a novel strain of thermophilic cyanobacteria, PKUAC-SCTA174 (A174), using a combination of traditional polyphasic methods and modern genomic-based approaches. The study included 16S rRNA-based phylogeny, ITS secondary structure prediction, morphological and habitat analyses, as well as high-quality genome sequencing with corresponding phylogenomic analyses. The results of the 16S rRNA, 16S-23S ITS secondary structure, morphology, and habitat analyses supported the classification of the strain as a member of a novel genus within the family , closely related to and . Genomic analysis revealed the presence of a sophisticated carbon-concentrating mechanism (CCM) in the strain, involving two CO uptake systems NDH-I, and NDH-I, three types of bicarbonate transporters (BCT1, bicA, sbtA,) and two distinct putative carboxysomal carbonic anhydrases ( and ). The expression of CCM genes was investigated with a CO shift experiment, indicating varying transcript abundance among different carbon uptake systems. Based on the comprehensive characterization, the strain was delineated as , based on the botanical code. The study of the complete genome of strain A174 contributes valuable insights into the genetic characteristics of the genus and related organisms and provides a systematic understanding of thermophilic cyanobacteria. The findings presented here offer valuable data that can be utilized for future research in taxogenomics, ecogenomics, and geogenomics.