Genomic Characteristics of Strain IMCC26207, a Non-colony-forming Actinobacterium, Isolated from an Oligotrophic Freshwater Lake

초록

Although the phylum Actinobacteria is a common and numerically important component in freshwater habitats, their potential roles in biogeochemical process remain unknown due to the scarcity of reference genomic resources. We report here the draft genome sequence of strain IMCC26207, a noncolony forming freshwater actinobacterium, with the description of the genome properties. Strain IMCC26207 was isolated from the surface layer of Lake Soyang by the dilution-to-extinction culturing method. Phylogenetic analysis of 16S rRNA gene sequences indicated that strain IMCC26207 formed a distinct lineage in the order Acidimicrobiales of the phylum Actinobacteria. The closest relative among previously identified bacteria was ‘Candidatus Microthrix parvicella’ (16S rRNA similarity: 91.7%). The draft genome consisted of 10 contigs with a total size of 3.3 Mb and an average G+C content of 57.3%. The IMCC26207 genome was predicted to contain 2,975 protein-coding genes and 51 RNA genes, including 45 tRNA genes. Approximately 76% of the protein coding genes could be assigned with a specific function. Annotation of the IMCC26207 genome showed several traits of adaptation to living in oligotrophic freshwater environments. Comparative analysis revealed that the IMCC26207 genome was distinct from ‘Candidatus Microthrix’ genomes; therefore, we propose the name ‘Candidatus Limnosphaera aquatica’ for this bacterium. [Supported by a grant of the Mid-Career Research Program through the NRF]