Physiology and Genomic Characteristics of Strain IMCC13023, a Marine Actinobacterium Isolated from Arctic Seawater

초록

lt has been known that a part of marine actinobactcrial populations are closely related to several freshwater lineages of actinobacteria. However, studies on those marine actinobacteria have been hampered by the lack of relevant isolates. Here we repo11 on the polyphasic taxonomy and genome characteristics ofIMCC13023 that was isolated from Arctic seawater but was closely related to ‘Candidatus Aquiluna rubra’, a freshwater actinobacterial clade, with 97.46% of 16S rRNA gene sequence similarity Optimal growth of strain IMCC13023 was observed at 15 'C, pH 7-8, and in the presence of 1 % NaCl. Some biochemical characteristics, major fatty acids, and polar lipid profiles differentiated the strain fi'om other genεra m the Actinobacteria. Illumina sequencing followed by combinatorial PCR resulted in the complete genome sequence of 1.36 Mb, the smallest genome size ever reported among free-living actinobacteria, with G+C content of 51. 7 mol%. An actinorhodopsin gene was predicted from the genome, suggesting a photoheterotrophic metabolism.