Survival Strategy, Metabolic Potential and Taxonomic Reframe of Kocuria polaris

Abstract

Antarctica is renowned as the most inhospitable environment where microorganisms are thriving in the frontiers of life. In the past few years, many novel bacterial species have been reported from the Antarctic environment. During taxonomic re-evaluation of novel bacterial species from Antarctica, it was noticed that Kocuria polaris shared high 16S rRNA gene sequence similarity with Kocuria rosea. In the present study, the taxonomic position, metabolic potentials, and stress survival strategy of K. polaris were evaluated through genome analysis. K. polaris encodes genes for glycolysis, citrate cycle, pentose phosphate pathway, dissimilatory nitrate reduction, assimilatory sulfate reduction, etc. In addition, K. polaris also encodes genes for cold and salt stress. The 16S rRNA gene sequence extracted from K. polaris and K. rosea genomes showed 99.7% similarity. In the phylogenomic tree, K. polaris and K. rosea clustered together. The average nucleotide identity and digital DNA–DNA hybridization values between K. polaris and K. rosea exceeded the threshold (95-96% for ANI and 70% for dDDH) value for distinguishing species, showing that they are similar species. The present study shed light on K. polaris survival strategy in extreme conditions. We further propose to reclassify Kocuria polaris as a later heterotypic synonym of Kocuria rosea.