Shewanella polaris sp. nov., a psychrotolerant bacterium isolated from Arctic brown algae

Abstract

A Gram-stain-negative, facultatively anaerobic, flagellated and rod-shaped bacterium, designated strain SM1901^T, was isolated from a brown algal sample collected from Kings Bay, Svalbard, Arctic. Strain SM1901^T grew at -4‒30 °C and with 0-7.0 % (w/v) NaCl. It reduced nitrate to nitrite and hydrolysed DNA and Tween 80. Results of phylogenetic analyses based on 16S rRNA gene sequences indicated that strain SM1901^T was affiliated with the genus <i>Shewanella</i>, showing the highest sequence similarity to the type strain of <i>Shewanella litoralis</i> (97.5%), followed by those of <i>Shewanella vesiculosa</i>, <i>Shewanella livingstonensis</i> and <i>Shewanella saliphila</i> (97.3 % for all three). The major cellular fatty acids were summed feature 3 (C_{16 : 1} <i>ω</i>7<i>с</i> and/or C_{16 : 1} <i>ω</i>6<i>с</i>), C_{16 : 0}, C_{18 : 0}, iso-C_{15 : 0} and C_{17 : 1} <i>ω</i>8<i>с</i> and the major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The respiratory quinones were ubiquinones Q-7, Q-8, menaquinones MK-7(H) and MK-8. The genome of strain SM1901^T was 4648537 nucleotides long and encoded a variety of cold adaptation related genes, providing clues for better understanding the ecological adaptation mechanisms of polar bacteria. The genomic DNA G+C content of strain SM1901^T was 40.5 mol%. Based on the polyphasic evidence presented in this paper, strain SM1901^T was considered to represent a novel species, constituting a novel psychrotolerant lineage out of the known SF clade encompassed by polar <i>Shewanella</i> species, within the genus <i>Shewanella</i>, for which the name <i>Shewanella polaris</i> sp. nov. is proposed. The type strain is SM1901^T (=KCTC 72047^T=MCCC 1K03585^T).