Neptunomonas antarctica sp. nov., isolated from marine sediment.

A Gram-negative, motile, oxidase- and catalase-positive and facultatively aerobic bacterium, designated S3-22T, was isolated from marine sediment of the Nella Fjord, Antarctica. Strain S3-22T reduced nitrate to nitrite and grew at pH 6.0-8.0, at 4-25 degrees C and with 0.5-5% (w/v) NaCl. It contained Q-8 as the only respiratory quinone and summed feature 3 (C16:1omega7c and/or iso-C15:0 2-OH), C16:0 and C18:1omega7c as the major cellular fatty acids. The genomic DNA G+C content was 45.6 mol%. Phylogenetic analyses of 16S rRNA gene sequences showed that strain S3-22T was affiliated with the genus Neptunomonas, with 97.1% sequence similarity to Neptunomonas japonica JAMM 0745T and 94.8% to Neptunomonas naphthovorans NAG-2N-126T, the type strains of the only two recognized Neptunomonas species. DNA-DNA relatedness between strain S3-22T and N. japonica JCM 14595T was 20.4%. Strain S3-22T could be distinguished from the type strains of Neptunomonas species by several phenotypic properties. Based on the evidence from our polyphasic study, strain S3-22T represents a novel Neptunomonas species, for which the name Neptunomonas antarctica sp. nov. is proposed. The type strain is S3-22T (=CCTCC AB 209086T =KACC 14056T).