Genomic Insights into Marinovum sedimenti sp. nov., Isolated from Okhotsk Sea Bottom Sediments, Suggest Plasmid-Mediated Strain-Specific Motility

Two Gram-negative aerobic halophilic bacteria, designated KMM 9989^T and KMM 9879, were isolated from a bottom sediment sample of the Okhotsk Sea, Russia. The novel strains grew in 0.5-4% NaCl, at 5-35 °C and pH 5.5-10.0. Phylogenetic analyses based on 16S rRNA gene and whole genome sequences placed strains KMM 9989^T and KMM 9879 within the family <i>Roseobacteraceae</i>, where they were clustered with their closest relative <i>Marinovum algicola</i> KCTC 22095^T. The average nucleotide identity (ANI) between strain KMM 9989^T and <i>Marinovum algicola</i> KCTC 22095^T was 81.4%. The level of digital DNA-DNA hybridization (dDDH) between the novel isolates KMM 9989^T and KMM 9879 was 97%, while between strain KMM 9989^T and <i>Marinovum algicola</i> KCTC 22095^T, it was 27%. Strains KMM 9989^T and KMM 9879 contained Q-10 as the predominant ubiquinone and C_18:1<i>ω7c</i> as the major fatty acid. The polar lipids were phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, an unidentified aminolipid, two unidentified phospholipids, and three unidentified lipids. The genomic size of strains KMM 9989^T and KMM 9879 was determined to be 4,040,543 bp and 3,969,839 bp with a DNA GC content of 61.3 and 61.4 mol%, respectively. Both strains contained a common plasmid of 238,277 bp and a strain-specific plasmid (188,734 bp for KMM 9989^T and 118,029 bp for KMM 9879). It is suggested that the motility of KMM 9879 may be mediated by the presence of a complete <i>fla2</i>-type operon in the strain-specific chromid. Thus, based on the phylogenetic analyses and distinctive phenotypic characteristics, the novel marine strains KMM 9989^T and KMM 9879 are proposed to be classified as a novel species <i>Marinovum sedimenti</i> sp. nov. with the strain KMM 9989^T (=KCTC 8835^T) as the type strain of the species.