Vibrio salinus sp. nov., a marine nitrogen-fixing bacterium isolated from the lagoon sediment of an islet inside an atoll in the western Pacific Ocean

A marine, facultatively anaerobic, nitrogen-fixing bacterium, designated strain DNF-1^T, was isolated from the lagoon sediment of Dongsha Island, Taiwan. Cells grown in broth cultures were Gram-negative rods that were motile by means of monotrichous flagella. Cells grown on plate medium produced prosthecae and vesicle-like structures. NaCl was required and optimal growth occurred at about 2–3% NaCl, 25–30 °C and pH 7–8. The strain grew aerobically and was capable of anaerobic growth by fermenting D-glucose or other carbohydrates as substrate. Both the aerobic and anaerobic growth could be achieved with NH₄Cl as a sole nitrogen source. When N₂ served as the sole nitrogen source only anaerobic growth was observed. Major cellular fatty acids were C_14:0, C_16:0 and C_16:1ω7c, while major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The DNA G+C content was 42.2 mol% based on the genomic DNA data. Phylogenetic analyses based on 16S rRNA genes and the housekeeping genes, gapA, pyrH, recA and gyrB, revealed that the strain formed a distinct lineage at species level in the genus Vibrio of the family Vibrionaceae. These results and those from genomic, chemotaxonomic and physiological studies strongly support the assignment of a novel Vibrio species. The name Vibrio salinus sp. nov. is proposed for the novel species, with DNF-1^T (= BCRC 81209^T = JCM 33626^T) as the type strain. This newly proposed species represents the second example of the genus Vibrio that has been demonstrated to be capable of anaerobic growth by fixing N₂ as the sole nitrogen source.