Celerinatantimonas diazotrophica gen. nov., sp. nov., a nitrogen-fixing bacterium representing a new family in the Gammaproteobacteria, Celerinatantimonadaceae fam. nov.

Abstract

Five strains representing a novel family within theGammaproteobacteriawere isolated from the estuarine grassesSpartina alternifloraandJuncus roemerianus. All strains were facultatively anaerobic, Gram-negative, short, motile, polar monotrichous rods that were mesophilic, oxidase-negative, catalase-positive, had DNA G+C contents of 41.5–44.4 mol% and required seawater salts or NaCl. Growth was observed at pH 3.5–8.0. Polar lipids diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, aminophospholipid, phospholipids and unidentified aminolipids were found in the representative strain S-G2-2T. The major menaquinone and ubiquinone were MK-8 (100 %) and Q-8 (93 %), respectively. Predominant fatty acids present were C12 : 0aldehyde and/or unknown fatty acid 10.9525 (MIDI designation) and/or iso-C16 : 1I/C14 : 03-OH, C16 : 1ω7c/C16 : 1ω6c, C16 : 0, C17 : 0cyclo and C18 : 1ω7cand/or C18 : 1ω6c. The nearly full-length 16S rRNA gene sequences of the strains were very similar (99–100 % similarity), and the strains were identified as members of the same species by DNA–DNA relatedness measurements. 16S rRNA gene sequence analysis revealed that the strains formed a monophyletic lineage within the orderAlteromonadales. All five strains fixed N2. Analysis of partialnifHgene sequences also revealed a monophyletic lineage within theGammaproteobacteria, and the sequences were dissimilar to those of any previously described diazotroph. Differences between the novel strains and other members of theAlteromonadalesinclude the inability to produce cytochrome oxidase. The novel strains were metabolically versatile. On the basis of the information described above, the new genus and speciesCelerinatantimonas diazotrophicagen. nov., sp. nov. are proposed to accommodate the five strains within a new family,Celerinatantimonadaceaefam. nov. The type strain ofCelerinatantimonas diazotrophicais S-G2-2T( = ATCC BAA-1368T = DSM 18577T).