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

Five strains representing a novel family within the Gammaproteobacteria were isolated from the estuarine grasses Spartina alterniflora and Juncus 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-G2-2(T). The major menaquinone and ubiquinone were MK-8 (100 %) and Q-8 (93 %), respectively. Predominant fatty acids present were C(12 : 0) aldehyde and/or unknown fatty acid 10.9525 (MIDI designation) and/or iso-C(16 : 1) I/C(14 : 0) 3-OH, C(16 : 1)ω7c/C(16 : 1)ω6c, C(16 : 0), C(17 : 0) cyclo and C(18 : 1)ω7c and/or C(18 : 1)ω6c. 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 order Alteromonadales. All five strains fixed N(2). Analysis of partial nifH gene sequences also revealed a monophyletic lineage within the Gammaproteobacteria, and the sequences were dissimilar to those of any previously described diazotroph. Differences between the novel strains and other members of the Alteromonadales include the inability to produce cytochrome oxidase. The novel strains were metabolically versatile. On the basis of the information described above, the new genus and species Celerinatantimonas diazotrophica gen. nov., sp. nov. are proposed to accommodate the five strains within a new family, Celerinatantimonadaceae fam. nov. The type strain of Celerinatantimonas diazotrophica is S-G2-2(T) ( = ATCC BAA-1368(T)  = DSM 18577(T)).