gen. nov., sp. nov., a bacterium isolated from oil sludge, and proposal of fam. nov.

A microaerophilic, Gram-negative, motile, and spiral-shaped bacterium, designated Y-M2, was isolated from oil sludge of Shengli oil field. The optimal growth condition of strain Y-M2 was at 25 °C, pH 7.0, and in the absence of NaCl. The major polar lipid was phosphatidylethanolamine. The main cellular fatty acid was iso-C 3-OH. It contained Q-9 and Q-10 as the predominant quinones. The DNA G+C content was 68.1 mol%. Strain Y-M2 showed the highest 16S rRNA gene sequence similarity to 26-4b (91.1 %). Phylogenetic analyses based on 16S rRNA gene and genomes showed that strain Y-M2 formed a distinct cluster in the order . Genomic analysis showed that Y-M2 possesses a complete nitrogen-fixation cluster which is phylogenetically close to that of methanogene. The cluster, encompassing the nitrogenase genes, was found in every N-fixing strain within the order . Phylogeny, phenotype, chemotaxonomy, and genomic results demonstrated that strain Y-M2 represents a novel species of a novel genus in a novel family fam. nov. in the order , for which the name gen. nov., sp. nov. was proposed. The type strain is Y-M2 (=CCAM 827=JCM 34765).