Geosporobacter ferrireducens sp. nov., an anaerobic iron-reducing bacterium isolated from an oil-contaminated site.

In this study, an alkaliphilic and heterotrophic iron-reducing bacterial strain, IRF9(T), was isolated from an oil-contaminated soil in the Republic of Korea. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain IRF9(T) belongs to the genus Geosporobacter in the family Clostridiaceae and is most closely related to Geosporobacter subterraneus VNs68(T) (96.9 % sequence similarity). Cells of strain IRF9(T) were observed to be straight or curved rod-shaped, motile and Gram-negative. Optimal growth of strain IRF9(T) was observed at pH 9.0-9.5 and 40 °C. The strain was found to grow within pH and temperature ranges of 6.5-10.0 and 25-45 °C, respectively. NaCl was not required for growth. Fe(III), but not sulfate, thiosulfate or elemental sulfur can be used by strain IRF9(T) as an electron acceptor. A limited number of carbohydrates and amino acids, including D-glucose, D-fructose, D-mannitol, D-ribose and L-arginine, support growth of strain IRF9(T). The main fatty acids (>10 %) of strain IRF9(T) were identified as C14:0 (18.4 %), C16:1 cis9 (13.6 %), C16:0 (12.4 %) and C16:0 dimethyl acetal (17.7 %). Major respiratory quinone was identified as menaquinone MK-5 (V-H2). The main polar lipids were found to be phosphatidylethanolamine, diphosphatidylglycerol and phosphatidylglycerol. The DNA G+C content of strain IRF9(T) was determined to be 37.2 mol%, which is lower than that of G. subterraneus VNs68(T) (42.2 mol%). Based on phenotypic, chemotaxonomic, and phylogenetic studies, we conclude that strain IRF9(T) (=JCM 19987(T) = KCTC 15395(T)) represents a new species of the genus Geosporobacter, for which we propose the name Geosporobacter ferrireducens sp. nov.