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

Abstract

In this study, an alkaliphilic and heterotrophic iron-reducing bacterial strain, IRF9T, was isolated from an oil-contaminated soil in the Republic of Korea. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain IRF9T belongs to the genus Geosporobacter in the family Clostridiaceae and is most closely related to Geosporobacter subterraneus VNs68T (96.9 % sequence similarity). Cells of strain IRF9T were observed to be straight or curved rod-shaped, motile and Gram-negative. Optimal growth of strain IRF9T 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 IRF9T 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 IRF9T. The main fatty acids (>10 %) of strain IRF9T 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 IRF9T was determined to be 37.2 mol%, which is lower than that of G. subterraneus VNs68T (42.2 mol%). Based on phenotypic, chemotaxonomic, and phylogenetic studies, we conclude that strain IRF9T (=JCM 19987T = KCTC 15395T) represents a new species of the genus Geosporobacter, for which we propose the name Geosporobacter ferrireducens sp. nov.