title: Isolation and characterization of a sulfur-oxidizing chemolithotroph growing on crude oil under anaerobic conditions.
abstract: Molecular approaches have shown that a group of bacteria (called cluster 1 bacteria) affiliated with the epsilon subclass of the class Proteobacteria constituted major populations in underground crude-oil storage cavities. In order to unveil their physiology and ecological niche, this study isolated bacterial strains (exemplified by strain YK-1) affiliated with the cluster 1 bacteria from an oil storage cavity at Kuji in Iwate, Japan. 16S rRNA gene sequence analysis indicated that its closest relative was Thiomicrospira denitrificans (90% identity). Growth experiments under anaerobic conditions showed that strain YK-1 was a sulfur-oxidizing obligate chemolithotroph utilizing sulfide, elemental sulfur, thiosulfate, and hydrogen as electron donors and nitrate as an electron acceptor. Oxygen also supported its growth only under microaerobic conditions. Strain YK-1 could not grow on nitrite, and nitrite was the final product of nitrate reduction. Neither sugars, organic acids (including acetate), nor hydrocarbons could serve as carbon and energy sources. A typical stoichiometry of its energy metabolism followed an equation: S(2-) + 4NO(3)(-) --> SO(4)(2-) + 4NO(2)(-) (Delta G(0) = -534 kJ mol(-1)). In a difference from other anaerobic sulfur-oxidizing bacteria, this bacterium was sensitive to NaCl; growth in medium containing more than 1% NaCl was negligible. When YK-1 was grown anaerobically in a sulfur-depleted inorganic medium overlaid with crude oil, sulfate was produced, corresponding to its growth. On the contrary, YK-1 could not utilize crude oil as a carbon source. These results suggest that the cluster 1 bacteria yielded energy for growth in oil storage cavities by oxidizing petroleum sulfur compounds. Based on its physiology, ecological interactions with other members of the groundwater community are discussed.
authors.affiliation: Marine Biotechnology Institute, Kamaishi Laboratories, Heita, Kamaishi City, Iwate 026-0001, Japan.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Kodama
authors.forename: Kazuya
authors.initials: K
authors.lastname: Watanabe
mesh_terms: D000693:Anaerobiosis; D004275:DNA, Ribosomal / Q000032:analysis; D017753:Ecosystem; D020565:Epsilonproteobacteria / Q000145:classification / Q000254:growth & development* / Q000302:isolation & purification*; D005618:Fresh Water / Q000382:microbiology*; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010578:Petroleum; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013455:Sulfur / Q000378:metabolism*; D014876:Water Pollution
chemical_list: D004275:DNA, Ribosomal; D010578:Petroleum; D012336:RNA, Ribosomal, 16S; D013455:Sulfur