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 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 ؊ 3 SO 4 2؊ ؉ 4NO 2 ؊ (⌬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.

Bacteria associated with iron seeps in a sulfur-rich, neutral pH, freshwater ecosystem

“…Clone 212 could be assigned to the family Incertae cedis 5, but not to the genus Leptothrix, although it had 95% sequence identity to L. discophora strain-1 (L33975; Siering and Ghiorse, 1996). Clone 181 could be assigned to the epsilonproteobacterial, sulfur-oxidizing and nitrate-reducing genus Sulfuricurvum, and had a 96% sequence identity to Sulfuricurvum kuijense strains YK-2 and YK-4 (Kodama and Watanabe, 2003).…”

Hydrocarbon biodegradation by Arctic sea-ice and sub-ice microbial communities during microcosm experiments, Northwest Passage (Nunavut, Canada)

“…7B). Several genera of this class that are able to oxidize sulfur compounds dominated the microbial biomass in groundwater contaminated by crude-oil extraction activities (Kodama & Watanabe 2003;Hubert et al 2011). This may explain why dibenzothiophene, a sulfur-containing compound, and its methylated forms were highly oxidized (average of 97% loss) in sub-ice waters but not in sea ice (< 40% loss; Fig.…”

Dysgonomonas oryzarvi sp. nov., isolated from a microbial fuel cell

“…The medium (10 ml) was infused into a test tube (18 mm in diameter6180 mm) under reduced copper-treated N 2 gas, and the test tube was sealed with a butyl-rubber stopper and capped with a screw cap (Sanshin Kogyo). Growth was monitored by measuring optical density at 660 nm (OD 660 ) using a miniphoto 518R (Taitec), and cell concentration was determined by direct counting of 4',6-diamidino-2-phenylindole stained cells under an epifluorescence microscope (Kodama & Watanabe, 2003). Bacterial cells were stored at 280 u C in the modified 1/10 PYGV medium supplemented with 15 % (v/v) glycerol.…”