Carbon monoxide conversion by thermophilic sulfate-reducing bacteria in pure culture and in co-culture with Carboxydothermus hydrogenoformans

Abstract

Biological sulfate (SO 4 ) reduction with carbon monoxide (CO) as electron donor was investigated. Four thermophilic SO 4 -reducing bacteria, Desulfotomaculum thermoacetoxidans (DSM 5813), Thermodesulfovibrio yellowstonii (ATCC 51303), Desulfotomaculum kuznetsovii (DSM 6115; VKM B-1805), and Desulfotomaculum thermobenzoicum subsp. thermosyntrophicum (DSM 14055), were studied in pure culture and in co-culture with the thermophilic carboxydotrophic bacterium Carboxydothermus hydrogenoformans (DSM 6008). D. thermoacetoxidans and T. yellowstonii were extremely sensitive to CO: their growth on pyruvate was completely inhibited at CO concentrations above 2% in the gas phase. D. kuznetsovii and D. thermobenzoicum subsp. thermosyntrophicum were less sensitive to CO. In pure culture, D. kuznetsovii and D. thermobenzoicum subsp. thermosyntrophicum were able to grow on CO as the only electron donor and, in particular in the presence of hydrogen/carbon dioxide, at CO concentrations as high as 50-70%. The latter SO 4 reducers coupled CO oxidation to SO 4 reduction, but a large part of the CO was converted to acetate. In co-culture with C. hydrogenoformans, D. kuznetsovii and D. thermobenzoicum subsp. thermosyntrophicum could even grow with 100% CO (P CO =120 kPa).

An unconventional pathway for reduction of CO 2 to methane in CO-grown Methanosarcina acetivorans revealed by proteomics

“…A high-sensitivity liquid chromatography͞mass spectrometry analysis, using a hybrid linear ion trap͞Fourier-transform ion cyclotron resonance (LTQ͞FTICR)-MS, was used to identify, quantify, and compare individual proteins from CO-grown cells metabolically labeled with 14 N with separately methanol-grown and acetate-grown cells labeled with 15 N. Abundance ratios of 1,023 proteins were obtained for CO versus methanol grown cells and 846 proteins for CO versus acetate grown cells, corresponding to a total of 1,125 unique proteins (Table 4, which is published as supporting information on the PNAS web site), representing 25% of the 4,524 genes reported in the genome (25). Of these unique proteins, 99 were found to have Ն3-fold differential abundance between CO-and methanol-grown cells and 176 between CO-and acetate-grown cells.…”

“…acetivorans C2A (DSM 804) was grown in high-salt media (50) with one of three growth substrates: (i) 1.0 atm of CO (1 atm ϭ 101.3 kPa), (ii) 100 mM acetate, or (iii) 250 mM methanol. For the methanol and acetate-grown cultures, 14 NH 4 Cl was substituted with 15 NH 4 Cl (98%) (Sigma, St. Louis, MO). Cells were harvested in the midexponential phase of growth at an A 660 of 0.3 (CO-grown), 0.8 (acetate-grown), and 0.6 (methanol-grown) as previously described (28,29).…”

“…54. Each sample was analyzed by liquid chromatographytandem MS by using the Ultimate LC system (Dionex, Sunnyvale, CA) coupled to linear ion trap͞Fourier-transform (LTQ-FT)-MS instrument (Thermo Electron, Waltham, MA), followed by separate sequential Sequest (55) searches for 15 N and 14 N peptides against the National Center for Biotechnology Information's database of M. acetivorans C2A (downloaded June 2005). Peptides with cross correlation values (Xcorr) Ͼ1.5 (1ϩ), 2.0 (2ϩ), and 2.5 (3ϩ) and precursor mass within Ϯ15 ppm of the theoretical mass initially were selected.…”

“…Investigations of aerobic species from the Bacteria domain have contributed important insights into microbial CO oxidation (8,9), as have investigations of anaerobes from the Bacteria domain that conserve energy by coupling CO oxidation to H 2 evolution (10)(11)(12). Further understanding has been derived from studies of CO-using anaerobes from the Bacteria domain that conserve energy by oxidizing CO and reducing CO 2 to acetate (13,14) or reducing sulfate to sulfide (15). Far less is known for pathways of the few CO-using species in the Archaea domain that have been described.…”

H2 enrichment from synthesis gas by Desulfotomaculumcarboxydivorans for potential applications in synthesis gas purification and biodesulfurization

“…Recently, two sulfate reducers, Desulfotomaculum kuznetsovii and Desulfotomaculum thermobenzoicum subsp. thermosynthrophicum were shown capable of CO utilization at CO levels in the gas phase up to 50 kPa (Parshina et al 2005a). The recently isolated Desulfotomaculum carboxydivorans is the first sulfate reducer that shows uninhibited growth on 180 kPa CO at 55°C, both in the presence and absence of sulfate (Parshina et al 2005b).…”