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Papers by James Champine

Rhodocyclus gelatinosus grows anaerobically at the expense of carbon monoxide (CO). The CO-oxidat... more Rhodocyclus gelatinosus grows anaerobically at the expense of carbon monoxide (CO). The CO-oxidation system was substrate-induced and i CO/light, cells grew at an exponential rate with ever increasing amounts of CO:MV oxidoreduc-tase activity (the measure of CO oxidation). Once strain 1 reached a high cell density, the concentra-tion of CO became limiting and gas oxidation activity suddenly decreased. Cell growth con-tinued unaffected. To help explain this, it ap-peared that strain 1 variably used both CO oxida-tion and photometabolism to support growth in CO/light. Light intensity determined the upper limit of amounts of CO:MV oxidoreductase in a culture, while intermediate amounts were regu-lated by CO concentration. Thus, in darkness, cells produced the maximum CO oxidation activ-ity, whereas in growth-saturating li ht, the mini-mum limit occurred. The lower the levels of CO:MV oxidoreductase in cells, the greater the

Applied and Environmental Microbiology, 1997

The transformation of 1,2-dichloropropane (1,2-D) was observed in anaerobic microcosms and enrich... more The transformation of 1,2-dichloropropane (1,2-D) was observed in anaerobic microcosms and enrichment cultures derived from Red Cedar Creek sediment. 1-Chloropropane (1-CP) and 2-CP were detected after an incubation period of 4 weeks. After 4 months the initial amount of 1,2-D was stoichiometrically converted to propene, which was not further transformed. Dechlorination of 1,2-D was not inhibited by 2-bromoethanesulfonate. Sequential 5% (vol/vol) transfers from active microcosms yielded a sediment-free, nonmethanogenic culture, which completely dechlorinated 1,2-D to propene at a rate of 5 nmol min(sup-1) mg of protein(sup-1). No intermediate formation of 1-CP or 2-CP was detected in the sediment-free enrichment culture. A variety of electron donors, including hydrogen, supported reductive dechlorination of 1,2-D. The highest dechlorination rates were observed between 20(deg) and 25(deg)C. In the presence of 1,2-D, the hydrogen threshold concentration was below 1 ppm by volume (ppmv...

Journal of Bacteriology, 1987

Rhodocyclus gelatinosus 1 grows anaerobically in the dark at the expense of carbon monoxide. Topo... more Rhodocyclus gelatinosus 1 grows anaerobically in the dark at the expense of carbon monoxide. Topographical studies with methyl viologen as the membrane probe indicated that CO oxidation and H2 production sites were on the cytoplasmic side of the cell membrane. Membrane-associated hydrogen gas production appeared to be a unidirectional reaction. In the dark, strain 1 whole cells oxidized CO and incorporated about 306 pmol of 32Pi into ATP per min per mg of protein. With CO as the sole energy-yielding substrate, cells grew with a low growth yield coefficient of 3.7 g (dry weight) of cells per mg of CO oxidized.

Anaerobe, 2000

To investigate electron transport in the dissimilatory iron-reducing isolate Geobacter metallired... more To investigate electron transport in the dissimilatory iron-reducing isolate Geobacter metallireducens strain GS-15, assays for redox enzymes and characterizations of cytochromes were performed. G. metallireducens produced 1.56 g dry cell weight per mol e 7 transferred when grown on benzoate and contained the following citric acid cycle enzymes (activities in nkat per mg cell protein); isocitrate dehydrogenase (0.84), coenzyme A-dependent 2oxoglutarate: methyl viologen oxidoreductase (2.80), succinate dehydrogenase (0.80), and malate dehydrogenase (8.35). An oxygen-sensitive, soluble coenzyme A-dependent 2-oxoglutarate: ferredoxin oxidoreductase (0.14) with no NAD(P)-activity was observed. In cell suspensions NADPH, but not NADH, could reduce methyl viologen (2.45). Isocitrate and malate dehydrogenase activities were soluble enzymes that coupled with NADP and NAD, respectively. NADPH (0.94) and NADH (1.85) oxidation activities were observed in detergent solubilized, whole-cell suspensions using the artificial electron acceptor menadione. Menaquinone was observed at 1.2 mmol per g cell protein. The triheme c 7 cytochrome was purified and 37 amino acids were determined. The mass observed by mass spectroscopy was 9684+10 Da. The average mid-point potential for the three hemes was measured at 791 mV. The growth yield, redox reactions, and electron transfer components are discussed with regards to possible sites of energy conservation during growth on iron(III).

Archives of Microbiology, 1993

The gram-negative metal-reducing microorganism, previously known as strain GS-15, was further cha... more The gram-negative metal-reducing microorganism, previously known as strain GS-15, was further characterized. This strict anaerobe oxidizes several short-chain fatty acids, alcohols, and monoaromatic compounds with Fe(III) as the sole electron acceptor. Furthermore, acetate is also oxidized with the reduction of Mn(IV), U(VI), and nitrate. In whole cell suspensions, the c-type cytochrome(s) of this organism was oxidized by physiological electron acceptors and also by gold, silver, mercury, and chromate. Menaquinone was recovered in concentrations comparable to those previously found in gram-negative sulfate reducers. Profiles of the phospholipid ester-linked fatty acids indicated that both the anaerobic desaturase and the branched pathways for fatty acid biosynthesis were operative. The organism contained three lipopolysaccharide hydroxy fatty acids which have not been previously reported in microorganisms, but have been observed in anaerobic freshwater sediments. The 16S rRNA sequence indicated that this organism belongs in the delta proteobacteria. Its closest known relative is Desulfuromonas acetoxidans. The name Geobacter metallireducens is proposed.

FEMS Microbiology Letters, 1987

Rhodocyclus gelatinosus grows anaerobically at the expense of carbon monoxide (CO). The COoxidati... more Rhodocyclus gelatinosus grows anaerobically at the expense of carbon monoxide (CO). The COoxidation system was substrate-induced and in CO/light, cells grew at an exponential rate with ever increasing amounts of CO:MV oxidoreductase activity (the measure of CO oxidation). Once strain 1 reached a high cell density, the concentration of CO became limiting and gas oxidation activity suddenly decreased. Cell growth continued unaffected. To help explain this, it appeared that strain 1 variably used both CO oxidation and photometabolism to support growth in CO/light. Light intensity determined the upper limit of amounts of CO:MV oxidoreductase in a culture, while intermediate amounts were regulated by CO concentration. Thus, in darkness, cells produced the maximum CO oxidation activity, whereas in growth-saturating light, the minimum limit occurred. The lower the levels of CO:MV oxidoreductase in cells, the greater the

Rhodocyclus gelatinosus grows anaerobically at the expense of carbon monoxide (CO). The CO-oxidat... more Rhodocyclus gelatinosus grows anaerobically at the expense of carbon monoxide (CO). The CO-oxidation system was substrate-induced and i CO/light, cells grew at an exponential rate with ever increasing amounts of CO:MV oxidoreduc-tase activity (the measure of CO oxidation). Once strain 1 reached a high cell density, the concentra-tion of CO became limiting and gas oxidation activity suddenly decreased. Cell growth con-tinued unaffected. To help explain this, it ap-peared that strain 1 variably used both CO oxida-tion and photometabolism to support growth in CO/light. Light intensity determined the upper limit of amounts of CO:MV oxidoreductase in a culture, while intermediate amounts were regu-lated by CO concentration. Thus, in darkness, cells produced the maximum CO oxidation activ-ity, whereas in growth-saturating li ht, the mini-mum limit occurred. The lower the levels of CO:MV oxidoreductase in cells, the greater the

Applied and Environmental Microbiology, 1997

The transformation of 1,2-dichloropropane (1,2-D) was observed in anaerobic microcosms and enrich... more The transformation of 1,2-dichloropropane (1,2-D) was observed in anaerobic microcosms and enrichment cultures derived from Red Cedar Creek sediment. 1-Chloropropane (1-CP) and 2-CP were detected after an incubation period of 4 weeks. After 4 months the initial amount of 1,2-D was stoichiometrically converted to propene, which was not further transformed. Dechlorination of 1,2-D was not inhibited by 2-bromoethanesulfonate. Sequential 5% (vol/vol) transfers from active microcosms yielded a sediment-free, nonmethanogenic culture, which completely dechlorinated 1,2-D to propene at a rate of 5 nmol min(sup-1) mg of protein(sup-1). No intermediate formation of 1-CP or 2-CP was detected in the sediment-free enrichment culture. A variety of electron donors, including hydrogen, supported reductive dechlorination of 1,2-D. The highest dechlorination rates were observed between 20(deg) and 25(deg)C. In the presence of 1,2-D, the hydrogen threshold concentration was below 1 ppm by volume (ppmv...

Journal of Bacteriology, 1987

Rhodocyclus gelatinosus 1 grows anaerobically in the dark at the expense of carbon monoxide. Topo... more Rhodocyclus gelatinosus 1 grows anaerobically in the dark at the expense of carbon monoxide. Topographical studies with methyl viologen as the membrane probe indicated that CO oxidation and H2 production sites were on the cytoplasmic side of the cell membrane. Membrane-associated hydrogen gas production appeared to be a unidirectional reaction. In the dark, strain 1 whole cells oxidized CO and incorporated about 306 pmol of 32Pi into ATP per min per mg of protein. With CO as the sole energy-yielding substrate, cells grew with a low growth yield coefficient of 3.7 g (dry weight) of cells per mg of CO oxidized.

Anaerobe, 2000

To investigate electron transport in the dissimilatory iron-reducing isolate Geobacter metallired... more To investigate electron transport in the dissimilatory iron-reducing isolate Geobacter metallireducens strain GS-15, assays for redox enzymes and characterizations of cytochromes were performed. G. metallireducens produced 1.56 g dry cell weight per mol e 7 transferred when grown on benzoate and contained the following citric acid cycle enzymes (activities in nkat per mg cell protein); isocitrate dehydrogenase (0.84), coenzyme A-dependent 2oxoglutarate: methyl viologen oxidoreductase (2.80), succinate dehydrogenase (0.80), and malate dehydrogenase (8.35). An oxygen-sensitive, soluble coenzyme A-dependent 2-oxoglutarate: ferredoxin oxidoreductase (0.14) with no NAD(P)-activity was observed. In cell suspensions NADPH, but not NADH, could reduce methyl viologen (2.45). Isocitrate and malate dehydrogenase activities were soluble enzymes that coupled with NADP and NAD, respectively. NADPH (0.94) and NADH (1.85) oxidation activities were observed in detergent solubilized, whole-cell suspensions using the artificial electron acceptor menadione. Menaquinone was observed at 1.2 mmol per g cell protein. The triheme c 7 cytochrome was purified and 37 amino acids were determined. The mass observed by mass spectroscopy was 9684+10 Da. The average mid-point potential for the three hemes was measured at 791 mV. The growth yield, redox reactions, and electron transfer components are discussed with regards to possible sites of energy conservation during growth on iron(III).

Archives of Microbiology, 1993

The gram-negative metal-reducing microorganism, previously known as strain GS-15, was further cha... more The gram-negative metal-reducing microorganism, previously known as strain GS-15, was further characterized. This strict anaerobe oxidizes several short-chain fatty acids, alcohols, and monoaromatic compounds with Fe(III) as the sole electron acceptor. Furthermore, acetate is also oxidized with the reduction of Mn(IV), U(VI), and nitrate. In whole cell suspensions, the c-type cytochrome(s) of this organism was oxidized by physiological electron acceptors and also by gold, silver, mercury, and chromate. Menaquinone was recovered in concentrations comparable to those previously found in gram-negative sulfate reducers. Profiles of the phospholipid ester-linked fatty acids indicated that both the anaerobic desaturase and the branched pathways for fatty acid biosynthesis were operative. The organism contained three lipopolysaccharide hydroxy fatty acids which have not been previously reported in microorganisms, but have been observed in anaerobic freshwater sediments. The 16S rRNA sequence indicated that this organism belongs in the delta proteobacteria. Its closest known relative is Desulfuromonas acetoxidans. The name Geobacter metallireducens is proposed.

FEMS Microbiology Letters, 1987

Rhodocyclus gelatinosus grows anaerobically at the expense of carbon monoxide (CO). The COoxidati... more Rhodocyclus gelatinosus grows anaerobically at the expense of carbon monoxide (CO). The COoxidation system was substrate-induced and in CO/light, cells grew at an exponential rate with ever increasing amounts of CO:MV oxidoreductase activity (the measure of CO oxidation). Once strain 1 reached a high cell density, the concentration of CO became limiting and gas oxidation activity suddenly decreased. Cell growth continued unaffected. To help explain this, it appeared that strain 1 variably used both CO oxidation and photometabolism to support growth in CO/light. Light intensity determined the upper limit of amounts of CO:MV oxidoreductase in a culture, while intermediate amounts were regulated by CO concentration. Thus, in darkness, cells produced the maximum CO oxidation activity, whereas in growth-saturating light, the minimum limit occurred. The lower the levels of CO:MV oxidoreductase in cells, the greater the