The acetyl-CoA pathway: a newly discovered pathway of autotrophic growth

Wood, Harland G.; Ragsdale, S.W.; Pezacka, E.

doi:10.1016/0968-0004(86)90223-9

Cited by 112 publications

(56 citation statements)

References 42 publications

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“…In acetogenic and methanogenic bacteria, CO is oxidized by multisubunit nickel-containing CO dehydrogenase complexes (8,9,21). The expression of these enzymes is not affected by the presence or absence of CO, and these enzymes appear to be involved in acetate metabolism, with CO oxidation being a secondary reaction (15,29,30).Aerobic carboxydotrophic bacteria oxidize CO by using carbon monoxide oxidase, an oxygen-stable iron-sulfur enzyme containing flavin and molybdopterin (16)(17)(18). In these bacteria CO oxidase is induced by the presence of CO, and hydrogenase is induced in cells grown with CO or with CO2 and H2 (18).…”

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Regulation of carbon monoxide dehydrogenase and hydrogenase in Rhodospirillum rubrum: effects of CO and oxygen on synthesis and activity

et al. 1989

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Exposure of the photosynthetic bacterium Rhodospirillum rubrum to carbon monoxide led to increased carbon monoxide dehydrogenase and hydrogenase activities due to de novo protein synthesis of both enzymes. Two-dimensional gels of [35S]methionine-pulse-labeled cells showed that induction of CO dehydrogenase synthesis was rapidly initiated (<5 min upon exposure to CO) and was inhibited by oxygen. Both CO dehydrogenase and the CO-induced hydrogenase were inactivated by oxygen in vivo and in vitro. In contrast to CO dehydrogenase, the CO-induced hydrogenase was 95% inactivated by heating at 70°C for 5 min. Unlike other hydrogenases, this CO-induced hydrogenase was inhibited only 60% by a 100% CO gas phase.A diverse set of bacteria possess the ability to oxidize CO to CO2 (for reviews, see references 10 through 12, 14, 15, 18, 26, and 30). In acetogenic and methanogenic bacteria, CO is oxidized by multisubunit nickel-containing CO dehydrogenase complexes (8,9,21). The expression of these enzymes is not affected by the presence or absence of CO, and these enzymes appear to be involved in acetate metabolism, with CO oxidation being a secondary reaction (15,29,30).Aerobic carboxydotrophic bacteria oxidize CO by using carbon monoxide oxidase, an oxygen-stable iron-sulfur enzyme containing flavin and molybdopterin (16)(17)(18). In these bacteria CO oxidase is induced by the presence of CO, and hydrogenase is induced in cells grown with CO or with CO2 and H2 (18).Some photosynthetic bacteria tolerate CO (13), and Rhodocyclus (formerly Rhodopseudomonas) gelatinosus has been shown by Uffen and co-workers to utilize CO as its sole carbon and energy source during anaerobic growth in the dark (25). The membrane-bound CO-oxidizing system of R. gelatinosus is inducible by CO and produces CO2 and H2 as products of the oxidation of CO (27,28). CO-dependent evolution of H2 from extracts of Rhodospirillum rubrum S1 has been noted (26). We have previously reported COdependent formation of H2 and CO2 by R. rubrum cells grown in the light on ammonium-malate medium (6) and that exposure of light-grown R. rubrum cultures to CO led to significantly increased levels of CO dehydrogenase (4).In this paper these initial observations are extended to demonstrate that CO induces two enzymatic activities, CO dehydrogenase and a CO-insensitive hydrogenase, which appear to function together to accomplish the oxidation of CO to CO2 and H2. These activities are inactivated by 02 both in vivo and in vitro, and the synthesis of CO dehydrogenase is shown to be inhibited by oxygen. Chromatophore suspensions. Membrane preparations (chromatophores) were derived from cells which had been treated with CO for 24 h before harvest. Cells were broken and the chromatophores were collected by centrifugation as previously described (4) and stored in liquid nitrogen.Enzyme assays. CO dehydrogenase activity was assayed by using a CO-dependent methyl viologen reduction assay as previously described (6). Cells were lysed by grinding before the assay for CO dehydrogenas...

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Regulation of carbon monoxide dehydrogenase and hydrogenase in Rhodospirillum rubrum: effects of CO and oxygen on synthesis and activity

et al. 1989

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“…These CODH enzymes are the key components of metabolic processes that interconvert single carbon units and acetyl coenzyme A, leading ultimately to the generation of acetate or methane or the reduction of sulfate. Aerobic and anaerobic CO oxidation and the fundamental role of CODH in anaerobic pathways of carbon metabolism have been reviewed previously (5,13,20,23,24,29,31,33,34).The oxidation of CO to CO 2 (E 0 Ј ϭ Ϫ0.52 V) coupled to the reduction of protons to H 2 (E 0 Ј ϭ Ϫ0.41 V) under anaerobic conditions has been shown to support the growth of a few organisms and may be a component in the energetics of others. CO-tolerant photosynthetic growth of a bacterium was reported by Hirsch in 1968 (15), and dark CO-dependent growth and H 2 production by Rhodocyclus gelatinosus (formerly Rhodopseudomonas gelatinosa) was established by Uffen and coworkers (4, 6, 30-32).…”

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Carbon monoxide-dependent growth of Rhodospirillum rubrum

1995

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Under dark, anaerobic conditions in the presence of sufficient nickel, Rhodospirillum rubrum grows with a doubling time of under 5 h by coupling the oxidation of CO to the reduction of H ؉ to H 2 . CO-dependent growth of R. rubrum UR294, bearing a kanamycin resistance cassette in cooC, depends on a medium nickel level ninefold higher than that required for optimal growth of coo ؉ strains.Numerous microorganisms oxidize CO to CO 2 : in aerobes the oxidation is catalyzed by an inducible molybdenum-containing oxidase and is coupled to the reduction of oxygen; in strictly anaerobic bacteria and archaea, CO oxidation occurs on a constitutively expressed nickel-containing carbon monoxide dehydrogenase (CODH) and is linked to a variety of reductions. These CODH enzymes are the key components of metabolic processes that interconvert single carbon units and acetyl coenzyme A, leading ultimately to the generation of acetate or methane or the reduction of sulfate. Aerobic and anaerobic CO oxidation and the fundamental role of CODH in anaerobic pathways of carbon metabolism have been reviewed previously (5,13,20,23,24,29,31,33,34).The oxidation of CO to CO 2 (E 0 Ј ϭ Ϫ0.52 V) coupled to the reduction of protons to H 2 (E 0 Ј ϭ Ϫ0.41 V) under anaerobic conditions has been shown to support the growth of a few organisms and may be a component in the energetics of others. CO-tolerant photosynthetic growth of a bacterium was reported by Hirsch in 1968 (15), and dark CO-dependent growth and H 2 production by Rhodocyclus gelatinosus (formerly Rhodopseudomonas gelatinosa) was established by Uffen and coworkers (4, 6, 30-32). Dashekvicz and Uffen also suggested that Rhodospirillum rubrum was capable of slow growth under similar conditions (6, 31). More recently Svetlichny et al. demonstrated the CO-oxidizing and H 2 -generating metabolism and rapid growth of a nonphotosynthetic thermophilic anaerobe, Carboxydothermus hydrogenoformans (27). Methanosarcina barkeri cultures (25) as well as cell suspensions of methanogenic (3, 28), acetogenic (8), and sulfate-reducing (21) organisms also catalyze this reaction with some evidence for coupling to ATP generation (2, 8) and formation of a transmembrane proton gradient (3,8). Hence, CO-dependent H 2 production may be essential to a variety of anaerobic energy generation mechanisms (2,8,13,25,28).Efforts in our laboratories have elaborated the biochemistry and molecular biology of the CO-oxidizing and H 2 -producing system of R. rubrum. Under anaerobic conditions, regardless of the presence of light or other carbon sources, CO induces the synthesis of several proteins, including CODH, an associated Fe-S protein, and a CO-tolerant hydrogenase. The 67-kDa Ni-CODH and the 21-kDa Fe-S protein have been purified and characterized biochemically. In vivo as well as in vitro, electrons derived from CO oxidation, evidently at a Ni-Fe center of CODH (10), are conveyed via the Fe-S protein (and probably other intermediates) to the hydrogenase (11). The genes for these enzymes and additional components h...

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“…Acetogenic bacteria, such as Clostridium thermoautotrophicum, grow heterotrophically on several sugars and autotrophically on H2-CO2, CO, and methanol-CO2 ( (7,12,24).…”

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Carbon monoxide-driven electron transport in Clostridium thermoautotrophicum membranes

1987

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Membrane vesicles of Clostridium thermoautotrophicum prepared by osmotic lysis after lysozyme treatment contained carbon monoxide dehydrogenase and methylenetetrahydrofolate dehydrogenase with specific activities three-to fourfold higher than the specific activity of the cytoplasm. The membrane-associated carbon monoxide dehydrogenase mediated the reduction with CO or the oxidation with CO2 of b-type cytochromes and other electron carriers in the membrane.Acetogenic bacteria, such as Clostridium thermoautotrophicum, grow heterotrophically on several sugars and autotrophically on H2-CO2, CO, and methanol-CO2 (3,23 C. thermoautotrophicum 701/5 was grown in anaerobic medium on glucose (14) under CO2 atmosphere at 59°C at pH 6.5 and harvested during exponential growth (A660, 1.5).Membrane vesicles were prepared by lysozyme treatment by the method of Kaback (11) modified by Otto et al. (16). A lysozyme concentration of 0.8 mg/ml and a temperature of 47°C were used during lysis of the cells. The membranes were washed with 50 mM potassium phosphate buffer (pH 7.0) containing 3 mM dithiothreitol and all metals present in the growth medium (14). The membranes were then stored at 40C in 50 mM potassium phosphate buffer containing 3 mM dithiothreitol and 20% glycerol. Membrane vesicles were made permeable with the addition of 1% toluene. Cell extracts and membranes were also prepared with the French pressure cell as described previously (9). Anaerobic conditions were applied throughout all procedures by using a type B anaerobic chamber (Coy Laboratory Products).H+-ATPase (9), carbon monoxide dehydrogenase (17), hydrogenase (18), formate dehydrogenase (13), methyleneH4folate reductase (2), and formyl-H4folate synthetase (19) were assayed as described previously. Protein was measured by the rose bengal dye-binding assay (5) in the presence of 0.2% Triton X-100 to solubilize the membrane proteins.

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The acetyl-CoA pathway: a newly discovered pathway of autotrophic growth

Cited by 112 publications

References 42 publications

Regulation of carbon monoxide dehydrogenase and hydrogenase in Rhodospirillum rubrum: effects of CO and oxygen on synthesis and activity

Regulation of carbon monoxide dehydrogenase and hydrogenase in Rhodospirillum rubrum: effects of CO and oxygen on synthesis and activity

Carbon monoxide-dependent growth of Rhodospirillum rubrum

Carbon monoxide-driven electron transport in Clostridium thermoautotrophicum membranes

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