Nitrate as a preferred electron sink for the acetogen Clostridium thermoaceticum

Seifritz, Corinna; Daniel, Steven L.; Gößner, Anita S.; Drake, Harold L.

doi:10.1128/jb.175.24.8008-8013.1993

Cited by 86 publications

(73 citation statements)

References 25 publications

(24 reference statements)

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“…Nitrate, rather than CO,, is the preferred terminal electron acceptor for Clostridium thermoaceticum and C. thermoautotrophicum and inhibits the ability of these acetogens to form acetate by repressing the electron transport system normally engaged in the acetyl coenzyme A (acetyl-CoA) pathway (21,26,57). When strain DG-lT was grown in the presence of nitrate, nitrate was not appreciably utilized and acetate production was not appreciably affected, indicating that nitrate was not used as an alternative electron acceptor by DG-lT. Sulfate was also not used as an alternative electron acceptor.…”

Section: Resultsmentioning

confidence: 99%

Sporomusa silvacetica sp. nov., an Acetogenic Bacterium Isolated from Aggregated Forest Soil

Kuhner

Frank

Griesshammer

et al. 1997

International Journal of Systematic Bacteriology

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Sporomusa silvacetica sp. nov. DG-lT (= DSMZ 10669T) (T = type strain) was isolated from well-drained, aggregated forest soil (pH 6.0) in east-central Germany. The cells were obligately anaerobic, slightly curved rods and were motile by means of laterally inserted flagella on the concave side of each cell. Typical cells were approximately 3.5 by 0.7 pm. Cells stained weakly gram positive, but thin sections revealed a complex multilayer cell wall. Spores were spherical and distended the sporangia. Growth and substrate utilization occurred with ferulate, vanillate, fructose, betaine, fumarate, 2,3-butanediol, pyruvate, lactate, glycerol, ethanol, methanol, formate, and H,-CO,. With most substrates, acetate was the primary reduced end product and was produced in stoichiometries indicative of an acetyl-coenzyme A pathway-dependent metabolism. Fumarate was dismutated to succinate and acetate. Methoxyl and acrylate groups of various aromatic compounds were 0-demethylated and reduced, respectively. Yeast extract was not required for growth. Cells grew optimally at approximately 30°C and pH 6.8; under these conditions and with fructose as the substrate, the doubling time was approximately 14 h. The lowest temperature that supported growth was between 5 and 10°C. The carbon monoxide dehydrogenase and hydrogenase activities were approximately 9 and 102 pmol min-' mg of protein-', respectively. A type b cytochrome was detected in the membrane. The G+C content was approximately 43 mol%. Phylogenetic analysis of the 16s ribosomal DNA indicated that DG-lT was most closely related to members of the genus Sporomusa in the Clostridium subphylum of the gram-positive bacteria.Low-molecular-weight aliphatic organic acids are present in mineral forest soil solutions and are believed to play roles in soil formation, solubility of toxic metals, and plant growth (23,24,30,49,58,59). In this regard, acetate is a dominate organic acid detected in mineral soils (59), and it has been proposed that the acetate in mineral soils is produced primarily through the collective action of facultatively and obligately anaerobic microorganisms (35,63). Although well-drained soils are not considered typical acetogenic habitats, supplementation of forest (34, 35), prairie (63), and tundra (46) soils with H, or CO results in the utilization of substrates and the production of acetate in stoichiometries approximating those expected for H,-or CO-dependent acetogenesis. In addition, acetogenic consortia are readily enriched from mineral forest soils (35,48) and leaf litter (36). To further evaluate the occurrence of acetogens in well-drained, aggregated soils, an acetogen was isolated from a beech forest in east-central Germany. The collective characteristics of this isolate (strain DG-lT [T = type strain]) are not consistent with the characteristics of any previously described acetogenic bacterium, and it is proposed that this organism should be placed in a new species, Sporomusa silvacetica. MATERIALS AND METHODSSoil collection. Forest soil (a silty loam...

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Section: Resultsmentioning

confidence: 99%

Sporomusa silvacetica sp. nov., an Acetogenic Bacterium Isolated from Aggregated Forest Soil

Kuhner

Frank

Griesshammer

et al. 1997

International Journal of Systematic Bacteriology

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“…Acetogens can use not only CO 2 but also alternative electron acceptors, including arylacrylates (2,53), fumarate (11,12,35), dimethyl sulfoxide (3), and nitrate (17,50). Acetobacterium woodii is known to reduce the carbon-carbon double bond of phenylacrylates, such as caffeate, as shown in Fig.…”

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Dissection of the Caffeate Respiratory Chain in the Acetogen Acetobacterium woodii : Identification of an Rnf-Type NADH Dehydrogenase as a Potential Coupling Site

et al. 2007

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The anaerobic acetogenic bacterium Acetobacterium woodii couples caffeate reduction with electrons derived from hydrogen to the synthesis of ATP by a chemiosmotic mechanism with sodium ions as coupling ions, a process referred to as caffeate respiration. We addressed the nature of the hitherto unknown enzymatic activities involved in this process and their cellular localization. Cell extract of A. woodii catalyzes H 2 -dependent caffeate reduction. This reaction is strictly ATP dependent but can be activated also by acetyl coenzyme A (CoA), indicating that there is formation of caffeyl-CoA prior to reduction. Two-dimensional gel electrophoresis revealed proteins present only in caffeate-grown cells. Two proteins were identified by electrospray ionization-mass spectrometry/mass spectrometry, and the encoding genes were cloned. These proteins are very similar to subunits ␣ (EtfA) and ␤ (EtfB) of electron transfer flavoproteins present in various anaerobic bacteria. Western blot analysis demonstrated that they are induced by caffeate and localized in the cytoplasm. Etf proteins are known electron carriers that shuttle electrons from NADH to different acceptors. Indeed, NADH was used as an electron donor for cytosolic caffeate reduction. Since the hydrogenase was soluble and used ferredoxin as an electron acceptor, the missing link was a ferredoxin:NAD ؉ oxidoreductase. This activity could be determined and, interestingly, was membrane bound. A search for genes that could encode this activity revealed DNA fragments encoding subunits C and D of a membrane-bound Rnf-type NADH dehydrogenase that is a potential Na ؉ pump. These data suggest the following electron transport chain: H 2 3 ferredoxin 3 NAD ؉ 3 Etf 3 caffeyl-CoA reductase. They also imply that the sodium motive step in the chain is the ferredoxin-dependent NAD ؉ reduction catalyzed by Rnf.

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“…The reduction of CO 2 to acetate is coupled to respiratory conservation of energy via either membranous electron transport or sodium pumping systems (11,27,33). Although supplemental CO 2 can be essential or greatly stimulatory to acetogenesis under certain conditions, acetogens can use other respiratory reductant sinks (15,17,18), including aromatic acrylate groups (2,22,32,40), fumarate (13, 31), dimethyl sulfoxide (3), and nitrate (20,37).In contrast to the numerous studies that have evaluated the respiratory capacities of acetogens, the fermentation capacities of this bacteriological group have been minimally examined. Indeed, although certain acetogens can form fermentative end products such as ethanol (8, 39), acetogens are commonly thought to route the reductant derived from glycolysis toward the respiration of CO 2 to acetate (12,16,44).…”

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Effect of CO2 on the fermentation capacities of the acetogen Peptostreptococcus productus U-1

Misoph

Drake

1996

J Bacteriol

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The fermentative capacities of the acetogenic bacterium Peptostreptococcus productus U-1 (ATCC 35244) were examined. Although acetate was formed from all the substrates tested, additional products were produced in response to CO 2 limitation. Under CO 2 -limited conditions, fructose-dependent growth yielded high levels of lactate as a reduced end product; lactate was also produced under CO 2 -enriched conditions when fructose concentrations were elevated. In the absence of supplemental CO 2 , xylose-dependent growth yielded lactate and succinate as major reduced end products. Although supplemental CO 2 and acetogenesis stimulated cell yields on fructose, xylose-dependent cell yields were decreased in response to CO 2 and acetogenesis. In contrast, glycerol-dependent growth yielded high levels of ethanol in the absence of supplemental CO 2 , and pyruvate was subject to only acetogenic utilization independent of CO 2 . CO 2 pulsing during the growth of CO 2 -limited fructose cultures stopped lactate synthesis immediately, indicating that CO 2 -limited cells were nonetheless metabolically poised to respond quickly to exogenous CO 2 . Resting cells that were cultivated at the expense of fructose without supplemental CO 2 readily consumed fructose in the absence of exogenous CO 2 and formed only lactate. Although the specific activity of lactate dehydrogenase was not appreciably influenced by supplemental CO 2 during cultivation, cells cultivated on fructose under CO 2 -enriched conditions displayed minimal capacities to consume fructose in the absence of exogenous CO 2 . These results demonstrate that the utilization of alternative fermentations for the conservation of energy and growth of P. productus U-1 is augmented by the relative availability of CO 2 and growth substrate.Acetogenic bacteria utilize CO 2 as a terminal electron acceptor and synthesize acetate by the acetyl coenzyme A (acetyl-CoA) Wood/Ljungdahl pathway (12,16,35,36,44). The reduction of CO 2 to acetate is coupled to respiratory conservation of energy via either membranous electron transport or sodium pumping systems (11,27,33). Although supplemental CO 2 can be essential or greatly stimulatory to acetogenesis under certain conditions, acetogens can use other respiratory reductant sinks (15,17,18), including aromatic acrylate groups (2,22,32,40), fumarate (13, 31), dimethyl sulfoxide (3), and nitrate (20,37).In contrast to the numerous studies that have evaluated the respiratory capacities of acetogens, the fermentation capacities of this bacteriological group have been minimally examined. Indeed, although certain acetogens can form fermentative end products such as ethanol (8, 39), acetogens are commonly thought to route the reductant derived from glycolysis toward the respiration of CO 2 to acetate (12,16,44). The acetogenic sewage isolate Peptostreptococcus productus U-1 has been reported to form lactate (28). Although lactate production by P. productus U-1 has not been quantitatively examined, preliminary studies in our laboratory indicated th...

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Nitrate as a preferred electron sink for the acetogen Clostridium thermoaceticum

Cited by 86 publications

References 25 publications

Sporomusa silvacetica sp. nov., an Acetogenic Bacterium Isolated from Aggregated Forest Soil

Sporomusa silvacetica sp. nov., an Acetogenic Bacterium Isolated from Aggregated Forest Soil

Dissection of the Caffeate Respiratory Chain in the Acetogen Acetobacterium woodii : Identification of an Rnf-Type NADH Dehydrogenase as a Potential Coupling Site

Effect of CO2 on the fermentation capacities of the acetogen Peptostreptococcus productus U-1

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