Purification and properties of ferredoxin from<i>Ruminococcus albus</i>

Tewes, Friederike; Thauer, Rudolf K.

doi:10.1111/j.1574-6968.1979.tb03746.x

Cited by 2 publications

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“…The ability of R. albus to hydrolyze and ferment the major plant cell wall polysaccharides, cel- In the experiment, ferredoxin from C. pasteurianum was used, which harbors two [4Fe4S] clusters and accepts two electrons at almost the same redox potential of Ϫ400 mV (87). The ferredoxin of C. pasteurianum is very similar to that of R. albus (19). lulose and hemicellulose, is the reason for the renewed biotechnological interest in this organism (4, 69).…”

Section: Discussionmentioning

confidence: 99%

“…In addition, it was difficult to envisage thermodynamically how NADH with a redox potential, E=, in vivo that was more positive than Ϫ320 mV (13,17) could provide the electrons for hydrogen formation from protons at a redox potential that was more negative than Ϫ400 mV considering that H 2 can be observed bubbling out of the medium when R. albus grows at pH 7 in the absence of a H 2 -consuming partner. The E 0 = of the 2ϫ[4Fe4S] ferredoxin from R. albus is Ϫ420 mV (18,19). In vivo, the E= of the ferredoxin is probably near the E 0 = of the acetylCoA ϩ CO 2 /pyruvate couple, which is Ϫ500 mV (20).…”

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Hydrogen Formation and Its Regulation in Ruminococcus albus: Involvement of an Electron-Bifurcating [FeFe]-Hydrogenase, of a Non-Electron-Bifurcating [FeFe]-Hydrogenase, and of a Putative Hydrogen-Sensing [FeFe]-Hydrogenase

et al. 2014

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bRuminococcus albus 7 has played a key role in the development of the concept of interspecies hydrogen transfer. The rumen bacterium ferments glucose to 1.3 acetate, 0.7 ethanol, 2 CO 2 , and 2.6 H 2 when growing in batch culture and to 2 acetate, 2 CO 2 , and 4 H 2 when growing in continuous culture in syntrophic association with H 2 -consuming microorganisms that keep the H 2 partial pressure low. The organism uses NAD ؉ and ferredoxin for glucose oxidation to acetyl coenzyme A (acetyl-CoA) and CO 2 , NADH for the reduction of acetyl-CoA to ethanol, and NADH and reduced ferredoxin for the reduction of protons to H 2 . Of all the enzymes involved, only the enzyme catalyzing the formation of H 2 from NADH remained unknown. Here, we report that R. T he genus Ruminococcus (class Clostridia) consists of species of anaerobic, Gram-positive bacteria. One or more species of this genus are found in significant numbers in the intestines of humans (enterotype 3) (1, 2) and in the rumen and colon of herbivores (3, 4). Ruminococcus flavefaciens and Ruminococcus albus are among the most important plant cell wall-degrading bacteria in the rumen. These two species produce all required enzymes for hydrolyzing the plant cell wall polysaccharides, cellulose and hemicellulose (5, 6).R. albus was isolated in 1957 from the rumen of cattle by Hungate (7,8), who showed that in batch culture the bacterium ferments cellulose, cellobiose, or glucose to acetate, CO 2 , ethanol, and H 2 . Nevertheless, neither H 2 nor ethanol accumulate to high concentrations in the rumen (9, 10). The low H 2 concentrations in the rumen have been explained by the presence of H 2 -consuming microorganisms, such as Methanobrevibacter ruminantium (formerly Methanobacterium ruminantium), that consume H 2 more rapidly than it is formed from cellulose by R. albus (11). The laboratory of Bryant and Wolin then showed in 1973 that the fermentation of glucose by R. albus strain 7 was shifted from 1.3 acetic acid, 0.7 ethanol, 2 CO 2 , and 2.6 H 2 in batch culture to 2 acetic acid, 2 CO 2 , and 4 H 2 in chemostat culture together with Wolinella succinogenes (formerly Vibrio succinogenes), which grew on H 2 and fumarate producing succinate, keeping the H 2 concentration low (12). The interspecies cooperation allowed W. succinogenes to grow at the expense of H 2 produced by R. albus, but it also offered an energetic advantage to R. albus in the form of a higher ATP gain (4 mol of ATP instead of 3.3 mol of glucose fermented) and, consequently, a better growth yield (13). At low H 2 partial pressures, the free energy associated with glucose fermentation is more negative than that at high H 2 partial pressures, which is the thermodynamic basis for the different ATP gains (13). The fermentation of R. albus on glucose has been modeled (14). The literature on interspecies H 2 and formate transfer has been reviewed recently (15).Enzymatic analyses have revealed that R. albus strain 7 grown in batch culture on glucose contains an NAD-specific glyceraldehyde-3-phosphate dehydr...

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%