The Influence of Extracellular Hydrogen on the Metabolism of Bacteroides ruminicola, Anaerovibrio lipolytica and Selenomonas ruminantium

Abstract

I N T R O D U C T I O NWhen inhibitors of rumen methanogenic bacteria are fed to ruminants the resulting depression of methane production is accompanied by an accumulation of H, and an increase in the proportion of propionic acid relative to acetic acid in the rumen (Demeyer & Van Nevel, 1975). It may be that the accumulating H, so decreases growth of those rumen bacteria which form acetate as their main product (Hungate, 1966) as to allow the propionate-producing bacteria to compete more successfully for fermentable substrate. Alternatively, the H, produced by the acetate-producing bacteria might be used directly by the propionate producers to increase the proportion of pyruvate which is reduced to propionate and thus increase the ratio of propionate to acetate produced.In the present study several important propionate-and succinate-producing rumen bacteria were tested for their ability to utilize extracellular H, as a source of reducing power. Such activity has been shown to be the main source of energy for the nonfermentative rumen bacterium Vibrio succinogenes which requires an exogenous supply of H, (or formate) and fumarate (Wolin et al., 1961). The reduction of fumarate to succinate by V. succinogenes is accompanied by electron transport-linked phosphorylation (Reddy & Peck, 1978). M E T H O D SAnaerovibrio lipolytica 5s was the strain of Hobson (1965); it was grown on the medium described by Henderson (1971) with fructose as energy source. Selenomonas ruminantiurn strains 17 and WPLl 51 j l were isolated at the Rowett Research Institute as described by Hobson & Mann (1961); they were grown on medium H5 which was based on medium 1 of Kurihara et al. (1968) with rumen fluid replaced by distilled t

Nitrate reduction in bacteroides multiacidus: Its effect on glucose metabolism and some properties of the reductase.

“…Propionate was not found in any culture, even in those grown with yeast extract and hemin. This composition of products is similar to that found in B. ruminicola (26) rather than B, fragilis (2). If the bacterium had the same pathway for glucose metabolism as found in B, fragilis (27), succinate could be formed via the reduction of oxaloacetate made by addition of carbon dioxide to phosphoenolpyruvate.…”

“…Succinate formation in Bacteroides is thought to be associated with energy conservation by phosphorylation coupled to the anaerobic electron transfer through a cytochrome to fumarate (1,2,26). The levels of cell growth were slightly increased by nitrate reduction.…”

Gut bacteria–host metabolic interplay during conventionalisation of the mouse germfree colon

“…This correlation may have reflected a temporarily decreased utilisation of tricarboxylic acid cycle intermediates by the host (Figure 4b). Alternatively, these metabolites could have been derived from the bacterial metabolism, which would be in agreement with the capacity of the correlated bacterial groups to produce oxaloglutarate by reductive carboxylation of succinate (Henderson, 1980). Succinate was detected at high Figure 3A), Bacilli and scyllo-and myo-inositol tissue metabolites (a) (positive correlation).…”

Effects of disodium fumarate on ruminal fermentation and microbial communities in sheep fed on high-forage diets

“…Two of the sequences in band b were affiliated to Selenomonas ruminantium isolate M40 (AY685142.1; Table 6). Fumarate reduction has been reported Zhou, McSweeney, Wang and Liu to be catalyzed by fumarate reductase in P. ruminicola and S. ruminantium (Henderson, 1980). There is also evidence that S. ruminantium can utilize hydrogen produced by other rumen microorganisms (Marvin-Sikkema et al, 1990).…”