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

Abstract

Bacteroides multiacidus fermented glucose to lactate and succinate as major products and produced small amounts of acetate and pyruvate. During nitrate reduction cell growth increased slightly and the formation of succinate and lactate decreased while acetate increased. The level of nitrate reductase activity in the extracts was several times higher in cells grown on nitrate, while the fumarate reductase level was lowered compared with cells not grown on nitrate. In extracts, nitrate reductase and fumarate reductase occurred mainly in a particulate fraction, whereas nitrite reductase was mostly in a soluble fraction. Addition of tungstate to the culture medium decreased the nitrate reductase activity as well as nitrite formation, suggesting that the enzyme is a molybdoprotein. Ferredoxin from Clostridia and viologen dyes served as electron donors for nitrate reduction. A c-type cytochrome with peaks at 557.5, 527, and 423 nm in the extract was partly reduced by NADH and oxidized by fumarate, and to a lesser extent also by nitrate, even in extracts from cells grown in the presence of nitrate. Km's for substrates and pH optima were also reported for the reductases in crude extracts.Bacteroides are strictly anaerobic, gram-negative, non-spore-forming and rod-shaped bacteria. They predominate in rumens and intestinal tracts. Some species of Bacteroides (1) are known to require hemin for maximum growth and to contain b-type cytochromes, which serve as electron carriers to fumarate reductase to form succinate. In addition, this cytochrome-linked fumarate reductase system couples with ATP formation in Bacteroides fragilis (2). Bacteroides multiacidus isolated from human feces (3) is one of the few species able to reduce nitrate to nitrite. The function of nitrate reduction in this bacterium and its influence on its host are not well understood.

Reduction of Ferric Iron by Heterotrophic Bacteria in Lake Sediments

“…The changes in fermentation end products observed in this study were similar to those seen following the addition of nitrate to the growth media of Bacteroides sp. (Yamamoto et al, 1982) and Clostridium sp. (Keith et al, 1982).…”

Influence of carbon-based cathodes on biofilm composition and electrochemical performance in soil microbial fuel cells

“…Other taxa were found enriched on either but not both SMFC-GF replicates, including Lacunisphaera (SMFC-GF1) and Faecalibacterium , Bacteroides , and Parabacteroides (SMFC-GF2) . Of these genera, Bacteroides have been reported to produce hydrogen [ 94 , 95 ], whereas the ability to reduce nitrate was reported for both Lacunisphaera and Bacteroides [ 96 , 97 ]. Since the redox potential of the NO 3 − /NO 2 − couple is +421 mV, likely, the peaks at 419 ± 20 mV observed for SMFC-GF in the CV tests (shown in Fig.…”