The Reduction of Nitrate to Ammonium by a Clostridium sp. Isolated from Soil

Abstract

Cultures of Clostridium KDHS2 reduced 15NO3- to 15NH4+ with a concurrent increase in molar growth yield of 15.7% compared with fermentatively grown bacteria. The bacteria exhibited a Ks (NO3-) of 0.5 mM and reduced NO3- maximally at a rate of 0.1 mumol h(-1) mg dry wt)-1. A partially purified nitrate reductase was obtained which had a Km (NO3-) of 0.15 mM. The reduction of 13NO3- to 13NH4+ by resting bacteria was not inhibited by NH4+, glutamate, glutamine, methionine sulphoximine or azaserine. Glutamine synthetase affected neither the synthesis nor the activity of the NO3(-)-reducing enzymes. The results are consistent with the hypothesis that NO3- reduction to NH4+ in this Clostridium sp. is dissimilative. SO32-, but not SO42-, inhibited the reaction, apparently at the level of NO2- reduction.

Ecology of Microbial Cellulose Degradation

“…The reduction clearly has ecological implications and has been observed in soil (Buresh and Patrick, 1978;Caskey and Tiedje, 1980) and in marine sediments (Koike and Hattori, 1978;Serensen, 1978). Denitrification, a process discussed at length by Payne (1981) and Knowles (1982), may also occur.…”

“…Nitrate is reduced to ammonia in an anaerobic environment by some sulfate-reducing bacteria (Peck, 1984), as well as by other anaerobic bacteria (Caskey and Tiedje, 1980). The reduction clearly has ecological implications and has been observed in soil (Buresh and Patrick, 1978;Caskey and Tiedje, 1980) and in marine sediments (Koike and Hattori, 1978;Serensen, 1978).…”

Origin, causes and effects of increased nitrite concentrations in aquatic environments

“…DNRA is performed by fermentative bacteria (e.g., Enterobacteriaceae, Aeromonas, Vibrio spp., Clostridium sp. ), whereas denitrification is mediated by respiratory organisms (e.g., Pseudomonas and Bacillus species) (Caskey & Tiedje 1980; Cole 1996;Focht & Verstraete 1977). Nitrate and nitrite fermentation to ammonium is in direct competition with denitrification.…”

A heme- C -containing enzyme complex that exhibits nitrate and nitrite reductase activity from the dissimilatory iron-reducing bacterium Geobacter metallireducens

“…Although G. metallireducens is best known for its ability to respire Fe(III), it could also be a significant contributor to nitrate reduction in estuarine environments (Lovley 1991;Coates et al 1996). The apparent K m for nitrate (32 µM) is comparable to that of other nitrate-respiring bacteria, which have reported values ranging from 2 µM to 12 mM for denitrifiers (Hochstein and Tomlinson 1988;Murray et al 1989;Krause and Nealson 1997) and from 0.5 to 500 µM for nitrate ammonifiers (Caskey and Tiedje 1980;Dalsgaard and Bak 1994). The K m for nitrite (10 µM) also compares favorably with the values reported for the multiheme cytochrome c nitrite reductases in D. desulfuricans (1.1 mM) and E. coli (110 µM) (Liu and Peck 1981;Kajie and Anraku 1986).…”