Influence of nitrate and nitrite concentration on N O production via dissimilatory nitrate/nitrite reduction to ammonium in Bacillus paralicheniformis LMG 6934.

Until now, the exact mechanisms for N O production in dissimilatory nitrate/nitrite reduction to ammonium (DNRA) remain underexplored. Previously, we investigated this mechanism in Bacillus licheniformis and Bacillus paralicheniformis, ubiquitous gram-positive bacteria with many industrial applications, and observed significant strain dependency and media dependency in N O production which was thought to correlate with high residual NO . Here, we further studied the influence of several physicochemical factors on NO (or NO ) partitioning and N O production in DNRA to shed light on the possible mechanisms of N O production. The effects of NO concentrations under variable or fixed C/N-NO ratios, NO concentrations under variable or fixed C/N-NO ratios, and NH concentrations under fixed C/N-NO ratios were tested during anaerobic incubation of soil bacterium B. paralicheniformis LMG 6934 (previously known as B. licheniformis), a strain with a high nitrite reduction capacity. Monitoring of growth, NO , NO , NH concentration, and N O production in physiological tests revealed that NO as well as NO concentration showed a linear correlation with N O production. Increased NO concentration under fixed C/N-NO ratios, NO concentration, and NH concentration had a significant positive effect on NO (or NO ) partitioning ([N-NH ]/[N-N O]) toward N O, which may be a consequence of the (transient) accumulation and subsequent detoxification of NO . These findings extend the information on several physiological parameters affecting DNRA and provide a basis for further study on N O production during this process.