Effect of Dissolved Oxygen Tension on the Metabolism of Methylated Amines in Hyphomicrobium X in the Absence and Presence of Nitrate: Evidence for 'Aerobic' Denitrification

Abstract

Hyphomicrobium X possesses two different enzymes for the oxidation of dimethylamine, namely dimethylamine dehydrogenase and dimethylamine mono-oxygenase. During growth of the organism in batch culture at dissolved oxygen tensions (DOT) in excess of 30 mmHg in media containing trimethylamine as the carbon and energy source, dimethylamine mono-oxygenase was the only enzyme involved in dimethylamine oxidation. The apparent K, of the mono-oxygenase for oxygen was relatively high (23-2 ,uM). The enzyme was less sensitive to inhibition by trimethylamine (& 4.2 mM) than was dimethylamine dehydrogenase (K, 7.1 ,UM) and therefore dimethylamine did not accumulate in the culture medium under these conditions. This was in contrast to observations made during anaerobic growth on trimethylamine. During growth of the organism in dimethylamine-limited chemostat cultures, the specific activities of the mono-oxygenase and the dehydrogenase were dependent on the DOT in the culture. When the DOT in the culture growing at a dilution rate of 0-10 h-l was decreased below 30 mmHg, the activity of the mono-oxygenase also decreased. In contrast, the activity of dimethylamine dehydrogenase increased, indicating that this enzyme gradually took over at the lower DOT. Below values of 5 mmHg the culture became oxygen-limited and below 3 mmHg itwas washed out. When the organism was grown at low DOT in medium supplemented with nitrate, essentially the same results were obtained, except that wash-out of the culture under anaerobic conditions did not occur. The organism was able to carry out denitrification under 'partly aerobic ' conditions

Dynamic Simulation of Multinary Diffusion Problems Related to Soil

“…When nitrate is present and lo 2 < Co 2 < ho 2 , both aerobic respiration and denitrification occur. Increasing denitrification activity with decreasing oxygen tension in continuous culture studies of Hyphomicrobium X was reported by Meiberg et al (1980). When lc 2 H 2 < Cc 2 H 2 < hc 2 H 2 , the conversion of nitrous oxide to molecular nitrogen, Eq.…”

Aerobic denitrification — old wine in new bottles?

“…A second example of denitrification in the presence of low, but significant concentrations of dissolved oxygen was reported by Meiberg et al (1980). They found that with Hyphomicrobium X in chemostat cultures growing on dimethylamine, the induction of the denitrifying enzymes required the presence of nitrate, and also appeared to be linked to the growth rate.…”

Nitrate respiration in chemoautotrophic symbionts of the bivalve Lucinoma aequizonata

“…Free-living bacteria usually respire nitrate under anoxic conditions (Payne 1973, Stouthamer 1980, Tiedje 1988, only a few free-living bacteria are known for aerobic denitrification (Krul & Veeningen 1977, Meiberg et al 1980, Robertson & Kuenen 1984a, b, Lloyd et al 1987, Robertson et al 1988 or co-respiration of oxygen and nitrate (Bonin & Gilewicz 1991). These bacteria are denitrification specialists and do not shut down their denitrification enzymes in response to…”