Kinetic studies of ammonia monooxygenase inhibition in Nitrosomonas europaea by hydrocarbons and halogenated hydrocarbons in an optimized whole-cell assay

Article Abstract:

The impact of 15 hydrocarbons and halogenated hydrocarbons on NH3 oxidation by ammonia monooxygenase (AMO) in intact cells of the nitirfying bacterium Nitrosomonas europaea were evaluated. Most inhibitors displayed competitive or non competitive exhibition patterns. AMO activity measured as NO2 production required coupling of hydroxylamine oxidoreductase (HAO) activity with NH3-dependent NH2OH production by AMO. The competitive character decreased as the molecular size of the inhibitors increased. Multichlorinated compounds gave non-linear Limeweaver-Burk plots. Maximum rates of NH3, C2H4 and C2H6 oxidation were roughly equivalent, implying a common rate-determining step.

Analysis, Chemical reaction, Rate of, Chemical kinetics, Ammonium compounds, Ammonium salts

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Ammonium limitation results in the loss of ammonia-oxidizing activity in Nitrosomonas europaea

Article Abstract:

Research was conducted to examine autotrophic ammonia oxidation which has been largely characterized at the molecular level in Nitrosomonas europaea, an obligate ammonia-oxidizing soil bacterium. Nitrite production and ammonia- and hydroxylamine-dependent oxygen consumption rates were monitored in incubated cells in growth medium containing 0, 5 and 50 mM ammonium. Results indicate that ammonia monooxygenase (AMO) substrates can protect AMO or other molecules associated with ammonia oxidation, thereby preserving the ammonia-oxidizing function of N europaea.

Microbial metabolism, Ammonium, Molecular microbiology

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Loss of ammonia monooxygenase activity in Nitrosomonas europaea upon exposure to nitrite

Article Abstract:

A study was conducted to analyze the loss of ammonia monooxygenase activity in Nitrosomonas europaea after nitrite exposure. The loff oa ammonio monooxygenase activity came under aerobic and anaerobic conditions. Results indicated that the nitrite toxicity in N. europaea is influenced by a novel mechanism specific for ammonia monooxygenase. However, during the presence of substrates of ammonia monooxygenase, the loss was not observed.

Bacteria, Ammonia, Nitrites

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