Nitrite and nitrous oxide production by Methylosinus trichosporium

Abstract

Conditions for the production of nitrite and nitrous oxide by an obligate methanotroph, M. trichosporium (OB 3b), were studied. The rate of nitrite production (VNO2-) was correlated with the concentration of ammonia up to 20 mM in the presence of sufficient amounts of O2 and inversely correlated with the amounts of methane in the system. The rate of N2O production (VN2O) was correlated positively with VNO2- and the amount of nitrite produced, and inversely with the O2 concentration in the system. Nitrite started to disappear when O2 or methane or both were depleted, but only a part of the loss could be accounted for by an increase in N2O. Maximum rates of nitrite and N2O production by M. trichosporium were 6.9 .times. 10-16 and 2.2 .times. 10-17 mol .cntdot. cell-1 .cntdot. day-1, respectively. These values are .apprx. 0.2 and 1.6% of the values for Nitrosomonas europaea. Production of nitrite and N2O by methanotrophs in aquatic environments may not be as significant as that of Nitrosomonas.