Vn. Khmelenina et al., Potential activity of methane and ammonium oxidation by methanotrophic communities from the soda lakes of Southern Transbaikal, MICROBIOLOG, 69(4), 2000, pp. 460-465
Radioisotopic measurements of the methane consumption by mud samples taken
from nine Southern Transbaikal soda lakes (pH 9.5-10.6) showed an intense o
xidation of methane in the muds of Lakes Khuzhirta, Bulamai Nur, Gorbunka,
and Suduntuiskii Torom, with the maximum oxidation rate in the mud of Lake
Khuzhirta (33.2 nmol/(ml day)). The incorporation rate of the radioactive l
abel from (CH4)-C-14 into (CO2)-C-14 was higher than into acid-stable metab
olites. Optimum pH values for methane oxidation in water samples were 7-8,
whereas mud samples exhibited two peaks of methane oxidation activity (at p
H 8.15-9.4 and 5.8-6.0). The majority of samples could oxidize ammonium to
nitrites; the oxidation was inhibited by methane. The PCR amplification ana
lysis of samples revealed the presence of genes encoding soluble and partic
ulate methane monooxygenase and methanol dehydrogenase. Three alkaliphilic
methanotrophic bacteria of morphotype I were isolated from mud samples in p
ure cultures, one of which, B5, was able to oxidize ammonium to nitrites at
pH 7-11. The data obtained suggest that methanotrophs are widely spread in
the soda lakes of Southern Transbaikal, where they can actively oxidize me
thane and ammonium.