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Appl Environ Microbiol, March 1998, p. 922-929, Vol. 64, No. 3
Institute of Microbiology, Russian Academy of
Sciences, Moscow 117811, Russia,1 and
Center for Microbial Ecology, Michigan State University, East
Lansing, Michigan 48824-13252
Received 26 June 1997/Accepted 5 December 1997
Highly enriched methanotrophic communities (>25 serial transfers)
were obtained from acidic ombrotrophic peat bogs from four boreal
forest sites. The enrichment strategy involved using media conditions
that were associated with the highest rates of methane uptake by the
original peat samples, namely, the use of diluted mineral medium of low
buffering capacity, moderate incubation temperature (20°C), and pH
values of 3 to 6. Enriched communities contained a mixture of
rod-shaped bacteria arranged in aggregates with a minor contribution of
Hyphomicrobium-like cells. The growth stoichiometry of
isolates was characteristic of methanotrophic bacteria
(CH4/O2/CO2=1:1.1:0.59), with an
average apparent yield of 0.41 ± 0.03 g of biomass C/g of
CH4-C. DNA from each enrichment yielded a PCR product of
the expected size with primers for both mmoX and
mmoY genes of soluble methane monooxygenase. Two types of
sequences were obtained for PCR-amplified fragments of
mmoX. One of them exhibited high identity to the
mmoX protein of the Methylocystis-Methylosinus
group, whereas the other showed an equal level of divergence from both
the Methylosinus-Methylocystis group and
Methylococcus capsulatus (Bath) and formed a distinct branch. The pH optimum for growth and for CH4 uptake was
4.5 to 5.5, which is very similar to that for the optimum
CH4 uptake observed in the original peat samples. These
methanotrophs are moderate acidophiles rather than acidotolerant
organisms, since their growth rate and methane uptake were much lower
at neutral pH. The growth of the methanotrophic community was enhanced
by using media with a very low salt content (20 to 200 mg/liter), more
typical of their natural environment. All four enriched communities grew on N-free medium.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Acidophilic Methanotrophic Communities from
Sphagnum Peat Bogs
*
Corresponding author. Mailing address: Institute of
Microbiology, Russian Academy of Sciences, Moscow 117811, Russia.
Phone: (095) 135-1171. Fax: (095) 135-6530. E-mail:
panikov{at}imbran.msk.su.
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