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Applied and Environmental Microbiology, May 2000, p. 1801-1808, Vol. 66, No. 5
Max-Planck-Institut für terrestrische
Mikrobiologie, Karl-von-Frisch-Strasse, 35043 Marburg, Germany
Received 1 October 1999/Accepted 7 January 2000
Forest and other upland soils are important sinks for atmospheric
CH4, consuming 20 to 60 Tg of CH4 per year.
Consumption of atmospheric CH4 by soil is a microbiological
process. However, little is known about the methanotrophic bacterial
community in forest soils. We measured vertical profiles of atmospheric
CH4 oxidation rates in a German forest soil and
characterized the methanotrophic populations by PCR and denaturing
gradient gel electrophoresis (DGGE) with primer sets targeting the
pmoA gene, coding for the
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Molecular Analyses of Novel Methanotrophic
Communities in Forest Soil That Oxidize Atmospheric Methane
subunit of the particulate
methane monooxygenase, and the small-subunit rRNA gene (SSU rDNA) of
all life. The forest soil was a sink for atmospheric CH4 in
situ and in vitro at all times. In winter, atmospheric CH4
was oxidized in a well-defined subsurface soil layer (6 to 14 cm deep),
whereas in summer, the complete soil core was active (0 cm to 26 cm
deep). The content of total extractable DNA was about 10-fold higher in
summer than in winter. It decreased with soil depth (0 to 28 cm deep)
from about 40 to 1 µg DNA per g (dry weight) of soil. The PCR product concentration of SSU rDNA of all life was constant both in winter and
in summer. However, the PCR product concentration of pmoA changed with depth and season. pmoA was detected only in
soil layers with active CH4 oxidation, i.e., 6 to 16 cm
deep in winter and throughout the soil core in summer. The same
methanotrophic populations were present in winter and summer. Layers
with high CH4 consumption rates also exhibited more bands
of pmoA in DGGE, indicating that high CH4
oxidation activity was positively correlated with the number of
methanotrophic populations present. The pmoA sequences
derived from excised DGGE bands were only distantly related to those of
known methanotrophs, indicating the existence of unknown
methanotrophs involved in atmospheric CH4 consumption.
*
Corresponding author. Mailing address:
Max-Planck-Institut für terrestrische Mikrobiologie,
Karl-von-Frisch-Strasse, 35043 Marburg, Germany. Phone:
49-6421-178801. Fax: 49-6421-178809. E-mail:
conrad{at}mailer.uni-marburg.de.
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