In the actinomycete complexes of Mongolian desert soils, thermotolerant and thermophilic acti nomycetes were found in high abundance, exceeding that of the mesophilic forms. Among the thermotolerant members of the order Actinomycetales, Streptomyces, Micromonospora, Actinomadura, and Streptosporangium species were most widespread in desert soils. Experiments with soil microcosms demonstrated that thermo philic actinomycetes in desert soils grew, developed, and formed mycelia of the length comparable to that of the mesophilic forms of actinomycetes. Molecular biological investigation of the samples of desert steppe soils by denaturing gradient gel electrophoresis (DGGE) and fluorescent in situ hybridization (FISH) revealed members of the phylum Actinobacteria. FISH analysis revealed that the biomass of the metabolically active mycelial actinobacteria in the prokaryotic community of Mongolian desert soils exceeded that of the unicellular Actinobacteria.

No abstract

Aerobic methane oxidation has been mostly studied in environments with moderate to low temperatures. However, the process also occurs in terrestrial thermal springs, where little research on the subject has been done to date. The potential activity of methane oxidation and diversity of aerobic methanotrophic bacteria were studied in sediments of thermal springs with various chemical and physical properties, sampled across the Kunashir Island, the Kuriles archipelago. Activity was measured by means of the radioisotope tracer technique utilizing (14)C-labeled methane. Biodiversity assessments were based on the particulate methane monooxygenase (pmoA) gene, which is found in all known thermophilic and thermotolerant methanotrophs. We demonstrated the possibility of methane oxidation in springs with temperature exceeding 74 °C, and the most intensive methane uptake was shown in springs with temperatures about 46 °C. PmoA was detected in 19 out of 30 springs investigated and the number of pmoA gene copies varied between 10(4) and 10(6) copies per ml of sediment. Phylogenetic analysis of PmoA sequences revealed the presence of methanotrophs from both the Alpha- and Gammaproteobacteria. Our results suggest that methanotrophs inhabiting thermal springs with temperature exceeding 50 °C may represent novel thermophilic and thermotolerant species of the genera Methylocystis and Methylothermus, as well as previously undescribed Gammaproteobacteria.

Human activities such as land management and global warming have great impact on the environment. Among changes associated with the global warming, rising methane emission is a serious concern. Therefore, we assessed methane oxidation activity and diversity of aerobic methanotrophic bacteria in eight soil types (both unmanaged and agricultural) distributed across the European part of Russia. Using a culture-independent approach targeting pmoA gene, we provide the first baseline data on the diversity of methanotrophs inhabiting most typical soil types. The analysis of pmoA clone libraries showed that methanotrophic populations in unmanaged soils are less diverse than in agricultural areas. These clone sequences were placed in three groups of, so far, uncultured methanotrophs: USC-gamma, cluster I, and pmoA/amoA cluster, which are believed to be responsible for atmospheric methane oxidation in upland soils. Agricultural soils harbored methanotrophs related to genera Methylosinus, Methylocystis, Methylomicrobium, Methylobacter, and Methylocaldum. Despite higher numbers of detected molecular operational taxonomic units (MOTUs), managed soils showed decreased methane oxidation rates as observed in both in situ and laboratory experiments. Our results also suggest that soil restoration may have a positive effect on methane consumption by terrestrial ecosystems.

No abstract