Production and oxidation of methane at low temperature by the microbial population of municipal sludge checks situated in north-east Europe

Methanogenic and methane-oxidizing activities of the microbial population o f sewage sludge checks (Moscow and Syktyvkar regions) were studied at tempe ratures ranging from 5 to 25 degreesC. The number of methanogens in silt sa mples reached 10(10) cells/ml. A temperature decrease from 25 to 5 degreesC led to a sharp decrease of methanogenesis in the silt samples. Nevertheles s, methanogenesis was still significant even at 5 degreesC. Different organ ic substrates, including polymeric and aromatic compounds, were degraded wi th methane production at 6 degreesC. At depths of 20-40 cm the number of me thanotrophic bacteria reached 10(11) cells/ml. Methane oxidative activity o f the microbial populations in the silt was less sensitive to the 25 degree s to 5 degreesC temperature decrease. Ten methanotrophic species, able to g row at 6 degreesC, were enriched from the Syktyvkar sludge lagoon and ident ified by indirect immunofluorescence. Enrichments obtained from the Syktuvk ar region (62 N) contained more species of methane oxidizing bacteria able to grow at low temperature then methanogenic enrichments obtained from Mosc ow region (56 N).