Activity and community structure of methane-oxidising bacteria in a wet meadow soil

Abstract

The structure and activity of the methane-oxidising microbial community in a wet meadow soil in Germany were investigated using biogeochemical, cultivation, and molecular fingerprinting techniques. Both methane from the atmosphere and methane produced in anaerobic subsurface soil were oxidised. The specific affinity (first-order rate constant) for methane consumption was highest in the top 20 cm of soil and the apparent half-saturation constant was 137^300 nM CH 4 , a value intermediate to measured values in wetland soils versus well-aerated upland soils. Most-probable-number (MPN) counting of methane-oxidising bacteria followed by isolation and characterisation of strains from the highest positive dilution steps suggested that the most abundant member of the methane-oxidising community was a Methylocystis strain (10 5^1 0 7 cells g 31 d.w. soil). Calculations based on kinetic data suggested that this cell density was sufficient to account for the observed methane oxidation activity in the soil. DNA extraction directly from the same soil samples, followed by PCR amplification and comparative sequence analyses of the pmoA gene, also detected Methylocystis. However, molecular community fingerprinting analyses revealed a more diverse and dynamic picture of the methane-oxidising community. Retrieved pmoA sequences included, besides those closely related to Methylocystis spp., others related to the genera Methylomicrobium and Methylocapsa, and there were differences across samples which were not evident in MPN analyses. ß

Plant species, temperature, and bedrock affect net methane flux out of grassland and forest soils

“…Our results show that methanotrophic bacteria are important members of the soil community, present in numbers of about 10 7 to 10 8 pmoA gene copies per gram dry weight of soil. The measured abundance is comparable to population sizes of methanotrophs found in other upland soils ranging from 10 5 to 10 7 cells per gram dry weight of soil (Willison et al 1997;Horz et al 2002). qPCR results and the measured methane fluxes emphasize that methanotrophs are apparently of ecological relevance concerning CH 4 uptake.…”

Two isozymes of particulate methane monooxygenase with different methane oxidation kinetics are found in Methylocystis sp. strain SC2

“…Although the pMMO2 presumably allows type II methanotrophs to survive in dry upland soils for extended periods by consuming atmospheric methane, the overall activity response of strain SC2 during incubation at 1.75 ppmv CH 4 , including the slight decline in cell numbers, implies that these methanotrophic bacteria may not be sufficiently oligotrophic for permanent activity in this type of soil. Rather, the presence of two pMMO isozymes with different thresholds for methane oxidation suggests that these organisms play an important role in consuming atmospheric methane if their growth is periodically supported by methane produced in anoxic microsites, in anoxic deep soil layers, or during temporary flooding (11,(27)(28)(29). In support of this view, Methylocystis spp.…”

Methanotrophic bacteria in oilsands tailings ponds of northern Alberta

“…Nitrogen is not limited in the ponds, in fact some nitrifying bacteria were detected (Supplementary Figure S2). However, the high ammonia/ammonium concentrations up to 17 mg l À 1 should require that methanotrophic species have mechanisms to deal with the toxic byproducts of ammonia oxidation by pMMO (Stein and Klotz, 2011 (Amaral and Knowles, 1995;Henckel et al, 1999;Henckel et al, 2000, van Bodegom et al, 2001Horz et al, 2002;Pester et al, 2004;Bussmann et al, 2006). Methane and O 2 levels certainly affect methanotroph communities, but the effect is probably sitespecific and difficult to generalize.…”