title: Response of methanotrophic activity and community structure to temperature changes in a diffusive CH/O counter gradient in an unsaturated porous medium.
abstract: Microbial methane oxidation is a key process in the global methane cycle. In the context of global warming, it is important to understand the responses of the methane-oxidizing microbial community to temperature changes in terms of community structure and activity. We studied microbial methane oxidation in a laboratory-column system in which a diffusive CH(4)/O(2) counter gradient was maintained in an unsaturated porous medium at temperatures between 4 and 20 degrees C. Methane oxidation was highly efficient at all temperatures, as on average 99 +/- 0.5% of methane supplied to the system was oxidized. The methanotrophic community that established in the model system after initial inoculation appeared to be able to adapt quickly to different temperatures, as methane emissions remained low even after the system was subjected to abrupt temperature changes. FISH showed that Type I as well as Type II methanotrophs were probably responsible for the observed activity in the column system, with a dominance of Type I methanotrophs. Cloning and sequencing suggested that Type I methanotrophs were represented by the genus Methylobacter while Type II were represented by Methylocystis. The results suggest that in an unsaturated system with diffusive substrate supply, direct effects of temperature on apparent methanotrophic activity and community may be of minor importance. However, this remains to be verified in the field.
authors.affiliation: ETH Zurich, Institute of Biogeochemistry and Pollutant Dynamics, Zurich, Switzerland.
authors.forename: Karina
authors.initials: K
authors.lastname: Urmann
authors.forename: Anna
authors.initials: A
authors.lastname: Lazzaro
authors.forename: Isabella
authors.initials: I
authors.lastname: Gandolfi
authors.forename: Martin H
authors.initials: MH
authors.lastname: Schroth
authors.forename: Josef
authors.initials: J
authors.lastname: Zeyer
mesh_terms: D002245:Carbon Dioxide / Q000032:analysis; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D005798:Genes, Bacterial; D017404:In Situ Hybridization, Fluorescence; D008697:Methane / Q000032:analysis / Q000378:metabolism*; D042083:Methylocystaceae / Q000235:genetics / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000032:analysis / Q000378:metabolism*; D012150:Polymorphism, Restriction Fragment Length; D016062:Porosity; D013696:Temperature
chemical_list: D004269:DNA, Bacterial; D002245:Carbon Dioxide; D008697:Methane; D010100:Oxygen