Mikrobiologische Studien zur anaeroben Oxidation von Methan (AOM)

Abstract

Biogeochemical and molecular biological studies revealed new insights into the anaerobic oxidation of methane (AOM), but physiological aspects remained mostly unclear. Here incubation-experiments on AOM were performed, which gave insights into the physiology of the organisms. With sediment samples from Hydrate Ridge the dependence of sulphate-reduction on methane was shown, as well as the 1:1 stoichiometry. Vertical activity profiles confirmed that higher methane fluxes lead to higher activity. AOM showed a dependence on temperature, Hydrate Ridge samples were psychrophilic while samples from the Black Sea were mesophilic. Elevated methane partial pressure had a strong effect and increased the activity 2 to 5fold. Since AOM is most probably a syntrophic process by a sulphate-reducer and a methane-oxidizer we tried to find the intermediate that is exchanged between them. But non of the discussed and tested ones (H2, acetate, formate, methanol) seems to be the one in question. BES however stopped the AOM activity, indicating, that one of the partners is a methanogen operating in reverse. Molybdate only stopped the activity in Hydrate Ridge samples. In Black Sea samples the activity was only reduced. Antibiotics only active against bacteria did not effect the process of AOM. It was possible to increase the activity of the samples by continuously incubating them under elevated methane partial pressure (1,37MPa) and a regular exchange of the medium to supply the organisms with sulphate and methane and to remove sulphide. In 20 month the activity increased 6,5fold and also the amount of consortia increased significantly. The assumed doubling time of a consortium is 4.7 month. The classical isolation of sulphate-reducing-bacteria and methanogens seperatly lead to a number of strains, non of which however was closely elated to the members in the consortia. Also co-culture experiments did not reveal their ability to oxidize methane.