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(089) Anaerobic degradation and methane production in aged lake sediments. Nozhevnikova, A.N.1, Simankova, M.V. 1, Nekrasova, V.K.1, Holliger, C.2, Wehrli, B.3, Zepp, K.3, 1 2 3 ABSTRACT- A sediment core of 9 m length was taken from Lake Baldegg (Switzerland) in November 1997. The age of the sediments in the lowest part of the core was not less than 10.000 years. Directly after retrieving the core it was brought to an anerobic chamber and sampled using sterile equipment. Subsequently the anaerobic microbial population was analysed by microbiological and molecular methods. After in situ hybridisation using fluorescently labeled probes Eub338 and Arch915 members of the targeted domains Bacteria and Archaea could be quantified in sediment layers which were up to 200 years old. Incubation of sediment slurries at temperatures from 5 to 50°C, enrichment on different substrates, and isolation of pure cultures showed that aged sediments contained different microorganisms, including thermophilic ones. Psychrophilic and mesophilic methanogenic microbial communities, that were able to degrade cellulose completely until the formation of methane, survived in the aged sediments up to the maximal depth of 870 cm (more than 10.000 years old). Thermophilic methanogenic community which was able to degrade cellulose completely, was enriched only from relatively young sediments (up to 300 years old). In contrast, thermophilic cellulolytic, fermentative and acetogenic bacteria were enriched even from 10.000 years old sediments. When hydrogen and carbondioxide mixture was used as a growth substrate, acetogenesis prevailed methanogenesis in young and aged sediments. Methane was formed later from acetate. The availability of the substrates and low temperature are the limiting factors in anaerobic degradation in aged sediments. Key words: aged lake sediments, anaerobic degradation, anaerobic bacteria, archea |
