Methanogens in municipal solid waste landfill leachates

Archaeal microbial of MSW landfill leachates were characterized using a 16S rDNA approach. Phylogenetic affiliations of 241 rDNA sequences were determined. Sequences belonging to the Methanosarcinales order were dominant (60% were related to the strictly acetoclastic genus Methanosaeta). Sequences affiliated to the metabolically versatile genus Methanosarcina represented 22 % of the retrieved sequences and some members of the hydrogenotrophic order Methanomicrobiales were also recovered in limited numbers. Labscale incubations were performed with leachates mixed with several methanogenic precursors (acetate, hydrogen, formate, methanol, methylamine). During the incubations, acetoclastic methanogenesis was rapidly induced and lead to the dominance of archaea of the Methanosarcinaceae family. Hydrogen, formate, methanol and methylamine addition induced the onset of a homoacetogenesis. In these incubations, Methanosarcinaceae (hybridizing with probe MS1414) and Methanomicrobiales (hybridizing with probe EURY496) were dominant.