Response of the rumen archaeal and bacterial populations to anti-methanogenic organosulphur compounds in continuous-culture fermenters

The study of methanogenesis inhibitors effectiveness in the rumen have shown inconsistent results, mainly due to poorly understood effects on the key microbial groups involved in methane CH4 synthesis pathways. This experiment was designed to assess the effect of propyl propane thiosulfinate (PTS), diallyl disulfide (DDS) and bromochloromethane (BCM) on rumen fermentation, methane production and microbial populations on continuous culture fermenters. No effects on total VFA were observed with PTS and DDS, while were decreased with BCM. Amylase activity increased with BCM compared to the other treatments. A decrease on methane production was observed with PTS (48%) and BCM (94%) compared to control. Concentration of methanogenic archaea decreased with BCM from day 4 onward and with PTS on days 4 and 8. The pyrosequencing analysis revealed that PTS and BCM decreased the relative abundance of Methanomicrobiales and increased that of Methanobrevibacter and Methanosphaera. The concentration of total bacteria was not modified by any treatment, although BCM treatment increased the relative abundance of Prevotella and decreased that of Ruminococcus. These results suggest that the inhibition of methane production in the rumen by PTS and BCM is associated with a shift in the archaeal biodiversity and changes in bacterial community with BCM.