High Concentrations of Methyl Fluoride Affect the Bacterial Community in a Thermophilic Methanogenic Sludge

To precisely control the application of methyl fluoride (CH(3)F) for analysis of methanogenic pathways, the influence of 0–10% CH(3)F on bacterial and archaeal communities in a thermophilic methanogenic sludge was investigated. The results suggested that CH(3)F acts specifically on acetoclastic methanogenesis. The inhibitory effect stabilized at an initial concentration of 3–5%, with around 90% of the total methanogenic activity being suppressed, and a characteristic of hydrogenotrophic pathway in isotope fractionation was demonstrated under this condition. However, extended exposure (12 days) to high concentrations of CH(3)F (>3%) altered the bacterial community structure significantly, resulting in increased diversity and decreased evenness, which can be related to acetate oxidation and CH(3)F degradation. Bacterial clone library analysis showed that syntrophic acetate oxidizing bacteria Thermacetogenium phaeum were highly enriched under the suppression of 10% CH(3)F. However, the methanogenic community did not change obviously. Thus, excessive usage of CH(3)F over the long term can change the composition of the bacterial community. Therefore, data from studies involving the use of CH(3)F as an acetoclast inhibitor should be interpreted with care. Conversely, CH(3)F has been suggested as a factor to stimulate the enrichment of syntrophic acetate oxidizing bacteria.