Inhibitory Effects of Ammonia on Archaeal 16S rRNA Transcripts in Thermophilic Anaerobic Digester Sludge

High temperatures exacerbate the ammonia inhibition of anaerobic digestion coupled with methanogenesis. The methane production by has been observed in other studies. However, underlying mechanism is not well understood and requires further investigation. This study explored effect stress on archaeal 16S rRNA transcripts thermophilic digester sludge. Different ammonium concentrations were checked for their influence methanogenic rate hydrogen accumulation. Quantitative PCR was used to compare changes total expression. A Monte Carlo permutation test within redundancy analysis (RDA) adopted exploring relationship between environmental variables transcripts. results showed that increase concentration, decreased accumulation occurred. genes copy numbers significantly treatments higher (7 10 g NH4+-N/L), but did change much at lower (3 NH4+-N/L) compared 0 NH4+-N/L treatment. RDA revealed most variables, including methane, except formate, correlated community structure activity rather than genes. composition hydrogenotrophic methanogen Methanothermobacter dominated all incubations. It exhibited sensitivity should be responsible under conditions. Our findings suggested transcripts, genes, are key indicators activity.