Integrated Metagenomic and Metaproteomic Analyses Unravel Ammonia Toxicity to Active Methanogens and Syntrophs, Enzyme Synthesis, and Key Enzymes in Anaerobic Digestion

Abstract

During anaerobic digestion, the active microbiome synthesizes enzymes by transcription and translation, and then enzymes catalyze multistep bioconversions of substrates before methane being produced. However, little information is available on how ammonia affects truly active microbes containing the expressed enzymes, enzyme synthesis, and key enzymes. In this study, an integrated metagenomic and metaproteomic investigation showed that ammonia suppressed not only the obligate acetotrophic methanogens but also the syntrophic propionate and butyrate oxidation taxa and their assistant bacteria (genus Desulfovibrio), which declined the biotransformations of propionate and butyrate → acetate → methane. Although the total population of the hydrolyzing and acidifying bacteria was not affected by ammonia, the bacteria with ammonia resistance increased. Our study also revealed that ammonia restrained the enzyme synthesis process by inhibiting the RNA polymerase (subunits A′ and D) during transcription and the ribosome (large (L3, L12, L13, L22, and L25) and small (S3, S3Ae, and S7) ribosomal subunits) and aminoacyl-tRNA synthesis (aspartate-tRNA synthetase) in translation. Further investigation suggested that methylmalonyl-CoA mutase, acetyl-CoA C-acetyltransferase, and CH 3 -CoM reductase, which regulate propionate and butyrate oxidation and acetoclastic methanation, were significantly downregulated by ammonia. This study provides intrinsic insights into the fundamental mechanisms of how ammonia inhibits anaerobic digestion.

Hormesis-Like Effects of Tetrabromobisphenol A on Anaerobic Digestion: Responses of Metabolic Activity and Microbial Community

“…This might be attributed to their similar special functions toward acid production; an in-depth investigation into this would be conducted with the assistance of multi-omics techniques. 13 The total abundance of acetogens showed similar variations with acidogens in response to TBBPA (11.8 versus 12.2 versus 10.8%). The abundances of Longilinea sp.…”

“…However, the total abundance values of acidogens in the three reactors were similar (56.6 versus 53.7 versus 56.9%), being in accordance with the Venn analysis results in Figure S6. This might be attributed to their similar special functions toward acid production; an in-depth investigation into this would be conducted with the assistance of multi-omics techniques . The total abundance of acetogens showed similar variations with acidogens in response to TBBPA (11.8 versus 12.2 versus 10.8%).…”

“…Anaerobic digestion is a complex ecosystem in which various microbial species (e.g., acidogens, acetogens, and methanogens) interact with each other to form a complicated network. , Through such network interactions, anaerobic digestion transforms organic matter into methane, which cannot be accomplished by an individual population. , Regardless of engineered and natural environments like anaerobic digesters and sediments, anaerobic digestion is a vital process closely related with carbon cycles, and generally co-exists with TBBPA. It is expected that the presence of TBBPA might alter the functional microbial species involved in such network and thereby affects the anaerobic digestion process and corresponding carbon cycles.…”

Amino Acid Configuration Affects Volatile Fatty Acid Production during Proteinaceous Waste Valorization: Chemotaxis, Quorum Sensing, and Metabolism

“…The TSS was analyzed by standard methods. The VFA composition and concentration were assayed according to publications. , …”

“…The VFA composition and concentration were assayed according to publications. 12,39 Statistical Analysis. Unless otherwise stated, all tests were carried out in triplicate, and the results were expressed as the mean ± standard deviation.…”