Decoding Microbial Responses to Ammonia Shock Loads in Biogas Reactors through Metagenomics and Metatranscriptomics

Area of Science:

• Microbiology
• Biotechnology
• Environmental Science

Background:

• Elevated ammonia concentrations are a major challenge in biogas production, inhibiting microbial processes.
• Understanding microbial responses to ammonia stress is crucial for optimizing biogas plant efficiency.

Purpose of the Study:

• To investigate the biogas microbiome's response to ammonia shock loads using multi-omics data.
• To identify microbial adaptation mechanisms and metabolic shifts under high ammonia conditions.

Main Methods:

• Combined biochemical, genome-centric metagenomic, and metatranscriptomic analyses.
• Analysis of a complex microbial community comprising 364 Metagenome Assembled Genomes (MAGs).
• Investigated microbial responses to ammonia concentrations of 1.5 g NH4+/LR and 5 g NH4+/LR.

Main Results:

• The hydrogenotrophic pathway dominated methane production, even at high ammonia levels.
• Specific methanogens (Methanothrix sp. MA6, Methanosarcina flavescens MX5) shifted from acetoclastic to CO2 reduction pathways.
• Upregulation of genes involved in osmoprotection demonstrated a key role in ammonia stress recovery.

Conclusions:

• The biogas microbiome utilizes the hydrogenotrophic pathway and osmoprotection for ammonia stress resilience.
• Metabolic flexibility in methanogens contributes to adaptation under high ammonia conditions.
• This research provides insights into the transcriptional mechanisms enabling anaerobic digestion communities to recover from ammonia-induced stress.