Microbial community in a Decentralized Wastewater Treatment System Raw sequence reads

Decentralized wastewater treatment system (DWTS) applied with anaerobic digestors has gained momentum worldwide, due to its ease of operation, high efficiency and recycling use of wastewater. The community structure of two different anaerobic bioreactors (primary sludge digestor, PSD; and anaerobic membrane bioreactor, AnMBR) in a DWTS located in Germany were investigated using 16S rRNA gene amplicon and metagnomic sequencing. The results showed that microbial community structure was remarkably different in PSD and AnMBR, and Methanobacteriaceae and Syntrophaceae were identified as the families that significantly differed in abundance between these two bioreactors (P < 0.05). We also use genome-centered metagenomics to predict the microbial interaction and methane-generating pathway, that yielded 22 near-complete were assembled genomes (MAGs) (average completeness of 93.0% and contamination of 2.9%) that together represent the majority of the microbial community. MAGs affiliated with methanogenic archaea including Methanobacterium sp., Methanomicrobiales archaeon, Methanomassiliicoccales archaeon, and Methanosaeta concilii, which were recruited, along with other syntrophic bacterial MAGs associated with anaerobic digestion. Key genes encoding enzymes involved in specific carbohydrate-active and methanogenic pathways in MAGs were identified to illustrate the microbial function and interaction during anaerobic digestion of wastewater treatment. From the MAG information, it was prediced that bacteria affiliated with Bacteroidetes, Prolixibacteraceae and Synergistaceae were the key bacteria roled in hydrolysis, fermentation and acetogenesis, respectively. In the last step of biological methane production, Methanobacterium sp. executed hydrogenotrophic methanogenesis, that reduced carbon dioxide to methane with hydrogen as the primary electron donor. This work provides a clear understanding of the methane-generating pathways and highlighting the syntrophic interaction during anaerobic digestion in DWTS.