Comparative Analysis of Bacterial and Archaeal Population Structure by Illumina Sequencing of 16S rRNA Genes in Three Municipal Anaerobic Sludge Digesters

Abstract Understanding the microbial communities in anaerobic digesters is important for better regulation, operation, and sustainable management of the sludge produced at various stages of wastewater treatment processes. Microbial communities in the anaerobic digester of the gulf region where the climatic conditions and other factors may impact the incoming feed have not been documented. Archaeal and Bacterial communities of three full-scale anaerobic digesters, namely AD1, AD3 and AD5 were analyzed by Illumina sequencing of 16S rRNA genes. Among bacteria, the most abundant genus was fermentative bacteria Acetobacteroides (Blvii28). Other predominant bacterial genera in the digesters included thermophilic bacteria (Fervidobacterium and Coprothermobacter) and halophilic bacteria like Haloterrigena and Sediminibacter. This can be correlated with the climatic condition in Dubai, where the bacteria in the original feed may be thermophilic or halophilic as much of the water used in the country is desalinated seawater. Propionic acid-producing bacteria like Paludibacter and propionate oxidizing bacteria like W5 were also dominating group and were found in all the digesters. The predominant Archaea include mainly the members of phylum Euryarchaeota and Crenarchaeota belonging to genus Methanocorpusculum, Metallosphaera, Methanocella, and Methanococcus. The highest population of Methanocorpusculum (more than 50% of total Archaea) hydrogenotrophic archaea matches with the high population of Acetobacteroides (Blvii28) and Fervidobacterium bacteria which ferments the organic substrates to acetate and H2. Coprothermobacter, which is known to improve protein degradation by establishing a syntrophy with hydrogenotrophic archaea, was also one of the dominant genera in the digesters. This study, for the first time, contributes to an in-depth understanding of the phylogenetic diversity of a microbial community of three full-scale anaerobic digesters of a municipal wastewater treatment plant in Dubai, UAE.