A metagenomic assessment of microbial communities in anaerobic bioreactors and sediments: Taxonomic and functional relationships.

The present study used metagenomic sequencing, metagenome assembly and physical-chemical analysis to describe taxonomically and functionally 3 anaerobic bioreactors treating manure (LI), brewery (BR) and cornmeal (CO) wastes, and an anaerobic estuarine sediment (ES). Proteobacteria, Firmicutes, Euryarchaeota and Bacteroidetes were the most abundant Phyla in all metagenomes. A bacteria/archaea ratio of 3.4 was found in the industrial full-scale anaerobic bioreactors BR and CO, while ratios greater than 10 were found for LI and ES. Canonical correspondence analysis showed that environmental variables such as chemical oxygen demand, lipid content, and ammonium nitrogen influenced the ordination of taxonomic groups. Mesotoga prima was linked to high-temperature conditions, particularly in the BR bioreactor, along with the presence of heat shock proteins genes. Likewise, the hydrogenotrophic methanogen, Methanoregula formicica, was associated with high ammonium concentration in LI bioreactor. The interactions of microbes with specific methanogenic pathways were identified using Clusters of Orthologous Groups (COG) functions, while metagenome-assembled genomes (MAGs) further confirmed relationships between taxa and functions. Our results provide valuable information to understand microbial processes in anaerobic environments.