Metagenomic assessment of the microbial community and methanogenic pathways in biosolids from a municipal wastewater treatment plant in Medellín, Colombia

Abstract

Abundance and diversity of microbial communities in biosolids are variable and poorly studied in the tropics, and it is known that rainfall is one of the events that could affect the phylogenetic and functional microbial structure. In the present study, using NGS technics, we studied the microbial diversity as well as the methanogenesis path- way in one of the largest WWTP in Colombia. Besides, we sampled and analyzed biosolids from rainy season and dry season. Phylogenetic classi fi cation showed a predominance of bacteria in both samples and difference in the dominant groups depending on the rainfall season. Whereas Pseudomonas was the dominant bacteria in the dry season, Coprothermobacter was in the rainy season. Archaea abundance was higher in the rainy season (11.5%) doubling dry season proportion. The bioreactor biogas production and total solids content showed similar results between rainy and dry season at the sampling dates. The most abundant Archaea related with methanogenesis was Methanosaeta , which is a methanogenic microorganism that exclusively uses acetate to produce methane. More- over, annotation ofthe methanogenicpathway inthe metagenomeshowedabundancein genes encoding Acetyl- CoA synthetases(ACSS), an enzyme that catalyzes acetate activation. Ourresults suggest that the microbial diver- sity was stable among the two time points tested, rainy season and dry season; and, although there were changes in the microbial abundance of dominant bacterial species, anaerobic digester performance is not affected.