biosolids Metagenome

The use of treated municipal wastewater residues (biosolids) as fertilizers is an attractive, inexpensive option for growers and farmers. Various regulatory bodies typically employ indicator organisms (Fecal coliforms, E. coli and Salmonella) to assess the adequacy and efficiency of the wastewater treatment process in reducing pathogen loads in the final product. Presence of these organisms after the treatment is used as an indicator of potential contamination with pathogenic species. The routine tests currently rely on culture-based methods and thus can only detect viable and cultivable microorganisms. Molecular detection approaches can offer some advantages over culture-based methods as they can simultaneously detect a wider microbial species range, including non-cultivable microorganisms, however, they cannot directly assess the viability of the pathogen. Molecular methods infer the microorganism’s presence though detection of its DNA signature thus indicating that a pathogenic species was present at some point during the wastewater treatment but traditional cultivation methods to confirm its presence in a viable form in the final product is required in order to make any inference as to the product’s risk profile. Here, we used bacterial enumeration methods together with molecular methods including qPCR, 16S rRNA and cpn60 gene amplicon sequencing and shotgun metagenomic sequencing to compare pre- and post-treatment biosolids from two Canadian wastewater treatment plants (WWTPs).