Predicting the potential for organohalide respiration in wastewater: Comparison of intestinal and wastewater microbiomes.

Halogenated compounds such as polychlorinated biphenyl (PCBs) and polybrominated diphenyl ethers (PBDEs) enter wastewater treatment plants (WWTPs) via the sewage system. These organic contaminants partition between the aqueous and the biosolid phase, where the former is discharged as wastewater effluent. Biosolids from a WWTP provide a hydrophobic surface for adsorption and thus the presence and potential growth of organohalide respiring (OHR) bacteria. In this study, the aim was to assess the potential organohalide respiration capacity in wastewater biosolids by investigating actively organohalide respiring bacteria with a focus on organohalide respiration of PCBs and PCE. The results of the biosolids analysis showed increased amounts of products from PCB respiration. Simultaneously, experiments with organohalide respiration of PCE in biosolids samples showed significant decreases PCE concentration after 46 days (28-92%). Subsequently, it was evaluated if the OHR microbial populations in biosolids were similar to those present in intestinal human biofilms by applying a bioinformatic approach. The OHR populations of the communities were analyzed from existing American and Chinese human intestinal microbiomes. The overall groups Proteobacteria, Bacteroides, Actinobacteria, and Firmicutes phyla dominated the microbiomes in all datasets. The OHR groups in biosolids and intestinal biofilms included Dehalogenimonas, Dehalobacter, Desulfitibacter, Desulfovibrio, Sulfurospirillum, Clostridium, and Comamonas. The results of this study showed that several OHR phyla were present in all samples independent of origin. Wastewater and intestinal microbiomes also contained OHR phyla. Overall, the results points towards using bacterial communities in biosolids as indicators of organohalide respiration in wastewater and intestinal microbiomes, which is related to ingestion or halogenated compounds.