Can bacteria sweep away our mess? New perspectives for cleaning of PCB-contaminated environments

Over the past century humans have introduced a large number of synthetic organic pollutants into the environment with many of them found to be harmful to the ecosystems. The discovery that bacteria are able to convey those chemicals into natural biogeochemical cycles fueled interest in harnessing microbial catabolic capabilities to remediate contaminated environments. Bioremediation, a cost-effective and ecologically friendly method, was proposed as a promising remediation strategy. Development of reliable and efficient strategy requires more understanding of the bacteria involved in the pollutant-degradation processes. Polychlorinated biphenyls are one of the most widely distributed classes of chlorinated pollutants in the environment. Although their production was banned 30 years ago, the destruction of PCBs is of continued relevance due to their persistence, impact on ecosystems and human health concerns. The aim of my work was set on characterizing bacteria as catalysts of PCB-degradation process. Mixed bacterial culture and its metabolically active member, Rhodococcus sp., were enriched from the PCB-contaminated transformer station soil. Laboratory biodegradation experiments suggested that cultures posses substantial PCB-degrading activity. To test their capacity as seed cultures, a small-scale bioremediation assay, involving biostimulation and bioaugmentation strategies, was designed. Results showed that over one-year period 40% of PCBs were removed from the soils. Bioremediation was found to induce shift in a composition and abundance of the functional PCB-degrading and in total microbial community. Combination of molecular approaches with chemical analyses can be of prime interest for monitoring and predicting the efficiency of bioremediation for the removal of pollutants from contaminated sites