Isolation and Identification of Biphenyl and Polychlorinated Biphenyl Degrading Microbes

The San Jacinto River system south of the I-10 overpass is heavily contaminated with biphenyl and polychlorinated biphenyls (PCBs), carcinogenic aromatic hydrocarbons that have a deleterious impact on the environment. While typically recalcitrant to most forms of environmental degradation, biphenyl and PCBs compounds are known to share a common microbial degradation pathway with other chlorinated aromatics such as polychlorinated dioxin (PCDD) and dibenzofuran (PCDF). As such the purpose of this research is to isolate and test bacterial strains collected from contaminated San Jacinto River sediment and soil for the capacity to degrade or fully metabolize biphenyl and its derivatives. As conventional clean-up is expensive, such strains can be used in the field of bioremediation as a more cost-effective way of treating environmental contamination. The samples were screened for six weeks in minimal media with putative positive samples isolated for further bioinformatics analysis. Microorganisms identified as Pseudomonas pseudoalcaligenes, Pseudomonas nitroreducens, and Comamonas sp. were noted to harbor a putative 2,3 biphenyl dioxygenase enzyme and were further assessed for possible degradative capacity through a combination of growth kinetics and GC-MS analysis to determine the quality and quantity of the intermediate metabolites. Sample growth results suggest that each of the three isolated study strains are unable to utilize biphenyl or 3-chlorobiphenyl as a sole carbon source. In addition, expected metabolites of biphenyl degradation were not observed in either the supernatant or cell lysate indicating that expression of these putative 2,3 biphenyl dioxygenase enzymes and/or their catalytic activity against biphenyl is likely to be minimal.