Evaluating degradation of polycyclic aromatic hydrocarbon (PAH) potential by indigenous bacteria isolated from highly contaminated riverbank sediments

The aim of this study was to identify and culture bacteria indigenous from heavily polycyclic aromatic hydrocarbons (PAH)-contaminated sediments and evaluate their degradative potential. Fifteen novel aerobic PAH degraders mostly associated with Stenotrophomonas, Pseudomonas, Brucella, and Achromobacter genera were isolated. MHR3A, related to Brucellamicroti CCM 4915, MHR3B, related to Pseudomonasputida NBRC 14164, and MHRN15A, related to Achromobacterkerstersii LMG 344, grew aggressively on PAHs as sole carbon sources and were used for degradation studies. With no amendment or added surfactant, within 15 days, MHR3B was able to degrade 78%, 82%, and 57%, respectively of fluorene, phenanthrene, and pyrene (FPP) compared to the controls which were statistically lower. MHR3A was able to degrade 81%, 84%, and 73% of FPP respectively, while MHRN15A was able to degrade 18%, 29%, and 20% of FPP. An anaerobic consortium enriched on FPP, consisting mainly of Gammaproteobacteria and Clostridia, was obtained and tested under sulfate-reducing conditions in the presence of anthraquinone-2,6 disulfonate (AQDS); however, FPP loss attributed to bacteria was only 15% over 120 days. This study demonstrated that isolation and culturing techniques coupled with standard molecular methods warrants continued investigation of indigenous microbes for in situ remediation of highly PAH-contaminated environments.