| Pollution by petroleum products is widespread in the environment. Leaking underground storage tanks at service stations are major sources to soil and groundwater of gasoline components such as benzene, toluene, xylene and ethyl-benzene (BTEX). More recently, the fuel oxygenate, methyl-tert butyl ether (MTBE) has emerged as a ubiquitous contaminant of groundwater. The objectives of this study were to: (i) identify and monitor subpopulation(s) involved in intrinsic biodegradation of toluene in soil; (ii) isolate, characterize and determine the potential for bioremediation of a novel MTBE-degrading bacterium; Phopholipid fatty acid (PLFA) analysis of a soil microbial community was coupled with 13C isotope tracer analysis to identify which members of soil community were involved in toluene metabolism. After toluene degradation, 96% of incorporated 13C were detected in 16 of 59 total PLFAs (27%) extracted from whole soil. Of these enriched PLFAs, 85% were identical to the PLFAs of a toluene-metabolizing Rhodococcus sp. isolated from that soil. In contrast, when labeled glucose was added, most soil PLFAs (91%) became labeled, suggesting involvement of multiple populations.; A bacterial strain, PM1, able to aerobically utilize MTBE as its sole carbon and energy source, was isolated from a microbial consortium in a compost biofilter treating MTBE. Initial MTBE degradation rates by 2 × 10 6 cells ml−1 were 0.07, 1.17, and 3.56 μg ml−1 h−1 for initial concentrations of 5, 50, and 500 μg MTBE ml−1 respectively. Strain PM1 converted 46% of radiolabeled MTBE to 14CO2 and 19% to 14C-labeled cells within 120h. Strain PM1 is one of the first bacterial cultures reported to be capable of rapid and complete removal of MTBE as a sole carbon and energy source.; Strain PM1 was inoculated into sediment core material from a contaminated groundwater plume at Port Hueneme, California. Strain PM1 rapidly degraded MTBE concentrations up to 200 μg ml−1. MTBE removal rates were dependent upon oxygen concentration. Nutrient additions had little effect MTBE biodegradation except at very high concentrations (>200 μg MTBE ml−1). These results suggest that Strain PM1 shows promise for use in bioaugmentation applications if sufficient oxygen is provided. |
