Characterization of methyl tert-butyl ether-degrading bacteria from a gasoline-contaminated aquifer

Abstract

Molecular microbial community analysis was combined with traditional cultivation strategies to investigate the presence of methyl tert-butyl ether (MTBE)-degrading bacteria in a gasoline-contaminated aquifer (Ronan, MT). A bacterial consortium, RS24, which is capable of complete mineralization of MTBE as a sole carbon and energy source was enriched from soil and aquifer materials taken from the contaminated site. The consortium was capable of degrading MTBE at rates up to 0.66 mg d-,1 with corresponding gross biomass yields of 0.25 ± 0.02 mg dry biomass (mg MTBE)-1. Two MTBE-degrading isolates identified as Pseudomonas Ant9 and Rhodococcus koreensis were obtained from the consortium. However, both isolates required the presence of 2-propanol as a cosubstrate for MTBE degradation. Denaturing gradient gel electrophoresis (DGGE) of Polymerase Chain Reaction (PCR)-amplified 16S rDNA confirmed the presence of both isolates in the initial consortium and indicated their disappearance with transfer and subculturing. MTBE degradation and cell growth by the consortium was stimulated by the presence of spent culture medium, suggesting the production of a growth factor during MTBE degradation. These results indicate the presence of naturally occurring MTBE-degrading bacteria in a contaminated aquifer and suggest the potential for natural attenuation or enhanced aerobic oxidation.