Contrary to some previous reports, methyl tertiary-butyl ether (MTBE) can be biodegraded. We have isolated two bacterial strains, PM1 and YM1, which are can use MTBE as their only source of carbon and energy. These strains were obtained from a mixed microbial consortium provided by the University of California, Davis Department of Civil and Environmental Engineering. MTBE degradation by PM1 is rapid (complete disappearance of the pollutant within 4 days), and is not affected by the addition of small amounts of nutrients. YM1 degrades MTBE more slowly (50% degraded in 4 days) and nutrients appear to enhance MTBE degradation. Examination of whole cell lipid profiles for PM1 and YM1 indicates that they are not identical strains. Thermal gradient gel electrophoresis (TGGE) analysis of 16S rRNA gene fragments from the two strains, however, showed no difference between them. 16S rDNA sequence analysis of strains PM1 and YM1 revealed that they are both most closely related to the genus Sphingomonas.

In addition to describing of the MTBE-degrading isolates, we have begun to examine their importance in the MTBE-degrading mixed culture. Fingerprinting methods that analyze cell components (e.g. phospholipids, DNA) extracted directly from mixed cultures and environmental samples can provide insight into the composition and stability of microbial communities. Analysis of DNA by TGGE indicated that neither of the bacterial isolates described above made up dominant bands in the MTBE-grown microbial consortium. An additional unidentified band was particularly dominant when the consortium was cultured on MTBE. We are currently working to obtain the DNA sequence of this band.