Pathway, inhibition and regulation of methyl tertiary butyl ether oxidation in a filamentous fungus, Graphium sp.
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The filamentous fungus Graphium sp. (ATCC 58400) co-metabolically oxidizes the gasoline oxygenate methyl tertiary butyl ether (MTBE) after growth on gaseous n-alkanes. In this study, the enzymology and regulation of MTBE oxidation by propane-grown mycelia of Graphium sp. were further investigated and defined. The trends observed during MTBE oxidation closely resembled those described for propane-grown cells of the bacterium Mycobacterium vaccae JOB5. Propane-grown mycelia initially oxidized the majority (∼95%) of MTBE to tertiary butyl formate (TBF), and this ester was biotically hydrolyzed to tertiary butyl alcohol (TBA). However, unlike M. vaccae JOB5, our results collectively suggest that propane-grown mycelia only have a limited capacity to degrade TBA. None of the products of MTBE exerted a physiologically relevant regulatory effect on the rate of MTBE or propane oxidation, and no significant effect of TBA was observed on the rate of TBF hydrolysis. Together, these results suggest that the regulatory effects of MTBE oxidation intermediates proposed for MTBE-degrading organisms such as Mycobacterium austroafricanum are not universally relevant mechanisms for MTBE-degrading organisms. The results of this study are discussed in terms of their impact on our understanding of the diversity of aerobic MTBE-degrading organisms and pathways and enzymes involved in these processes.
KeywordsMethyl tertiary butyl alcohol Cometabolism Graphium sp. Tertiary butyl alcohol Tertiary butyl formate Alkane monooxygenase
- Hanson JR, Ackerman CE, Scow KM (1999) Biodegradation of methyl tert-butyl ether by a bacterial pure culture. Appl Environ Microbiol 65:4788–4792Google Scholar
- Hardison LK, Curry SS, Ciuffetti LM, Hyman MR (1997) Metabolism of diethyl ether and cometabolism of methyl tert-butyl ether by a filamentous fungus, Graphium sp. Appl Environ Microbiol 63:3059–3067Google Scholar
- Hyman MR, Taylor CD, O’Reilly KT (2000) Cometabolic degradation of MTBE by iso-alkane-utilizing bacteria from gasoline-impacted soils. In: Wickramanayake GB, Gavaskar AR, Alleman BC, Magar VS (eds) Bioremediation and phytoremediation of chlorinated and recalcitrant compounds. Battelle Press, Columbus, OH, pp 149–155Google Scholar
- Hyman MR, Smith CA, O’Reilly KT (2001) Cometabolism of MTBE by an aromatic hydrocarbon-oxidizing bacterium. In: Magar VS, Gibbs JT, O’Reilly KT, Hyman MR, Leeson A (eds) Bioremediation of MTBE, alcohols, and ethers. Battelle Press, Columbus, OH, pp 145–152Google Scholar
- Steffan RJ, McClay K, Vainberg S, Condee CW, Zhang D (1997) Biodegradation of the gasoline oxygenates methyl tert-butyl ether, ethyl tert-butyl ether, and tert-amyl methyl ether by propane-oxidizing bacteria. Appl Environ Microbiol 63:4216–4222Google Scholar
- US Environmental Protection Agency (1997) Drinking water advisory: consumer acceptability advice and health effects analysis on methyl tertiary-butyl ether (MtBE). US Environmental Protection Agency.Health and Ecological Criteria Division, Office of Water, Washington, DCGoogle Scholar