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Applied and Environmental Microbiology, September 2009, p. 5514-5522, Vol. 75, No. 17
0099-2240/09/$08.00+0     doi:10.1128/AEM.00078-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Metabolism and Cometabolism of Cyclic Ethers by a Filamentous Fungus, a Graphium sp.{triangledown}

Kristin Skinner,1 Lynda Cuiffetti,1 and Michael Hyman2*

Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon 97330,1 Department of Microbiology, North Carolina State University, Raleigh, North Carolina 276952

Received 13 January 2009/ Accepted 23 June 2009

The filamentous fungus Graphium sp. (ATCC 58400) grows on gaseous n-alkanes and diethyl ether. n-Alkane-grown mycelia of this strain also cometabolically oxidize the gasoline oxygenate methyl tert-butyl ether (MTBE). In this study, we characterized the ability of this fungus to metabolize and cometabolize a range of cyclic ethers, including tetrahydrofuran (THF) and 1,4-dioxane (14D). This strain grew on THF and other cyclic ethers, including tetrahydropyran and hexamethylene oxide. However, more vigorous growth was consistently observed on the lactones and terminal diols potentially derived from these ethers. Unlike the case in all previous studies of microbial THF oxidation, a metabolite, {gamma}-butyrolactone, was observed during growth of this fungus on THF. Growth on THF was inhibited by the same n-alkenes and n-alkynes that inhibit growth of this fungus on n-alkanes, while growth on {gamma}-butyrolactone or succinate was unaffected by these inhibitors. Propane and THF also behaved as mutually competitive substrates, and propane-grown mycelia immediately oxidized THF, without a lag phase. Mycelia grown on propane or THF exhibited comparable high levels of hemiacetal-oxidizing activity that generated methyl formate from mixtures of formaldehyde and methanol. Collectively, these observations suggest that THF and n-alkanes may initially be oxidized by the same monooxygenase and that further transformation of THF-derived metabolites involves the activity of one or more alcohol dehydrogenases. Both propane- and THF-grown mycelia also slowly cometabolically oxidized 14D, although unlike THF oxidation, this reaction was not sustainable. Specific rates of THF, 14D, and MTBE degradation were very similar in THF- and propane-grown mycelia.

* Corresponding author. Mailing address: Department of Microbiology, North Carolina State University, 4545 Gardner Hall, Raleigh, NC 27695. Phone: (919) 515-7814. Fax: (919) 515-7867. E-mail: Michael_hyman{at}ncsu.edu

{triangledown} Published ahead of print on 6 July 2009.

Applied and Environmental Microbiology, September 2009, p. 5514-5522, Vol. 75, No. 17
0099-2240/09/$08.00+0     doi:10.1128/AEM.00078-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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