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Appl Environ Microbiol, May 1998, p. 1884-1889, Vol. 64, No. 5
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

Oxidation of Methyl-Substituted Naphthalenes: Pathways in a Versatile Sphingomonas paucimobilis Straindagger

Tapan K. Dutta,1,2,* Sergey A. Selifonov,3,Dagger and Irwin C. Gunsalus2

National Research Council,1 and NHEERL, Gulf Ecology Division, U.S. Environmental Protection Agency,2 Gulf Breeze, Florida 32561 and Biochemistry Department, University of Minnesota, St. Paul, Minnesota 551083

Received 16 September 1997/Accepted 20 January 1998

Aromatic compounds with alkyl substituents are abundant in fossil fuels. These compounds become important environmental sources of soluble toxic products, developmental inhibitors, etc. principally through biological activities. To assess the effect of methyl substitution on the completeness of mineralization and accumulation of pathway products, an isolate from a phenanthrene enrichment culture, Sphingomonas paucimobilis 2322, was used. Washed cell suspensions containing cells grown on 2,6-dimethylnaphthalene in mineral medium were incubated with various mono-, di-, and trimethylnaphthalene isomers, and the products were identified and quantified by gas chromatography and mass spectrometry. The data revealed enzymes with relaxed substrate specificity that initiate metabolism either by methyl group monoxygenation or by ring dioxygenation. Congeners with a methyl group on each ring initially hydroxylate a methyl, and this is followed by conversion to a carboxyl; when there are two methyl groups on a single ring, the first reaction is aryl dioxygenation of the unsubstituted ring. Intermediates are channeled to primary ring fission via dihydrodiols to form methyl-substituted salicylates. Further evidence that there are multiple pathways comes from the fact that both phthalate and (methyl)salicylate are formed from 2-methylnaphthalene.

* Corresponding author. Mailing address: NHEERL, GED, U.S. EPA, 1 Sabine Island Drive, Gulf Breeze, FL 32561. Phone: (850) 934-2497. Fax: (850) 934-9201. E-mail: dutta.tapan{at}epamail.epa.gov/gunny{at}gulf.net.

dagger Contribution 1024 from the NHEERL, Gulf Ecology Division, U.S. Environmental Protection Agency, Gulf Breeze, Fla.

Dagger Present address: Maxygen, Inc., Santa Clara, CA 95051.

Appl Environ Microbiol, May 1998, p. 1884-1889, Vol. 64, No. 5
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.


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