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Applied and Environmental Microbiology, June 2001, p. 2705-2711, Vol. 67, No. 6
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.6.2705-2711.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Pathways for Extracellular Fenton Chemistry in the Brown Rot Basidiomycete Gloeophyllum trabeum

Kenneth A. Jensen Jr.,1 Carl J. Houtman,2 Zachary C. Ryan,1 and Kenneth E. Hammel1,*

Institute for Microbial and Biochemical Technology1 and Fiber Processing and Paper Performance Research Work Unit,2 U.S. Department of Agriculture Forest Products Laboratory, Madison, Wisconsin 53705

Received 20 December 2000/Accepted 14 March 2001

The brown rot fungus Gloeophyllum trabeum uses an extracellular hydroquinone-quinone redox cycle to reduce Fe3+ and produce H2O2. These reactions generate extracellular Fenton reagent, which enables G. trabeum to degrade a wide variety of organic compounds. We found that G. trabeum secreted two quinones, 2,5-dimethoxy-1,4-benzoquinone (2,5-DMBQ) and 4,5-dimethoxy-1,2-benzoquinone (4,5-DMBQ), that underwent iron-dependent redox cycling. Experiments that monitored the iron- and quinone-dependent cleavage of polyethylene glycol by G. trabeum showed that 2,5-DMBQ was more effective than 4,5-DMBQ in supporting extracellular Fenton chemistry. Two factors contributed to this result. First, G. trabeum reduced 2,5-DMBQ to 2,5-dimethoxyhydroquinone (2,5-DMHQ) much more rapidly than it reduced 4,5-DMBQ to 4,5-dimethoxycatechol (4,5-DMC). Second, although both hydroquinones reduced ferric oxalate complexes, the predominant form of Fe3+ in G. trabeum cultures, the 2,5-DMHQ-dependent reaction reduced O2 more rapidly than the 4,5-DMC-dependent reaction. Nevertheless, both hydroquinones probably contribute to the extracellular Fenton chemistry of G. trabeum, because 2,5-DMHQ by itself is an efficient reductant of 4,5-DMBQ.

* Corresponding author. Mailing address: Institute for Microbial and Biochemical Technology, USDA Forest Products Laboratory, One Gifford Pinchot Dr., Madison, WI 53705. Phone: (608) 231-9528. Fax: (608) 231-9262. E-mail: kehammel{at}facstaff.wisc.edu.

Applied and Environmental Microbiology, June 2001, p. 2705-2711, Vol. 67, No. 6
0099-2240/01/$04.00+0   DOI: 10.1128/AEM.67.6.2705-2711.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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