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Applied and Environmental Microbiology, July 2002, p. 3442-3448, Vol. 68, No. 7
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.7.3442-3448.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Degradation of Humic Acids by the Litter-Decomposing Basidiomycete Collybia dryophila

Kari Timo Steffen,1* Annele Hatakka,1 and Martin Hofrichter2

Department of Applied Chemistry and Microbiology, Division of Microbiology, 00014 University of Helsinki, Helsinki, Finland,,1 Unit of Environmental Biotechnology, International Graduate School Zittau, 02763 Zittau, Germany2

Received 26 December 2001/ Accepted 11 April 2002

The basidiomycete Collybia dryophila K209, which colonizes forest soil, was found to decompose a natural humic acid isolated from pine-forest litter (LHA) and a synthetic 14C-labeled humic acid (14C-HA) prepared from [U-14C]catechol in liquid culture. Degradation resulted in the formation of polar, lower-molecular-mass fulvic acid (FA) and carbon dioxide. HA decomposition was considerably enhanced in the presence of Mn2+ (200 µM), leading to 75% conversion of LHA and 50% mineralization of 14C-HA (compared to 60% and 20%, respectively, in the absence of Mn2+). There was a strong indication that manganese peroxidase (MnP), the production of which was noticeably increased in Mn2+-supplemented cultures, was responsible for this effect. The enzyme was produced as a single protein with a pI of 4.7 and a molecular mass of 44 kDa. During solid-state cultivation, C. dryophila released substantial amounts of water-soluble FA (predominantly of 0.9 kDa molecular mass) from insoluble litter material. The results indicate that basidiomycetes such as C. dryophila which colonize forest litter and soil are involved in humus turnover by their recycling of high-molecular-mass humic substances. Extracellular MnP seems to be a key enzyme in the conversion process.

* Corresponding author. Mailing address: Department of Applied Chemistry and Microbiology, P.O. Box 56, Biocenter 1, Viikinkaari 9, FIN-00014 Helsinki, Finland. Phone: 358 9 191 59321. Fax: 358 9 191 59322. E-mail: kari.steffen{at}helsinki.fi.

Applied and Environmental Microbiology, July 2002, p. 3442-3448, Vol. 68, No. 7
0099-2240/02/$04.00+0     DOI: 10.1128/AEM.68.7.3442-3448.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Qualls, R. G. (2004). Biodegradability of Humic Substances and Other Fractions of Decomposing Leaf Litter. Soil Sci. 68: 1705-1712 [Abstract] [Full Text]  
  • Steffen, K. T., Hatakka, A., Hofrichter, M. (2003). Degradation of Benzo[a]pyrene by the Litter-Decomposing Basidiomycete Stropharia coronilla: Role of Manganese Peroxidase. Appl. Environ. Microbiol. 69: 3957-3964 [Abstract] [Full Text]  


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