Manganese as a Probe of Fungal Degradation of Wood

INTRODUCTION Transition state metals, such as manganese (Mn) and iron (Fe), have been reported to be involved in fungal degradation of wood (Ellis, 1959; Shortle and Shigo. 1973; Blanchette, 1984; Glenn et al., 1986). Manganese is also involved in the enzymatic degradation of lignin model compounds by the white-rot fungus Phanaerochaete chrysosporium Burds. (Tien and Kirk, 1984; Glenn et al., 1986). Iron is believed to be involved in the oxidative degradation of cellulose by brown-rot fungi (CowlingandBrown, 1969; Koenigs, 1974; Schmidt et al., 1981). Current techniques that are typically used for determining the metal content of decayed wood are time-consuming, laborious. and nonspecific (Hunter and Coleman, 1960). A quicker, more specific technique is needed for detecting metals during the wood decay process. Such a technique could be used (1) to obtain knowledge that could serve as a foundation for the development of new methods to prevent wood decay, and (2) as a diagnostic tool to detect the early stages of decay in living trees and in wood in use. The chemical reactions that involve transition metals during the degradation of wood could change the electronic characteristics of the metals. Although the reactions proposed for iron and manganese in the decay process are different, both involve a one electron transfer step that results in changes in the paramagnetic state of the metals. The paramagnetic state of a metal is characterized by unpaired electrons, i.e. electrons unpaired with an oppositely directed spin of another electron. It is possible that these electronic changes could be exploited to detect the chemical nature of the metals during wood decay.