Jody Jellison, Barry Goodell, Grant Kirker, Sam Zelinka, Walter Shortle, Jonathan Schilling, oseph Jakes

The brown rot fungi are important components of the coniferous northern hemisphere forest ecosystem and are characterized by their ability to colonize and degrade lignocellulosic materials; preferentially metabolizing the hemicellulose and cellulose components and leaving a residue of modified lignin. Multiple aspects of the metabolism and degradative capabilities of these organisms are dependent upon cations, including but not limited to iron, manganese, and calcium. As wood degrades, it is characterized by decreasing pH and increasing concentrations of selected cations. The decay fungi, as they colonize the wood, are able to differentially translocate cations as demonstrated by ICP, and to actively modulate their ionic environment. The base cations are needed for many metabolic functions including membrane stabilization and they also function as enzyme cofactors and electrolytes. Transition metal cation concentrations can be shown to influence the extent of fungal sheath formation, and the activity of a biologically unique iron-based non-enzymatic degradative system in the brown rots. They also affect the expression of selected genes involved in oxalate metabolism. The role of iron in the chelator-mediated Fenton (CMF) system is particularly crucial to the ability of the brown rot fungi to depolymerize lignocellulose. Organisms used in this work include: Serpula lacrymans, Postia placenta,Fomitopsis pinicola and Gloeophyllum trabeum. The role played by transition metals, pH, oxalate production and calcium oxalate crystal formation in brown rot physiology and cell wall breakdown mechanisms is discussed along with the potential ecological significance of cation mobilization and redistribution within the forest floor ecosystem