Biosorption of metal ions by Armillaria rhizomorphs

Armillaria rhizomorphs consist of differentiated hyphae with a melanized outer cortex. Melanin is known to prevent lysis of fungal structures by hydrolytic enzymes and may protect against antagonistic microorganisms. Our studies indicate that melanized rhizomorphs also adsorb high concentrations of cations from the surrounding soil environment. Rhizomorphs of four Armillaria species (A. ostoyae (Romagn.) Herink, A. calvescens Berube & Dessureault, A. gemina Berube & Dessureault, and A. sinapina Berube & Dessureault) collected from Minnesota, New Hampshire, and Oregon had substantially elevated levels of metal ions compared with the soil from which they were collected. With some elements, ions were 50–100 times more concentrated on rhizomorphs than in soil. Concentrations of Al, Zn, Fe, Cu, and Pb on rhizomorphs ranged up to 3440, 1930, 1890, 15, and 680 μg/g, respectively. Energy dispersive X-ray microanalysis showed that metal ions were located only on the outer portions of the rhizomorphs and not concen...