In Vitro Experimental Observations on Fungal Colonization, Metalophagus Behavior, Tunneling, Bioleaching and Bioweathering of Multiple Mineral Substrates

Abstract

This study reports on experimental observations during fungi–mineral substrate interactions. Selected mineral substrates of biotite, muscovite, bauxite, chromite, galena, malachite, manganite, and plagioclase were exposed in vitro to free fungal growth under open conditions. The interaction produced strong biochemical and biomechanical alterations to the mineral substrates. Specifically, reported here is a three-dimensional thigmotropic colonization pattern of the mineral surfaces that suggested a possible pattern of fungal metalophagus behavior. Authigenic secondary mineral biomineralization occurred: Ca- and Mg-Oxalates such as weddellite: CaC2O4·2H2O, whewellite: CaC2O4·H2O, and glushinskite: MgC2O4·2H2O; struvite: (NH4) MgPO4·6H2O; gibbsite: Al(OH)3; and gypsum: CaSO4·2H2O. The bioleached elements included Fe, Pb, S, Cu, and Al, which formed single crystals or aggregates, amorphous layers, amorphous aggregates, and linear forms influenced by the fungal filaments. The fungi bioleached Fe and Al from bauxite and Mn from manganite and deposited the metals as separate mineral species. Gypsum was deposited during the interaction with the manganite substrate, indicating a source of Ca and S either within manganite impurities or within the fungal growth environment. Other biochemical and biomechanical features such as tunneling, strong pitting, exfoliation, dissolution, perforations, and fragmentation of the mineral surfaces were also produced. The results of this study, besides emphasizing the role of fungi in bioweathering and mineral alteration, also show that, to produce these alterations, fungi employ a 3D fungal colonization pattern of mineral surfaces guided by thigmotropic and possible metalophagus behavior.