Fungi are not involved in biofilm formation on rock wall in subterranean arsenic mine in Poland
Chlebicki, Andrzej; Zielenkiewicz, Urszula; Wilczek, Anna M.
Seven species of fungi were isolated from bacterial biofilms growing on a rock wall in an arsenic mine, namely: Cephalotrichum stemonitis, Coemansia aciculifera, Geomyces pannorum, Mortierella elongata, Mortierella dichotoma, Oidiodendron truncatum, and Trichoderma viridescens. Mycelia of these fungi were not growing in biofilm polymer matrix (EPS) in natural conditions; however, fungal propagules were found to be viable and irregularly distributed in the biofilm. Three species of airborne fungi – Cladosporium herbarum, Alternaria alternata and Exophiala sideris – were isolated from air near the biofilms but were not recovered from within the biofilm. Geomyces pannorum grows on living biofilm under experimental conditions. E. sideris, G. pannorum and C. stemonitis exhibited very limited growth on dead, autoclaved biofilm. EPS appear to be a barrier to penetration of living biofilm by mycelial hyphae in natural conditions. Lack of available hydrocarbons in EPS provides important biofilm protection against colonization by fungi. Evidence presented here suggests that biofilm bacteria produced antifungal compounds inhibiting the growth of mycelia of these fungi as well as other compounds stimulating development of conidiomata. Growth of synnemata of C. stemonitis and conidiophores of Oidiodendron truncatum was stimulated by solutions of some of these excreted substances. Propagation of E. sideris by air was observed.