Metabolite Profile of the Micromycete Lecanicillium gracile Isolated from Plaster and Limestone

Lecanicillium gracile is a recently described micromycete species isolated from mineral-based building materials (plaster and limestone) in interiors of cultural heritage sites in Russia. In this work, the composition of L. gracile metabolites, as well as of the culture liquid, have been characterized. The results suggest that L. gracile is a promising candidate for the search for novel biologically active compounds. During the exponential growth phase, the diversity of metabolites in the mycelium was low; the metabolome profile demonstrated predominant accumulation of monosaccharides and polyols. In the stationary phase, the metabolite diversity in the L. gracile mycelium was high; apparently, at this stage biosynthesis dominated over energy-producing processes. L. gracile synthesized extracellular polymer compounds and shifted medium рН to the alkaline range. When fungi are developing on rock substrates, their extracellular polymer matrix not only serves to facilitate the formation of biofilms with other microorganisms of lithobiont communities, but also, at alkaline pH values, it promotes the formation of secondary calcite on calcium-containing substrates, such as limestone and marble. That is, L. gracile possesses certain biochemical traits that facilitate its long-term growth on rock substrates and reflect the specific character of interactions between the fungus and the substrate materials.