An unusual sexual stage in the alkalophilic ascomycete Sodiomyces alkalinus

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.

Lipids and soluble carbohydrates in the mycelium and ascomata of alkaliphilic fungus Sodiomyces alkalinus

Alkaliphilic fungi are fundamentally different from alkalitolerant ones in terms of mechanisms of adaptation. They accumulate trehalose in cytosol and phosphatidic acids (PA) in the membrane lipids, whereas alkalitolerants contain these compounds in low amounts. But it is unclear how the composition of osmolytes and lipids changes during cytodifferentiation. In this article the composition of lipids and soluble cytosol carbohydrates in the mycelium and fruit bodies of the alkaliphilic fungus Sodiomyces alkalinus was studied. In the mycelium, mannitol and trehalose dominated, while in fruit bodies only trehalose was predominant. Phosphatidylcholines (PC), PA and sterols were major membrane lipids of the mycelium, while PC and sterols were predominant in fruit bodies. The degree of fatty acids unsaturation of the main mycelium phospholipids (PC and PA) increased with age, while that of PC did not change regardless of the developmental stage. In young mycelium, storage lipids were represented mainly by free fatty acids, and in mature mycelium and fruit bodies-by triacylglycerols. Fruit bodies contained three times less membrane lipids and twice as many storage lipids as mycelium. Trehalose was the main cytosol carbohydrate in the mycelium and fruit bodies, which confirms its key value for alkaliphily.

Micromycetes as colonizers of mineral building materials in historic monuments and museums

Complex of microfungi colonizing mineral building materials, i.e. limestone and plaster, in interiors of cultural heritage was characterized. Wide-scale investigation was carried out with fourteen objects studied. We have revealed a specific culturable community. We have analyzed role of obtained microfungi in biodeterioraton process on the basis of our tests (pH and water activity preferences, ability to solubilize CaCO₃) and literature data (substrate preferences and enzyme activities). The species most actively developing in mineral materials in indoor environments were Acremonium charticola, Acremonium furcatum, Lecanicillium sp., Parengyodontium album, Purpureocillium lilacinum and Sarocladium kiliense. Considering this fact and their ability to develop successfully at extremely wide range of pH values from slightly acidic to alkaline ones and their high enzymatic activities we conclude that the listed species are of high interest in seeking the cause of biodeterioration. These species can actively develop in materials penetrating for years deep into the substrates and causing their deterioration in conditions of considerably heightened moisture content. In this group, A. charticola and Lecanicillium sp. were able to solubilize CaCO₃.