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Mediaeval stained glass has been treated with Polymethylmetacrylate coatings by Kwiatkowski in Poland during the 1950th. Such treated panels were found in the Johannis Church of Toruń (without protective glazing), in the Cathedral of Włocławek (behind a protective glazing), and on glass kept in exhibition cases in the museum of Toruń. Surface coatings have been detected and analyzed. There was no extensive contamination by fungi or bacteria if the glass was either coated or not.
Black ascomycetous microcolonial fungi (MCF) are persistent inhabitants of rock surfaces in deserts as well as ubiquitous in other wide-spread terrestrial ecosystems including man-made materials such as solar panels. The ability of MCF to cope with multiple, rapidly fluctuating stresses makes the group an interesting subject in the study of stress resistance. Carotenoids and melanin are amongst the protective pigments that contribute to the robustness of MCF. We studied their role in stress resistance of the non-pathogenic rock-inhabiting fungus Knufia petricola (Chaetothyriales) strain A95. Disruption of melanin synthesis affects not only oxidative-stress resistance but also the extracellular polysaccharide (EPS) matrix and lipid composition of the cell membrane.
Black ascomycetous microcolonial fungi (MCF) are persistent inhabitants of rock surfaces in deserts as well as ubiquitous in other wide-spread terrestrial ecosystems including man-made materials such as solar panels. The ability of MCF to cope with multiple, rapidly fluctuating stresses makes the group an interesting subject in the study of stress resistance. Carotenoids and melanin are amongst the protective pigments that contribute to the robustness of MCF. We studied their role in stress resistance of the non-pathogenic rock-inhabiting fungus Knufia petricola (Chaetothyriales) strain A95. Disruption of melanin synthesis affects not only oxidative-stress resistance but also the extracellular polysaccharide (EPS) matrix and lipid composition of the cell membrane.
Territories of rock-inhabiting fungi: Survival on and alteration of solid air-exposed surfaces
(2018)
Subaerial biofilms that are omnipresent at the interface between all solid substrates and the atmosphere are composed of a unique and widespread group of ascomycetes called rock-inhabiting fungi or microcolonial fungi (MCF), typically in communities with other microorganisms. While subaerial biofilms in toto have important roles in mineral weathering and biodeterioration of materials, methodological approaches to subaerial biofilm communities are diverse and frequently focussed on MCF. Here, we review the historical development of the research methods applied in the field and consider perspectives to increase our understanding of the biofilm-induced changes of solid substrate surfaces.
Soil formation on rock surfaces is intrinsically coupled to primary microbial colonisation of the atmosphere-lithosphere interface. Rock-inhabiting microbial life is ubiquitous but the mechanisms of biofilm establishment and more importantly, quantification of its geological input are so far only possible to be studied in simplified, well-controlled laboratory experiments. In a previous study [1] a laboratory biofilm consisting of the phototrophic cyanobacterium Nostoc punctiforme ATCC 29133 and the rock-inhabiting ascomycete Knufia petricola A95 was tested for its mineral weathering potential. Mineral dissolution was enhanced in biotic experiments as compared to abiotic ones. Here the influence of K. petricola strain A95 and a recently constructed melanin deficient mutant (A95ΔPKS) were used to study the influence of fungal pigments on weathering of forsteritic olivine. The olivine with fungal biomass was submerged in a nutrient solution (pH 6.2) in batch-reactor flasks that were incubated for 90 d at 25°C and 90 μmol photons.m2.sec-1, while shaken at 150 rpm. qPCR was used to quantify the growth of fungi. Mineral dissolution was quantified by ICP-OES analysis of the liquid medium while SEM-EDX analysis of the solid phase was used to determine secondary mineral formation and visualise growth behaviour. Wild type and mutant accelerated dissolution of the mineral: over time both release more Mg and Si from olivine than the abiotic control. Also SEM revealed a closer physical contact of the wild type cells to the mineral and a higher production of EPS of the melanin mutant A95ΔPKS. This important difference in the ability of the wild type strain to adhere to the mineral surface might be crucial in maintaining a biologically modified environment. This biologically engineered habitat serves as a place where mineral dissolution as well as deposition of metabolic products (EPS + pigments) can impact the rock surface. We expect this study to increase the awareness on the impact of microbiology, and more specifically, rock-inhabiting fungi on mineral weathering. [1] Seiffert, F., Bouchez, J., von Blanckenburg, F., and Gorbushina, A. A. (2014). Microbial colonization of bare rocks: laboratory biofilm enhances mineral weathering. Proc. Earth Plan. Sci. 12,123–129.doi: 10.1016/j.proeps.2014.08.042
Fungal pigments such as melanin and carotenoids are distinctive markers of animal and plant pathogenic fungi as well as their environmental relatives. These complex pigments play important roles in pathogenicity and stress tolerance while also being useful as biomarkers. Accordingly, it is important to be able to identify in situ the pigments in black fungi, a group of clinical and environmental importance. In this study, wild-type and genetically modified strains of Knufia petricola A95 and wild fungal cells attached to ancient rock were investigated for their spectroscopic and microscopic Raman features and morphological appearance. Knockout mutants of melanin synthesis genes pks1 (polyketide synthase), sdh1 (scytalone dehydratase), and both pks1 and the carotenoid synthesis gene phd1 (phytoene desaturase) were studied We applied two different Raman microscopes using two lasers, with 633 nm and 488 nm wavelengths. We analyzed and compared Raman spectra between the measured reference substances and the mutant and wild-type strains. In the wild strain WT:A95, the peaks close to melanin peals were found at 1353 cm−1 and 1611 cm−1. There are no characteristic melanin peaks at 1580–1600 cm−1 and around 1350 cm−1 at the spectrum of the Δpks1/Δphd1 mutant and the Δsdh1 mutant. The Δpks1 mutant spectrum has the peaks at the beta-carotene v2 C-C in-plane stretch at 1155 cm−1 and v3 C-CH3 deformation at 1005 cm−1. The peaks of carotenoids and melanin were found in all mutants and the wild strain, except the Δpks1/Δphd1 mutant. Raman spectra allow for discrimination between the various pigments. Hence, interactions between natural fungal melanin, as well as other protective pigments, and complex environmental matrices can be characterized on a range of spatial and temporal scales.