Damage to buildings, art objects and other structures

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Eukaryotic protists, and more particularly Eumycota, do not attack only farms and crops. Indeed, they are also capable of degrading houses, monuments, works of art, books… Humans make many objects whose raw material comes from plants. If they are moistened a little, they will become the growing medium for fungi. Books are obviously frequently attacked, but wallpapers, boats, sculptures, furniture and even clothing are too. It is more and more frequent that the walls of our houses are colonized by a procession of molds belonging mainly to the genera Penicillium, Aspergillus and Cladosporium (Figure 108). An estimate from the Office for Indoor Air Quality in 2008 suggests that 15% of French homes have visible fungal contamination. Houses are in fact better and better isolated, which often increases ambient humidity and therefore promotes the development of mycelia. These molds feed either directly on the materials or on additives such as glues. They release volatile organic compounds that promote asthma and other respiratory diseases such as sinusitis. In water leakage accidents, the development of fungi can turn catastrophic. The Basidiomycote Agaricomycotina species Serpula lacrymans causes dry rot to houses and furniture (Figure 380). In a matter of weeks, it can invade beams and frames, leading to the collapse of the building. It forms mycelial cords which allow it to effortlessly cross several meters without wood and can thus invade the entire building! In some at-risk regions, a diagnosis confirming the absence of dry rot is necessary before a building can be sold.

Even in places with very low amounts of nutrients, fungi can grow. For example, the paintings in the Lascaux cave have been covered and greatly altered by eukaryotic protists, although their pigments are inorganic. The first arrivals were algae and cyanobacteria which were probably able to develop thanks to the illuminating light and the carbon dioxide present in the confined air of the cave and brought by the very numerous visitors. Then fungi, mainly the Sordariomycetes Fusarium solani, grew on the decaying algae. After antifungal treatment, new Ascomycota fungi of the genus Ochroconis developed on the corpses of the previous ones! Some fungi are even capable of feeding on hydrocarbon vapor and can therefore grow on the walls of cellars where alcohol ages, but also on roofs like in Cognac, or even in kerosene tanks!

Monuments and statues exposed to the open air are attacked by bacteria but also by various lichens, algae and endolithic fungi which will acidify the stone and cause its disintegration. Some of the erosion of rocks in nature occurs through the same coupled actions of lichens, endolithic fungi, and bacteria. Part of our landscapes has therefore been shaped by the action of microorganisms!

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