[Mechanisms of microbial corrosion on petrous materials].

Present studies related to stone weathering demonstrate that the biological activity of bacteria, algae, fungi and lichens play an important role in the biodegradative processes implied in stone building decay. In natural environments is not possible to separate the damage provoked by microorganisms from damage caused by physical and chemical agents. In vitro assays carried out with microbes isolated from weathered stones are required in order to understand the biological mechanisms involved in stone deterioration. We have demonstrated, by means of different techniques as commented in the text, that filamentous fungi contribute greatly to stone biodeterioration by using different mechanisms: (a) mechanical (hyphae growth and penetration in stony substrate); and (b) biochemical (organic acid excretion, cation release, chelation and deposition of organic salts, precipitation of neoformation salts and metals oxidation).