Extremophilic bacteria for bio-cleaning cultural heritage

Biotechnologies applied to cultural heritage are able to combat various artistic pathologies, such as the removal of organic substances, black crusts and mineral salts by using different cultures of viable bacteria (Ranalli et al., 2000a). Microorganisms belonging to genera Pseudomonas has been used for bio-cleaning interventions on the external walls of the cathedral of Matera, Italy and the wall paintings placed in the lunettes of the central vault of the Santo Juanes church in Valentia, Spain (Alfano et al., 2011b; Roig et al., 2013c). For the first time the use of extremophilic bacteria to remove salts efflorescence on surface of stone samples was attempted. With the aim to select the most effective bacteria in bio-remediation processes, thermophiles, halophiles, alkalophiles, haloalkalophiles and psychrophiles microorganisms isolated from marine and volcanic environments were screened. The most promising cleaning activity was shown by species belonging to haloalkalophiles. Importance was simultaneously given to develop easy and rapid methods for both bacteria application and their removal on stone substrata. Moreover, no chromatic alterations were observed by visual inspection on the surface of stone samples after bacteria removal. It is to be pointed out that specific treatments based on extremophilic microorganisms adapted to thrive in ecological niches, that are uninhabitable to others, ensure non-toxicity, eco-sustainability along with safe application and removal processes.