Recent studies on the microorganisms involved in biodeterioration are revealing the existence of highly diverse and complex microbial communities. The results obtained during our studies showed the presence of numerous microorganisms never or rarely reported before in caves with rock art paintings. Among these microbial groups, the presence of sulfate-reducing bacteria (mainly belonging to the Deltaproteobacteria), Bacteroidetes, Chloroflexi, Crenarchaeota, Gemmatimonadetes, Nitrospirae, Planetomycetes, Verrucomicrobia, and several uncultured bacterial candidate divisions have been frequently detected. The metabolic capabilities of the microorganisms that have not been previously cultured are generally unknown, and most of the microbial groups mentioned above have never, or rarely, been Cultured. Consequently, there is no information on their potential role oil the deterioration of the studied paintings is unknown.