Monitoring the colonization of monuments by bacteria: cultivation versus molecular methods.

Building materials commonly used in wall paintings and monuments (mortar, limestone and sandstone) were inoculated with an artificial consortium composed of 14 microorganisms and incubated for 6 months at 28 degrees C. The colonization of the different materials by the consortium was investigated. Culture-independent techniques revealed the presence of a diversity of bacteria, whereas culture-dependent techniques yielded mainly spore-forming bacteria. The data suggest that plating leads to an overestimation of the number of spore-forming bacteria with respect to quiescent vegetative forms; the latter are less easily cultured, but are readily detected by culture-independent techniques.