Occurrence of halotolerant/halophilic bacterial communities in deteriorated monuments

The use of traditional microbiological methods provides the isolation of a large number of heterotrophic bacteria on deteriorated monuments. However, the spectrum of isolated bacteria changed when the protocols used in studies of halophilic bacteria were applied to mural paintings, efflorescences or mineral deposits. In fact, enumeration of the heterotrophic viable bacteria indicates that the higher counts were, generally, obtained in media with 10% of salt concentration. Media with magnesium sulphate always yielded higher counts than sodium chloride, particularly in environments where magnesium salts were abundant. The predominance of bacilli communities was remarkable. Four cases, in search of halophilic bacteria, are described.