Ricerc@Sapienza

Mural paintings in the hypogeal environment of the Tomba degli Scudi in Tarquinia, Italy, show a quite
dramatic condition: the plaster mortar lost his cohesion and a white layer coating is spread over almost
all the wall surfaces. The aim of this research is to verify if the activity of microorganisms could be one of
the main causes of deterioration and if the adopted countermeasures (conventional biocide treatments)
are sufficient to stop it. A biocide treatment of the whole environment has been carried out before the
conservative intervention and the tomb has been closed for one month. When the tomb was opened
again, we sampled the microorganisms present on the frescoes and we identified four Bacillus species
and one mould survived to the biocide treatment. These organisms are able to produce spores, a highly
resistant biological form, which has permitted the survival despite the biocide treatment. We show
that these Bacillus strains are able to produce calcium carbonate and could be responsible for the white
deposition that was damaging and covering the entire surface of the frescoes. Our results confirm that
the sanitation intervention is non always resolutive and could even be deleterious in selecting harmful
microbial communities.