C. Sorlini et al., RESEARCH ON CHROMATIC ALTERATIONS OF MARBLES FROM THE FOUNTAIN OF VILLA-LITTA (LAINATE, MILAN), International biodeterioration & biodegradation, 33(2), 1994, pp. 153-164
The fountain of Galatea at Villa Litta (Lainate, Milan) showed abundan
t flowerings of black spots accompanied by little red spots on the mar
ble surface. On these altered areas no chemolithotrophic bacteria were
found, although many heterotrophic microorganisms were present. The h
igh number of colonies of Alternaria alternata isolated by black spots
may induce us to believe that this fungal strain is the cause of such
alteration. From the red areas however, in spite of the high number o
f heterotrophic bacteria (10(6) CFU/g marble), only a few red pigmente
d microbial strains classified as Micrococcus roseus, Flavobacterium s
p. and Rhodotorula minuta were isolated. The resonance Raman spectra c
arried out on the red spots showed the absence of carotenoids, whilst
the normal Raman spectra showed the presence of minium (Pb3O4). The le
ad probably derives from the pipes of the fountain. Two biocides, Neo-
Desogen and Cequartyl, were tested by minimum inhibitory concentration
on the isolated microorganisms: R. minuta showed a higher sensitivity
to both biocides compared with A. alternata, whilst M. roseus and Fla
vobacterium sp. showed more sensitivity towards Cequartyl. Three years
after treatment with Neo-Desogen, small black and red spots were foun
d. Microbiological analyses and ATP determination showed a new coloniz
ation of the heterotrophic bacteria (10(6) CFU/g) corresponding to the
red spots, and of Mycetes (10(3) CFU/g) corresponding to the black on
es.