THE APPLICATION OF FATTY-ACID METHYL-ESTER ANALYSIS (FAME) FOR THE IDENTIFICATION OF HETEROTROPHIC BACTERIA PRESENT IN DECAYING LEDE-STONE OF THE ST-BAVO-CATHEDRAL IN GHENT

The heterotrophic bacterial community present in decaying Lede-sandstone of the Cathedral of Ghent (Belgium) was studied. Two-hundred thirty-two heterotrophic bacterial strains were isolated of which 162 were studied by fatty acid methyl ester analysis (FAME). One-hundred forty isolates were Gram-positive; 101 strains belong to the genus Micrococcus; nine strains were identified as M. kristinae. One large cluster of 83 strains was related to M. luteus/M. lylae. Other Gram-positive strains were related to Arthrobacter. Of the 22 Gram-negative strains, seven strains were related to Pseudomonas vesicularis. A number of Gram-negative and Gram-positive isolates formed separate clusters which could not be identified. The possible role of the bacterial isolates in stone degradation was examined by a zone-clearing test on a calcite-containing medium. Of the 152 strains examined, only nine showed clearing zones after 7 days of incubation at 25 degrees C, 20 odd strains showed a dissolution of calcite after 14 days, whereas all other strains showed no clearing zones, even after prolonged incubation (up to 3 months). The zone-clearing test showed the same reactions when incubated at 24 degrees C or at 19 degrees C.