Biodiversity of Geodermatophilaceae isolated from altered stones and monuments in the Mediterranean basin

An investigation was made into the occurrence and biodiversity of Geodermat ophilaceae on 78 samples of altered stone surfaces from 24 monuments and na tural stones in the Mediterranean basin; it was found that the total microb ial counts ranged between 0 and 10(7) cfu g(-1) dry weight. Members of the Geodermatophilaceae family were isolated from 22 of the 78 samples examined , with the incidence of Geodermatophilaceae colonies in the cultivable popu lation ranging from 1% to 100%. The highest percentage was found in six sam ples of markedly deteriorated stone. Sixty-five strains randomly isolated f rom the plates were clustered in six different groups by amplified 16S rDNA restriction analysis (ARDRA) using five different restriction enzymes. Twe nty-five strains, representing all the ARDRA haplotypes, were characterized further by partial sequencing (350-550 bp) of the 16S rDNA and by analysin g 76 morphological, metabolic and physiological properties. The strains wer e associated with three well-separated clusters of the genera Geodermatophi lus, Blastococcus and Modestobacter. On the basis of 16S rDNA sequence and ARDRA analysis, only two strains were found to be related to the two refere nce strains of Geodermatophilus. All the others could be grouped with Blast ococcus aggregatus (19 strains) or the Antarctic species Modestobacter mult iseptatus (44 strains), suggesting that it is these two groups, rather than Geodermatophilus, that tend to colonize the stone surfaces, and that Modes tobacter-like strains are also found in temperate/Mediterranean climates. F rom the BOX-polymerase chain reaction (PCR) data, it can be seen that the M odestobacter-like strains, belonging to the most represented ARDRA haplotyp e (haplotype B, 34 strains), are very polymorphic and that, over a stone su rface, there is a wide genetic diversity at the microsite level.