Bacterial diversity on rock surface of the ruined part of a French historic monument: The Chaalis abbey

The aim of the present study was to analyze the epilithic bacterial diversity of the ruins of the Chaalis Abbey, France. To do this, stone samples were collected at the surface of three areas presenting different macroscopic characteristics: a Discolored Area (DCA), a Damaged Area (DMA) and an Undamaged Area (UDMA). The bacterial diversity investigation after DNA extraction and amplified ribosomal DNA restriction analysis targeting the 16S rRNA genes revealed that clone libraries were dominated by Alphaproteobacteria and Actinobacteria. The main part of recovered phylotypes belonged to genera previously associated with stone colonization and/or biodeterioration. Indeed most abundant Alphaproteobacteria phylotypes belonged to the genus Sphingomonas and to the species Bosea thiooxidans, and most abundant Actinobacteria phylotypes belonged to the genera Rubrobacter and Arthrobacter. Members of Cyanobacteria, Bacteroidetes, TM7, Betaproteobacteria, Deinococcus, Acidobacteria and Chloroflexi were also recovered but to a lesser extent. In conclusion, these results suggest that the ruins of the Chaalis Abbey are covered by bacterial communities mainly composed of Alphaproteobacteria and Actinobacteria able to colonize and, for some of them, to deteriorate stone.