The analysis of microbial communities using molecular techniques has become a common method to describe their components. In this study some building materials were inoculated with a microbial consortium of 14 microorganisms, subjected to alternate wetting/drying cycles for six months, and left to rest for eight years. At the end of the resting period, most members of the consortium were detected by molecular methods, which indicate a remarkable preservation of the DNA, although only one bacterium was able to grow in a culture medium. The experimental approach we carried out indicates that the list of microorganisms obtained from DNA analyses reflects not only the actual composition of the microbial communities, but is also a reflection of the microorganisms that were once active on the building materials. © 2011 Elsevier Ltd.

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