Medieval wall paintings—a habitat for archaea: identification of archaea by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified gene fragments coding for 16S rRNA in a medieval wall painting

This report describes the detection and identification of archaea in a deteriorated medieval wall painting from the 13th century by denaturing gradient gel electrophoresis (DGGE) of PCR-amplified DNA encoding 16S rRNA without prior cultivation of the organisms. Total DNA was extracted from wall painting material and 547 bp fragments of the 16S rDNA were amplified with archaeal specific primers. Six out of ten analyzed samples showed the presence of archaeal 16S rDNA fragments. The PCR products of uniform length presumably obtained from different archaea species were separated according to their sequence differences by DGGE to visualize the diversity of the archaeal community within the wall painting material. By sequencing an individual DNA band and comparing the data with known 16S rDNA sequences, the corresponding bacteria were identified as members or close relatives of the genus Halobacterium. The results suggest that archaea and, in particular, extremely halophilic species might be more widely involved in deterioration and discolouration processes than commonly recognized.