Comparative analyses of the bacterial diversity on two different biodeteriorated wall paintings by DGGE and 16S rDNA sequence analysis

The bacterial diversity associated with two different biodeteriorated wall paintings in Herberstein (Austria) and Greene (Germany) was investigated and compared using a molecular approach combining fingerprinting by DGGE (denaturing gradient gel electrophoresis) with the screening of 16S rDNA clone libraries by DGGE and sequencing. In total, 70 16S rDNA sequences were obtained. Twenty-three sequences were phylogenetically affiliated with genera of the Actinobacteria, namely Arthrobacter, Actinobispora, Amycolata, Asiosporangium, Frankia, Geodermatophilus, Nocardioides, Promicromonospora, Pseudonocardia, Rubrobacter, Streptomonospora, Saccharopolyspora, Sphaerobacter and Thermocrismum. Twenty-seven sequences were affiliated with genera of the Proteobacteria, namely Aquaspirillum, Chromohalobacter, Deleya, Erythrobacter, Halomonas, Porphyrobacter, Pseudomonas, Rhizobium, Salmonella and unidentified γ-Proteobacteria. Nineteen sequences were affiliated with unidentified Cytophagales. One sequence was affiliated with the Chloroflexaceae group. Most genera were present in more than one sample. The bacterial communities present on the two different wall paintings showed only similarities in members of unidentified Cytophagales and of the genera Frankia, Geodermatophilus and Arthrobacter. Cultivation experiments for one sample were carried out in parallel to the molecular approach. Isolates were clustered by FAME (fatty acid methyl ester analysis) and representative members of each cluster were additionally analyzed by DGGE. No similar organisms could be detected by the cultivation approach and the molecular approach. Isolates were phylogenetically affiliated to the genera Bacillus, Paenibacillus, Micrococcus, Staphylococcus, Methylobacterium and Halomonas. The sequence of the isolated Halomonas differed from the Halomonas sequences, which were obtained by the molecular approach. The combined approach of molecular and culturing techniques gives a truer picture of all bacterial organisms on/in a surface than either alone.