Afterwards, all positively detected clones were recultured in LB broth and aliquots were preserved at −80 °C in 99% glycerol in a 1 : 3 mixture (Sambrook & Russel, 2001). Sequencing of clone inserts from clone libraries from building material samples was carried out by Services in Molecular Biology (Berlin) using M13f or M13r sequencing primer (Invitrogen Corp., Carlsbad, CA), resulting in sequence lengths of approximately 400 bp. Similarity searches of all sequences from all clone libraries selleck inhibitor against the NCBI database were carried out using blast search

(http://www.ncbi.nlm.nih.gov/). Multiple sequence alignment with type strains of the detected genera as well as genetic distance calculations (distance options according to the Kimura-2 model; Kimura, 1980) of the data were also performed using the software package mega (Molecular Evolutionary Genetics Analysis) version VE-821 4.0. In addition, SSCP (fingerprinting) was performed to verify the primer system for fingerprint analyses, in order to analyse changes or differences within the actinobacterial community in the environmental samples. In our case, a PCR protocol with the actinobacterial-specific primer system for SSCP was applied to detect a possible correlation of the actinobacterial communities and the different types of building material. PCR was performed as described above using a phosphorylated Ac1186r primer

(Table 2). The preparation of the samples as well as the SSCP-polyacrylamide gel electrophoresis and silver staining was performed according to Thummes et al. (2007). A further cluster analysis of this SSCP fingerprint generated Cell press from the different building material samples was made of a normalized gel with GelCompar® II 4.0 (Applied Maths, Belgium). upgma was used for clustering and the Dice coefficient was chosen as a similarity measure. Actinobacteria-specific primer Ac1186r was tested for its specificity by submission to the Probe Match algorithm of RDP, allowing zero mismatches. In silico testing showed that 99.15% of the matches corresponded to sequences of Actinobacteria. With this primer, nearly 50% of all actinobacterial sequences

currently listed in RDP were matched correctly. Just 0.6% of matches are sequences from nontarget bacteria, and 0.25% of matches are sequences of unclassified bacteria. If the dataset options in the RDP database were restricted to type strains of a size >1200 bp, 88.3% of the actinobacterial sequences would be matched by primer Ac1186r, allowing zero mismatches. In silico testing of 164 different sequences from type strains of 75 different genera shows that all sequence fragments theoretically amplified using the new primer system could be reassigned to the correct genera (data not shown). Optimized primer conditions for the new primer system were investigated by PCR using genomic DNA from 31 Actinobacteria-type strains and 13 non-Actinobacteria strains (Table 1).