Biofilms on church walls in Porto Alegre, RS, Brazil, with special attention to cyanobacteria

The populations of phototrophs in biofilms on the external walls of six churches in Porto Alegre were identified. Cyanobacterial isolates were identified morphologically, according to Bergey, and PCR products were obtained for sequencing using the universal forward primer, 27F1, and the cyanobacteria-specific reverse primer, 408R. The sequences were submitted to the BLAST search analysis. Eleven cyanobacterial taxa were found and among algae three genera predominated. Three of the cyanobacterial taxa were coccoid groups and eight were filamentous. Two orders (Pleurocapsales and Chroococcales) and two filamentous genera (Lyngbya and Scytonema) were present on five of the six buildings. Cyanobacterial genera with reported stone-boring activity which were detected on the churches were Synechocystis, Gloeocapsa, Scytonema and Mastigocladus, as were members of the Order Pleurocapsales. The best-maintained church had the lowest cyanobacterial biodiversity; in damp areas of this church many algae were present in biofilms and none of the cyanobacterial groups mentioned above were detected.