Deteriogenic cyanobacteria on historic buildings in Brazil detected by culture and molecular techniques

There are few modern analyses of the cyanobacterial communities in biofilms on external building surfaces. As the classification of cyanobacteria is rapidly changing, we aimed to identify them on historic buildings in Brazil using both established and molecular techniques. In mature biofilms, cyanobacteria of subsections I and II were generally the major biomass; occasionally filamentous genera of the Scytonemataceae, Microchaetaceae and Rivularaceae were dominant. Filamentous organisms of subsections III and IV were more frequently isolated in culture. PCR products using cyanobacteria-specific 16S rDNA primers were sequenced from morphologically identified organisms. Homologies with deposited sequences were generally low. Phylogenetic analysis showed that many isolates were distant from their nearest neighbours, even though they grouped with their appropriate taxa. The majority of cyanobacterial DNA sequences deposited in data banks are aquatic; our results indicate that cyanobacteria from external walls are an ecologically isolated group.