Cyanobacterial diversity and ecology on historic monuments in Latin America.

Cyanobacterial biofilms are complex communities of microorganisms that cause damaging activity on historic monuments. A combined molecular approach shows that cyanobacteria belonging to the order Pleurocapsales are the main colonizers at the Mayan site of Uxmal, Mexico, confirming previous microscopic and culture-based reports. An important, previously unrecognized non-cyanobacterial community comprising Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes has also been found in Uxmal. Cyanobacterial communities in Palenque were composed of over 10 species, mainly coccoid forms. A novel PCR method designed to directly amplify DNA from uncultured cyanobacterial cells on historic buildings in Brazil indicated that the identified cyanobacteria sequenced corresponded to their appropriate morphological groups (as defined by both the bacterial and botanical codes). However, their homologies with deposited sequences were, in general, low. Terrestrial cyanobacteria from stone surfaces in Brazil, again mainly coccoid, formed a distinct population that differed from the better-studied aquatic members. Overall, results here show demonstrate that coccoid cyanobacteria are the main colonizers on Latin American monuments under tropical and subtropical conditions and the assessment of their potential deteriogenic activity requires the further development of rapid molecular techniques. Polyphasic studies are essential to increase our knowledge of the diversity of terrestrial biofilms and of global microbial diversity.