ABSTRACT
Microorganisms present in superficial biofilms on the external surfaces of historic buildings include algae, cyanobacteria, heterotrophic bacteria and fungi. The biodiversity seen microscopically in rehydrated biofilms from surfaces is much larger than suggested by standard isolation techniques, indicating that molecular methods of community analysis should be used in conjunction with microscopy to obtain a more realistic view of the terrestrial biofilm communities. Some sequences were found to have good homology with cyanobacterial sequences deposited in data bases, but others showed no good match. Many cyanobacteria and the most prevalent fungi on external surfaces of buildings are darkly pigmented. Micromanipulation for purification of single species may fail to yield viable coccoid cyanobacterial colonies. Many coccoid colonial morphotypes were seen on direct observation of the rehydrated samples. Cyanobacteria identified on historic churches in the Brazilian States of Rio Grande do Sul and Minas Gerais were both filamentous and coccoid colonial types.
