Microbial communities on painted wet and dry external surfaces of a historic fortress in Niteroi, Brazil

Bacteria, algae and fungi colonising dry (Fl) and wet (F2) white painted walls in the fortress of Santa Cruz da Barra, Niteroi, Brazil, were detected using field emission-scanning electron microscopy (FE-SEM) and next generation DNA sequencing (NGS) techniques. Major bacterial phyla Operational Taxonomic Units (OTUs) detected were Chloroflexi in the wet green biofilm F2 (38.85% compared with 7.56% in Fl) and Proteobacteria in the dry grey biofilm Fl (57.17% compared with 28.69% in F2). Diatoms were detected at both sites by FE-SEM, but only at Fl by NGS. More algae and cyanobacteria were identified at Fl, and this was the only biofllm containing Archaea, possibly related to the high level of salt efflorescences at this site. Although thinner, Fl biofllm showed considerably higher genus richness than the wet biofilm, F2. The thickness and appearance of the biofilms did not correlate with their genomic complexity. Ascomycetes of the Sordariomycetes were major fungi identified at both sites, Khuskia (333% OTUs) at Fl and Emericellopsis (7.99% OTUs) at F2, and few filamentous forms were seen by microscopy. However, many fungal OTUs could not be identified to phylum level. Potential bacterial and fungal paint deteriogens were detected at both sites. The results confirmed the importance of using a variety of techniques in the study of microbial communities. (C) 2017 Elsevier Ltd. All rights reserved.