Assessment of microbial communities present in white-painted historic buildings in southern and coastal Portugal

Abstract

Portugal’s architecture reflects a rich history influenced by Roman, Moorish, Neoclassical and Romantic styles, with the 20th century marked by Art Deco and colonial influences. Regional styles vary, with white-painted buildings commonly experiencing color changes due to biofilm forma- tion. Visually striking are the red-colored biological patinascommon in the coastal areas. A survey of 120 historical buildings affected by bio-colonization helps to understand the reasons for the patinas’ growing, which beyond natural factors, is often linked to construction defects. A characterization of four samples utilizes Next-Generation Sequencing (NGS) to identify the microorganisms composing the red biofilm, while the SEM-EDS, FTIR-ATR and XRD techniques provide further insights into the biofilm and substrate features. The comprehensive data of biochemical characterization indicate a wide variety of microorganisms, including bacteria and fungi, some of which exhibit potential as producers of a UV-tolerant red/yellow pigment (carotenoid) responsible for the macroscopic coloration of bio-colonization.