Extensive biofilm covering on sgraffito wall art: a call for proactive monitoring.

Background: The study focuses on a black and white sgraffito decoration attached to a cement exterior wall in Kibbutz Yiftach, Israel. Since its creation in 1971, the artwork has experienced weathering processes, resulting in peeling, flaking, and the development of a microbial layer on the wall art decoration. Before its restoration in 2022, this study was initiated, aiming to address three primary questions: What is the composition of the microbial communities? What is the distribution of these microbial communities throughout the wall, and how do they interact with the substrate materials? Methods: Complementary methods, including mineral analysis, microscopic observations, and molecular techniques, were implemented to answer the study questions. Results: Five main groups of bacteria (e.g., Cyanobacteria, Actinobacteria, Proteobacteria, Bacteroidota, and Chloroflexi), as well as various types of fungi, were revealed. Nevertheless, although the same phyla were detected across samples, each displayed distinct diversity at the order level. Microscopic observations revealed the attachment of microbial components to both the porous plaster and the rough cement. Discussion: The study shows a well-developed microbial coating with a localized colonization pattern, underscoring the need for continued long-term monitoring of both the wall-art materials and their environmental conditions to support data-driven conservation.