Assessment of microbial communities affecting Almada Negreiros’ mural paintings at a Maritime Station in Lisbon

Abstract

The mural paintings by Almada Negreiros at Lisbon’s Maritime Station of Rocha do Conde de Óbidos, created in 1949, face deterioration due to environmental exposure and past conservation treatments. In 2022, during an on-site analytical campaign aimed at clarifying the artist’ modus operandi and assessing the condition of the paint layers, some areas showed signs of biocolonization and were sampled for analysis. High-throughput sequencing revealed that the predominant prokaryotic phyla are Proteobacteria, Actinobacteria, Firmicutes, Cyanobacteria, and Bacteroidetes, while the dominant eukaryotic phyla are Ascomycota and Basidiomycota. Key bacterial genera identified include Cellulomonas, Methylobacterium, and Rubrobacter, while relevant fungal genera include Penicillium, Cladosporium, Aspergillus, and Stachybotrys. Scanning Electron Microscopy further confirmed the detrimental effects of fungal hyphae, which cause microcracks and structural weakening in the paint layers and underlying mortar. Organic materials from past restoration treatments or original components contribute to microbial growth, accelerating decay. These findings underscore the need for targeted conservation strategies to mitigate microbial proliferation and preserve the authenticity of these invaluable artworks.