Fungal and bacterial biodeterioration of outdoor canvas paintings: the case of the cloisters of Quito, Ecuador

The historic center of Quito, Ecuador, was one of the first World Cultural Heritage Sites declared by UNESCO in 1978. There are numerous religious buildings built during the Spanish colonial period reflecting the cultural heritage in this area. Between them, the cloisters of San Francisco, Santo Domingo, and Santa Clara should be highlighted. The specific problems of conservation of the outdoor canvas paintings are not well known at the moment. The objective of this paper is to achieve a conservation study of the canvas paintings exhibited in these three cloisters of the historic center of Quito in order to identify the microbial agents and the main bioclimatic parameters of deterioration. For this, a study of the state of conservation of five canvas paintings has been carried out, as well as a sampling and identification of the main microorganisms present on the obverse and reverse of the works, employing diverse techniques, traditional and biomolecular ones. An analysis of climatic conditions has also been achieved in the cloister of San Francisco. The results of the study indicate that the exhibition conditions in the cloisters are really problematic for the conservation of paintings. Important biodeteriorating agents have been isolated, including fungi and bacteria species belonging, among others, to the genera Bacillus, Penicillium, Alternaria, Mucor, and Aspergillus. We have also researched its relationship with the deterioration state of the artworks and the exhibition conditions in each case, proposing guidelines for the proper conservation of this important World Cultural Heritage.