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Abstract Historical paper documents are susceptible to complex degradation processes. Biodeterioration is one of the usual suspects that progressively compromises their aesthetic and structural integrity. This study analyses 17th -century handwritten historical letters stored at the Correr Museum Library in Venice, Italy, exhibiting pronounced signs of biodegradation. The techniques used encompassed traditional colony isolation on agar plates and proteomics analyses, employing nanoscale liquid chromatography coupled with high-resolution mass spectrometry (nano-LC-MS). Additionally, fluorescence microscopy was applied for the first time in the historical paper biodeterioration context to supplement the conventional stereoscopic, optical, and scanning electron microscopic imaging techniques. This method enables the visualisation of microorganisms beyond and beneath the paper’s surface through their natural intrinsic autofluorescence in a non-invasive and non-destructive way. The results demonstrate a diverse, complex, and abundant microbiota composed of coexisting fungal and bacterial species (Ascomycota, Mucoromycota, Basidiomycota, Proteobacteria, and Actinobacteria), along with mite carcasses, insects, parasites, and possibly protists. Additionally, this study reveals certain species that were not previously documented in the biodeterioration of historical paper, including human pathogens, such as Histoplasma capsulatum , Brucella , Candida albicans , and species of Aspergillus (flavus , fumigatus, oryzae, terreus, niger) known to cause infections or produce mycotoxins, posing substantial risk to both artefacts and humans.
Stratigaki et al. (Tue,) studied this question.