Microbiological Analysis of Surfaces of Leonardo Da Vinci's Atlantic Codex: Biodeterioration Risk

Bacterial Diversity on Historical Audio-Visual Materials and in the Atmosphere of Czech Depositories

Microbial contamination in cultural heritage storage facilities is undoubtedly still a huge problem and leads to the biodeterioration of historical objects and thus the loss of information for future generations. Most studies focus on fungi that colonize materials, which are the primary agents of biodeterioration. However, bacteria also play crucial roles in this process. Therefore, this study focuses on identifying bacteria that colonize audio-visual materials and those present in the air in the archives of the Czech Republic. For our purposes, the Illumina MiSeq amplicon sequencing method was used. Using this method, 18 bacterial genera with an abundance of higher than 1% were identified on audio-visual materials and in the air. We also evaluated some factors that were assumed to possibly influence the composition of bacterial communities on audio-visual materials, of which locality was shown to be significant. Locality also explained most of the variability in bacterial community structure. Furthermore, an association between genera colonizing materials and genera present in the air was demonstrated, and indicator genera were evaluated for each locality. IMPORTANCE The existing literature on microbial contamination of audio-visual materials has predominantly used culture-based methods to evaluate contamination and has overlooked the potential impact of environmental factors and material composition on microbial communities. Furthermore, previous studies have mainly focused on contamination by microscopic fungi, neglecting other potentially harmful microorganisms. To address these gaps in knowledge, our study is the first to provide a comprehensive analysis of bacterial communities present on historical audio-visual materials. Our statistical analyses demonstrate the critical importance of including air analysis in such studies, as airborne microorganisms can significantly contribute to the contamination of these materials. The insights gained from this study are not only valuable in developing effective preventive measures to mitigate contamination but also valuable in identifying targeted disinfection methods for specific types of microorganisms. Overall, our findings highlight the need for a more holistic approach to understanding microbial contamination in cultural heritage materials.

Imaging and micro-invasive analyses of black stains on the passepartout of Codex Atlanticus Folio 843 by Leonardo da Vinci

This paper accounts for the diagnostic campaign aimed at understanding the phenomenon of black stains appeared on the passepartout close to the margins of Folio 843 of Leonardo da Vinci's Codex Atlanticus. Previous studies excluded microbiological deterioration processes. The study is based on a multi-analytical approach, including non-invasive imaging measurements of the folio, micro-imaging and synchrotron spectroscopy investigations of passepartout fragments at different magnifications and spectral ranges. Photoluminescence hyperspectral and lifetime imaging highlighted that black stains are not composed of fluorescent materials. μATR-FTIR imaging of fragments from the passepartout revealed the presence of a mixture of starch and PVAc glues localized only in the stained areas close to the margin of the folio. FE-SEM observations showed that the dark stains are localized inside cavities formed among cellulose fibers, where an accumulation of inorganic roundish particles (∅100-200 nm in diameter size), composed of Hg and S, was detected. Finally, by employing synchrotron μXRF, μXANES and HR-XRD analyses it was possible to identify these particles as metacinnabar (β-HgS). Further research is needed to assess the chemical process leading to the metacinnabar formation in the controlled conservation condition of Leonardo's Codex.

The Microbiome of Leonardo da Vinci's Drawings: A Bio-Archive of Their History

Seven emblematic Leonardo da Vinci’s drawings were investigated through third generation sequencing technology (Nanopore). In addition, SEM analyses were carried out to acquire photographic documentation and to infer the nature of the micro-objects removed from the surface of the drawings. The Nanopore generated microbiomes can be used as a “bio-archive” of the drawings, offering a kind of fingerprint for current and future biological comparisons. This information might help to create a biological catalog of the drawings (cataloging), a microbiome-fingerprint for each single analyzed drawing, as a reference dataset for future studies (monitoring) and last but not least a bio-archive of the history of each single object (added value). Results showed a relatively high contamination with human DNA and a surprising dominance of bacteria over fungi. However, it was possible to identify typical bacteria of the human microbiome, which are mere contaminants introduced by handling of the drawings as well as other microorganisms that seem to have been introduced through vectors, such as insects and their droppings, visible through the SEM analyses. All drawings showed very specific bio-archives, but a core microbiome of bacteria and fungi that are repeatedly found in this type of material as true degraders were identified, such as members of the phyla Proteobacteria, Actinobacteria, and Firmicutes among bacteria, and fungi belonging to the classes Sordariomycetes and Eurotiomycetes. In addition, some similarities were observed that could be influenced by their geographical location (Rome or Turin), indicating the influence of this factor and denoting the importance of environmental and storage conditions on the specific microbiomes.

Assessment of Bacterial Contamination of Air at the Museum of King John III’s Palace at Wilanow (Warsaw, Poland): Selection of an Optimal Growth Medium for Analyzing Airborne Bacteria Diversity

There is no standardized protocol for the assessment of microbial air contamination in museums and other cultural heritage sites. Therefore, most museums conduct such assessments based on their own guidelines or good practices. Usually, microbial air contamination is assessed using only classical microbiology methods with the application of a single growth medium. Therefore, this medium should be carefully selected to limit any selective cultivation bias. Metabarcoding, i.e., a next-generation sequencing (NGS)-based method, combined with classical microbiological culturing was used to assess the effectiveness of various media applications in microbiological screening at the Museum of King John III’s Palace at Wilanow (Warsaw, Poland). The obtained results indicated that when using a classical microbiology approach to assess the microbial air contamination at the museum, the selection of a proper growth medium was critical. It was shown that the use of rich media (commonly applied by museum conservators) introduced significant bias by severely underreporting putative human pathogens and the bacterial species involved in biodeterioration. Therefore, we recommend the use of other media, such as Frazier or Reasoner’s 2A (R2A) medium, as they could yield more diverse communities and recovered the highest number of genera containing human pathogens, which may be suitable for public health assessments.