Fungi in archives, libraries, and museums: a review on paper conservation and human health.

The action of fungi on books, documents, maps, and works of art on paper can result in inestimable cultural losses. Plus, some of the fungi present in paper documents, surfaces and air from archives, libraries and museums are also a threat to human health. This work aims to review the literature on the most important and frequent microfungal populations found in paper-based collections all over the world, and correlate these data with human health risks. A total of 71 studies, dating between 1997 and 2018 were reviewed and organized. From 27 different countries, 207 fungal genera and 580 species were reported. Chaetomium sp. and Fusarium sp. were found to be special contaminants in the air of archives and have been associated with paper biodeterioration. The most common fungi reported (e.g. Penicillium, Aspergillus, and Alternaria species) have an impact on paper conservation but can also cause adverse human health effects. The most frequent fungal species retrieved from discoloured paper materials are discussed in greater detail. Considerations on methods of identification and quantification of fungal contamination are also presented. Finally, the authors acknowledge an urgent need for standardizing research in this area and further studies are proposed.

Biodiversity of cyanobacteria and green algae on monuments in the Mediterranean Basin: an overview.

The presence and deteriorating action of micro-organisms on monuments and stone works of art have received considerable attention in the last few years. Knowledge of the microbial populations living on stone materials is the starting point for successful conservation treatment and control. This paper reviews the literature on cyanobacteria and chlorophyta that cause deterioration of stone cultural heritage (outdoor monuments and stone works of art) in European countries of the Mediterranean Basin. Some 45 case studies from 32 scientific papers published between 1976 and 2009 were analysed. Six lithotypes were considered: marble, limestone, travertine, dolomite, sandstone and granite. A wide range of stone monuments in the Mediterranean Basin support considerable colonization of cyanobacteria and chlorophyta, showing notable biodiversity. About 172 taxa have been described by different authors, including 37 genera of cyanobacteria and 48 genera of chlorophyta. The most widespread and commonly reported taxa on the stone cultural heritage in the Mediterranean Basin are, among cyanobacteria, Gloeocapsa, Phormidium and Chroococcus and, among chlorophyta, Chlorella, Stichococcus and Chlorococcum. The results suggest that cyanobacteria and chlorophyta colonize a wide variety of substrata and that this is related primarily to the physical characteristics of the stone surface, microclimate and environmental conditions and secondarily to the lithotype.

Reproducing stone monument photosynthetic-based colonization under laboratory conditions.

In order to understand the biodeterioration process occurring on stone monuments, we analyzed the microbial communities involved in these processes and studied their ability to colonize stones under controlled laboratory experiments. In this study, a natural green biofilm from a limestone monument was cultivated, inoculated on stone probes of the same lithotype and incubated in a laboratory chamber. This incubation system, which exposes stone samples to intermittently sprinkling water, allowed the development of photosynthetic biofilms similar to those occurring on stone monuments. Denaturing gradient gel electrophoresis (DGGE) analysis was used to evaluate the major microbial components of the laboratory biofilms. Cyanobacteria, green microalgae, bacteria and fungi were identified by DNA-based molecular analysis targeting the 16S and 18S ribosomal RNA genes. The natural green biofilm was mainly composed by the Chlorophyta Chlorella, Stichococcus, and Trebouxia, and by Cyanobacteria belonging to the genera Leptolyngbya and Pleurocapsa. A number of bacteria belonging to Alphaproteobacteria, Bacteroidetes and Verrucomicrobia were identified, as well as fungi from the Ascomycota. The laboratory colonization experiment on stone probes showed a colonization pattern similar to that occurring on stone monuments. The methodology described in this paper allowed to reproduce a colonization equivalent to the natural biodeteriorating process.