Parengyodontium album,a frequently reported fungal species in the cultural heritage environment

Fungi are one of the main agents responsible for the biodeterioration of cultural heritage through physical and chemical processes. The frequent isolation of certain fungal species from deteriorated materials indicates that these species appear to have a particular affinity for environmental conditions occurring in cultural heritage. It is important to identify the conditions that favour the development of such species in order to understand how to preserve monuments and collections. Among these fungal species, the involvement of Parengyodontium album (Limber) Tsang et al. seems to have been underestimated until now. This species is abundant in many environments and its taxonomic position has changed quite frequently, which may have concealed the effect of this fungus on cultural heritage sites. This review seeks to compile the involvement of P. album in cultural heritage biodeterioration phenomena under all the names that it has been attributed in order to effectively determine its occurrence. This paper also aims to determine whether P. album is marginal or dominant when detected on materials. Finally, the conditions that favour the development of P. album on cultural heritage objects and sites are discussed.     

Microbial deterioration of cultural heritage and works of art — tilting at windmills?

Microorganisms (bacteria, archaea and fungi), in addition to lichens and insect pests, cause problems in the conservation of cultural heritage because of their biodeteriorative potential. This holds true for all types of historic artefacts, and even for art made of modern materials, in public buildings, museums and private art collections. The variety of biodeterioration phenomena observed on materials of cultural heritage is determined by several factors, such as the chemical composition and nature of the material itself, the climate and exposure of the object, in addition to the manner and frequency of surface cleaning and housekeeping in museums. This study offers a review of a variety of well-known biodeterioration phenomena observed on different materials, such as stone and building materials, objects exhibited in museums and libraries, as well as human remains and burial-related materials. The decontamination of infected artefacts, exhibition rooms and depots incurs high expenditure for museums. Nevertheless, the question has to be raised: whether the process of biodeterioration of cultural heritage can or should be stopped under all circumstances, or whether we have to accept it as a natural and an implicit consecution of its creation. This study also highlights critically the pros and cons of biocide treatments and gives some prominent examples of successful and unsuccessful conservation treatments. Furthermore, an outlook on the future research needs and developments in this highly interesting field is given.     

Application of molecular techniques for identification of fungal communities colonising paper material

Archives and libraries all over the world suffer from biodeterioration of writings caused by microorganisms, especially fungi. With traditionally used culture-dependent methods, only a small amount of effectively colonising organisms is detected. Restoration and maintenance of written cultural heritage is therefore problematic due to incomplete knowledge of the deterioration agents.In the present study, culture-independent molecular methods were applied to identify fungal communities colonising paper samples of different composition and age. Nucleic-acid-based strategies targeting the internally transcribed spacer (ITS) regions, which are nested in the nuclear rDNA repeats, were selected to investigate the fungal diversity on paper. The ITS regions possess a high variation among taxonomically distinct fungal species and even within the species.With this aim, several molecular biological methods were optimised for working with paper materials. Here, we introduce a DNA extraction protocol, which allowed the direct extraction of PCR-amplifiable DNA from samples derived from different kinds of paper. The DNA extracts were used to amplify either the ITS1 or ITS2 region by using different fungi-specific primer sets. The ITS-amplified regions were subsequently analysed by denaturing gradient gel electrophoresis (DGGE). Conditions for DGGE analysis, gradient, voltage, and running time, were established to accurately discriminate different fungal species in complex communities. Pure fungal strains were used to constitute a marker for further comparative investigations of historic papers.     

Diversity and spatial–temporal distribution of airborne fungi at the world culture heritage site Maijishan Grottoes in China

The deposition of the airborne microorganisms onto cultural heritage is associated closely with the subsequent biodeterioration. In this study, a systematic investigation was carried out to detect the seasonal variation and diversity of airborne fungal concentration at the World Cultural Heritage Site Maijishan Grottoes in western China. A bio-aerosol sampler was deployed to collect samples over four seasons in 2016. The culturable airborne fungi were isolated, purified and then identified with the extraction of genomic DNA, PCR amplification of ITS rRNA region, sequencing, and phylogenetic analysis. The concentrations of culturable fungi ranged from 216 to 1389 CFU/m³, which varied seasonally with significant differences among the sampling sites. Fifteen different fungal genera were confirmed, among them, Cladosporium was the most predominant fungal genus, followed by Penicillium. The fungal community structure and their relationship with environmental factors were also delineated. The spatial–temporal differences of airborne fungi at Maijishan Grottoes were mainly due to height, rainfall, relative humidity, and temperature. The dominant genera Cladosporium and Penicillium may pose potential threats to the ancient painted sculptures and murals, and monitoring of the airborne fungi at such a heritage site could provide supporting data for the pre-warning and control of fungal outbreaks inside the caves for better management.

     

Isoenzyme characterization of proteases and amylases and partial purification of proteases from filamentous fungi causing biodeterioration of industrial paper

Biodeterioration is an undesirable process that can affect cultural heritage and economically important materials. Although several biotic and abiotic conditions can accelerate this process, microorganisms are perhaps its main promoters. Fungi are the most important microbial agents of biodeterioration of industrial paper stored in archives. The high genetic plasticity of these organisms allows them to adapt to different environments, using almost any class of materials as substrate. Fungi produce a wide array of enzymes, including cellulases, amylases, and proteases, which are responsible for their gross biodeterioration activity. Thirty-two morphotypes of filamentous fungi were isolated on different media from industrial paper at an advanced stage of biodeterioration. The isolates showed different degrees of cellulolytic, proteolytic, and amylolytic activities on plate assays. The highest proteolytic and amylolytic activities were selected for isoform characterization, which provided an indication of the biochemical diversity that allowed them to colonize these materials. Eladia sacculum was the morphotype selected for partial purification of basic proteases since it has three basic isoforms, simplifying the purification process. We obtained a protein of 35 kDa with a pI of 8.9.     

Involvement of Streptomyces in the Deterioration of Cultural Heritage Materials Through Biomineralization and Bio-Pigment Production Pathways: A Review

Abstract

Streptomyces are involved in the deterioration of cultural heritage materials through several pathways, the most important of these are biomineralization and bio-pigment production. The biomineralization pathway can occur through the precipitation of calcite, silica, barytes, hydromagnesite and iron compounds on colonized paintings and on stone surfaces with paintings in relief. Streptomyces biomineralize boron although it was confirmed in biodeterioration of cultural heritage materials. The other pathway occurs via bio pigment production and the most common of these biopigments are melanin with colors ranging from black through brown to olive, carotenoids with colors ranging from red, yellow, and pink through to violet and thirdly, actinorhodin-related blue pigments.     

Addressing the microbiological problems of cultural property and archive documents after earthquake and tsunami

An International Symposium on the Conservation and Restoration of Cultural Property with a focus on microbial biodeterioration of cultural property was held in Tokyo, Japan on December 5–7, 2012. In addition to microbial deterioration of stone, paper and wood, available technologies and innovations in removal and protection of cultural property, monitoring fungal contamination and classification of the contamination level, this symposium showed results dealing with cultural property after earthquake and tsunami as the key issues affecting the artifacts and cultural property highlighted at this symposium. Interestingly, it was found that salt in water can control the growth of molds and fungi on documents and less growth was observed when salinity was higher. This has a greater implication when dealing with large amounts of documents after natural disaster. The papers derived from invited speakers and also posters are being published in a dedicated volume of book available to research scientists, conservationists, applied biologists and graduate students working on related subjects.     

Biodegradation of ivory (natural apatite): possible involvement of fungal activity in biodeterioration of the Lewis Chessmen

Fungal biodeterioration of ivory was investigated with in vitro inoculation of samples obtained from boar and walrus tusks with the fungi Aspergillus niger and Serpula himantioides, species of known geoactive abilities. A combination of light and scanning electron microscopy together with associated analytical techniques was used to characterize fungal interactions with the ivory, including changes in ivory composition, dissolution and tunnelling, and the formation of new biominerals. The research was aimed at providing further understanding of the potential roles of fungi in the colonization and deterioration of ivory in terrestrial environments, but also contributes to our knowledge regarding the possible origins of the surface damage observed on early medieval sculptures made largely from walrus tusks, referred to as ‘the Lewis hoard of gaming pieces’, that were presumably produced for playing chess. The experiments have shown that the possibility of damage to ivory being caused by fungi is realistic. Scanning electron microscopy revealed penetration of fungal hyphae within cracks in the walrus tusk that showed also widespread tunnelling by fungal hyphae as well as ‘fungal footprints’ where the surface was etched as a consequence of mycelial colonization. Similar phenomena were observed with boar tusk ivory, while production of metabolites could lead to complete dissolution of the sample. Colonization of ivory and/or exposure to fungal activity lead to extensive secondary biomineral formation, and this was identified as calcium oxalate, mainly as the monohydrate, whewellite.     

Analysis of the potential fungal biodeteriogen effects in the “Doctorate Library” of the University of Perugia,Italy

Historical collections held in ancient archives and libraries constitute a cultural and artistic heritage of inestimable value. These collections contain a series of organic materials which may alter and perish in time, especially if they are conserved in inadequate environmental conditions and without any specific precautionary devices to protect them from damage caused by chemical, biological and physical factors. It is essential to prevent ‘at risk’ situations to conserve library and archive heritage. Early detection of fungal spores and moulds in conservation environments will permit us to intervene at the infection site at the right moment and also to detect the micro‐environments where climatic parameters are not suitable for conservation purposes.

The aim of this study is to examine potentially biodeteriogen fungal micro‐flora in the environment of the “Doctorate Library”, one of the most important buildings of the University of Perugia, which contains frescos and library collection of great value. The study was carried out through quantitative and qualitative analysis of airborne fungal species and through the evaluation of viable aerobiological particles as potential agents of biodeterioration. The airspore monitoring was made using the active method (by Personal Volumetric Air Sampler Spore Trap, Burkard Company Ltd.) and the passive one (by sedimentation technique on Petri dishes). The results obtained by both methods allowed us to detect numerous potentially biodeteriogen species, to determine their quantity and influence and to evaluate the levels of their variability in time.     

Microbial deterioration of gelatin emulsion photographs: Differences of susceptibility between black and white and colour materials

Microbial deterioration is a common problem in photographic collections, and has been considered a major cause of deterioration. However, few studies have been carried out on this topic, and most of the literature concerns biodeterioration of archival documents in general, including both micro- and macroorganisms. There have been no detailed studies on the interactions between microorganisms, environment, and the composition of photographic material. This study focuses on fungal deterioration of gelatin emulsion photographs. It was part of a study of three collections in Lisbon, Portugal. The first part is quantitative research on the fungal contamination of the Horácio Novais collection, and the second involves induced contamination of experiments on gelatin emulsion photographs. At the end these data are analysed, taking into account the hypothesis that colour materials are more susceptible to fungal deterioration than are black and white ones. This hypothesis is based on the observations of professionals working with photograph collections who report that, at least in plastic base supports (negatives and slides), colour materials are frequently more contaminated than the black and white ones. An overall look at the results seems to indicate a higher susceptibility of the colour chromogenic photographic materials to fungal colonization compared to the black and white materials. However, this hypothesis could not be absolutely confirmed by this study.     

文化遗产微生物研究方法进展

文化遗产的生物退化与生物降解问题普遍存在。从方法学的角度回顾了针对不同类型文化遗产微生物病害与防治研究中常用的方法和技术,总结了国内外当前所取得的主要研究进展,提出了该领域研究中未来面临的问题和挑战,并展望了应对策略和今后发展趋势。文化遗产微生物研究方法经历了传统培养、显微镜分析、分子生物学技术、酶活性和代谢产物分析以及快速发展的多组学及生物信息学分析等多个阶段,在微生物多样性、群落特征、生理生态学及其退化机理方面的认识已逐渐深入,以文化遗产保护为目标的病害微生物防治技术不断发展。近年来通过新一代测序和宏基因组学技术获得了文化遗产微生物的诸多重要信息,但其作用机理和影响因素的研究还不够。本综述突出了结合传统与现代方法技术开展研究的重要性,旨在为文化遗产微生物学领域研究提供参考和借鉴。     

Biodeterioration of ancient stone materials from the Persepolis monuments (Iran)

The problem of deterioration of art works is particularly relevant in countries like Iran that are rich in cultural heritage. According to UNESCO data, Iran holds the tenth rank in a list of countries possessing the highest number of monuments belonging to the world cultural heritage. Archaeological areas, buildings, mosques, statues, museums and objects are all exposed to different biogenic and abiogenic stresses under generally aggressive climatic conditions. Lichens and fungi are known to actively decompose stone surfaces. This process is both physical and chemical in nature and often reaches deep below the stone surfaces. This is caused by chemical and physical interactions of the microbiota with the fluctuating and often drastically changing environmental conditions. Here, we describe and analyze the mainly physical degradation by invading fungal hyphae between stone crystals and a generally destabilizing stone texture. In addition to physical deterioration, organic acids produced by lichens enhance the chemical decomposing processes. In this work, penetration of hyphal bundles as well as individual fungi was studied, and the biodeteriorating patterns were documented and compared to general physical–chemical weathering phenomena. Several strains of aggressive black yeast-like fungi and bacteria were isolated and cultivated and will be described in a taxonomical context with many other isolates from different localities using physiological, morphological and molecular data.     

The revenge of time: fungal deterioration of cultural heritage with particular reference to books, paper and parchment

Hyphomycetous fungi - so called 'mould'- are the most important agents of biodeterioration in museums, museums' storage rooms, in libraries, collections and restoration studios. Fungi are able to live at low water activities, they are perfectly adapted to indoor environments and thrive in microclimatic niches caused by condensation, lack of ventilation or water retention by hygroscopic materials. Fungi spoil valuable pieces of art aesthetically, mechanically, chemically and by degradation of organic components. Historical material made of paper and oil paintings with high amounts of organic binders are especially susceptible to fungal deterioration. In order to prevent fungal contamination or to treat already contaminated objects an integrated approach including climate control, material-specific cleaning and application of carefully selected biocides is necessary.     

Contamination of mural paintings by indoor airborne fungal spores

Summary The processes of biodeterioration on mural paintings have often been discussed, whereas the causes of contamination have seldom been examined.Many microorganisms responsible for the biodeterioration of paintings are of airborne origin. It follows that an investigation on the aerial microbial concentration and air movements in painted indoors is very useful.This paper reviews the literature of mural painting biodeterioration and the aerobiological studies of painted indoors. Hypogean environments, for their particular microclimatic conditions, are not considered.The fungal species most frequently found in the biodeterioration of wall-paintings are reported, as well as comparisons of surface contamination and aerobiological investigation.This review shows the necessity of finding the best sampling methodologies for cultural heritage studies. The control of airborne contamination and proper sampling methods are highly important in determining treatment strategies for the conservation and prevention of microbial attack on painted surfaces.     

Skeleton bones in museum indoor environments offer niches for fungi and are affected by weathering and deposition of secondary minerals

Large skeleton specimens are often featured as iconic open displays in Natural History Museums, for example, the blue whale ‘Hope’ at the Natural History Museum, London. A study on Hope's bone surface was performed to assess the biodeterioration potential of fungi. Fungi were isolated, and a fungal internal transcribed spacer (ITS) clone library survey was performed on dust and bone material. Mineral particles derived from bone and dust were analysed using energy dispersive X-ray spectroscopy, variable pressure scanning electron microscopy (SEM) and high vacuum SEM. Results showed that bone material, although mainly mineral in nature, and therefore less susceptible than organic materials to biodeterioration phenomena in the indoor environments, offers niches for specialized fungi and is affected by unusual and yet not so well-documented mechanisms of alteration. Areas of bone surface were covered with a dense biofilm mostly composed of fungal hyphae, which produced tunnelling and extensive deposition of calcium and iron-containing secondary minerals. Airborne halophilic and xerophilic fungi including taxa grouping into Ascomycota and Basidiomycota, capable of displacing salts and overcome little water availability, were found to dominate the microbiome of the bone surface.     

Biodeterioration and cellulolytic activity by fungi isolated from a nineteenth-century painting at the National Theatre of Costa Rica

Living organisms can induce deterioration of cultural heritage. Conservation strategies aimed at avoiding damage and aiding restoration, require a comprehensive knowledge of structure, chemical composition, and identity of microorganisms that colonize artworks. The National Theatre of Costa Rica (NTCR), a building with historic architecture, houses several oil paintings from the nineteenth century, some with visible signs of biodeterioration. One of them is a large format painting on canvas called La Danza (size 9.83 × 5.13 m) from 1896 by Italian artist Vespasiano Bignami, located on the ceiling of the theatre's foyer. In the present study, we undertook a physicochemical and microbiological study of La Danza to identify the fungal species that inhabit the artwork and are responsible for the damage observed. Scanning electron microscope (SEM) images and attenuated total reflectance - Fourier transform infrared (ATR-FTIR) spectroscopic data indicated that the canvas material is made of hemp, the binder contains linseed oil and lead white, and a material in the inner face of the canvas is mainly composed of beeswax. Fungi were isolated onto potato dextrose agar (PDA) and carboxymethyl cellulose (CMC) agar, and then identified with molecular (BTUB, nrDNA ITS, and TEF1 regions) and morphological methods. Four isolates belonging to the genera Myxospora, Pestalotiopsis, Ustilago, and aff. Penicillium, were obtained. Qualitative tests showed cellulolytic activity in all isolated specimens, confirming their possible role in biodeterioration of the canvas. Phylogenetic and morphological data revealed a new species of Myxospora we name here as Myxospora theatro sp. nov., in reference to NTCR. The findings broaden the knowledge of fungi capable of inhabiting and damaging cultural heritage. They also provide valuable information to develop strategies for conservation and restoration of oil paintings on canvas.     

Application of electronic nose technology for the detection of fungal contamination in library paper

Studies were carried out in vitro on a cellulose based agar at two water activities (a_w,0.975,0.995) and on three types of paper at two relative humidities (75, 100% RH) for the potential for differentiation of contamination and colonisation by Aspergillus terreus, A. holandicus and Eurotium chevalieri. In vitro studies showed that conducting polymer sensor array gave different responses to each of these species when grown on cellulose agar at both a_w levels. Discriminant function analyses of the data showed differentiation of the controls from the spoilage fungi. Cluster analysis gave a significant (P=0.05) separation of the control and each spoilage fungus. In situ studies on three types of paper showed that using natural substrates the volatile patterns produced by each of these fungi was different from each other and from the control. The results obtained were better at the higher humidity. The three paper types could be successfully differentiated into clusters. For a single paper type, differentiation of controls from spoilage fungal treatments was better at the higher humidity. This study has shown that this technology has potential for the early detection of fungal contamination in library materials and archives for the improved protection of cultural heritage.     

石质文物地衣生物腐蚀及防治的研究进展

本文主要从生物因素方面考虑,分析了导致石质文物病害的主要原因和机理,并综述了国内外石质文物保护的现状、防治和修复方法。地衣是引起石质文物腐蚀的关键生物类群,与国外相比,目前国内专门针对地衣进行石质文物防治的研究鲜见报道。作者建议,石质文物的地衣生物腐蚀及防治研究应从以下方面入手：（1）石质文物地衣必须首先进行系统的种类调查;（2）对地衣腐蚀石质文物的机理进行深入研究;（3）探寻地衣病害安全有效的去除方法;（4）逐步探索地衣病害修复后的监测和预防方法。