INTRODUCTION. There is now a high level of acceptance amongst biodeterioration biologists and technologists in the paints and biocides industries , that. Several paints of varying chemistry have been in use for domestic and industrial purposes. The painted Biodeterioration of domestic and public buildings. PDF | This paper presents a review of the biodeterioration of architectural paint films by bacteria, fungi and algae, concentrating on external films. references .
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In four young men discovered the Lascaux Cave in the Dordogne region of France. The cave contained an impressive display of prehistoric art: The approximately paintings, done with mineral pigments bioedterioration with animal fat in various shades of yellow, red, brown, and black, were dated to the late Aurignacian period 15, to 13, B.
With few exceptions, the paintings, some as long as 5 m, represented different animals some imaginaryand their quality was such that the cave was designated by some the Sistine Chapel of the Paleolithic.
In Lascaux Cave was opened to visitors, but in it was closed indefinitely to the public. Closing was imposed after the discovery of a green patina from which comes the term maladie verteor green disease covering the painted portions Quite unexpectedly, although other algae together with cyanobacteria, bacteria, and fungi were isolated in different parts biodeterioratoon the cave, the green patina was composed exclusively of the unicellular alga Bracteacoccus minor order Chlorococcales.
The lighting system, installed in the cave and operating almost continuously, created the conditions for a massive growth of photosynthetic organisms. Extensive analysis of the composition of, and the variations in, the microbial population of the painted areas as well as of the unpainted rocks and the surrounding environment led to the conclusion that the population of Bracteacoccus minorresponsible for the maladie bioedteriorationalso increased when the cave was closed to the public and kept in continuous darkness for long periods.
Paihts, after 3 months of total darkness and bioedterioration to the public, algal proliferation on painted areas was found to have increased by 1 order of magnitude Thus, it was concluded that the alga could grow even under heterotrophic conditions by utilizing the organic molecules brought in the cave by visitors or resulting from the degradation of biological residues.
It was postulated that, before discovery and opening of the cave, the community of heterotrophic microorganisms, bacteria and fungi, present in the cave had mineralized all organic molecules present, so that heterotrophic growth of the alga was prevented, as was autotrophic growth as a result of the absence of light.
The Lascaux Cave is perhaps the most emblematic example of the damage that microorganisms may cause to art work and should settle once and forever the arguments about the possible role of microorganisms in the degradation of our cultural heritage. The conditions that led to the microbial bloom on the Lascaux Cave paintings probably represent an extreme case, but it may be argued convincingly that even less harsh environmental stresses than those that occurred in the less than 20 years since the opening of the Lascaux Cave may cause irreversible aesthetic and structural damage to almost any type of art work.
This minireview focuses on the colonization of art works by microorganisms and its effects. Its scope will be limited to paintings, both on canvas and panel, as well as on walls.
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Thus, other art works, such as those in stone, wood, paper, and masonry, as well as those in more esoteric materials, such as leather, parchment, glass, and metal, will not be considered. For a more comprehensive treatment of the role of microorganisms in the degradation of our cultural heritage, the reader should refer to the reviews already published 261213202930364655 Paintings, whether easel or mural, contain a wide range of organic and inorganic constituents and provide different ecological niches that may be exploited by a large variety of microbial species.
Many of the components of paintings are biodegradable, and so are the additives biodeteriofation, emulsifiers, thickeners, etc. Paintings on paper or silk are laid, in general, directly on the support, since a ground or underlay is lacking, but the pigments are kept in emulsion with organic binders. Thus, besides the organic nature of the support, easel paintings contain organic molecules that many microorganisms may utilize for growth, such as sugars, gums, and other polysaccharides, proteins, linseed and other oils, waxes, etc.
A list, certainly not exhaustive, of the organic components that may be present on paintings can be found in references 15 and Mural paintings rely on techniques and materials differing from those utilized in easel paintings. Essentially, pigments are suspended in water or oil, often in the presence of binders such as casein and milk, and applied on the damp lime plaster.
The calcium carbonate formed on contact with air consolidates the pigments. Thus, by and large, frescoes contain mainly inorganic components and the microbial flora that colonize these substrates may, at least in the first biodeterioation, differ from that present on easel paintings.
For both types of paintings the spectrum of compounds that may be present is further increased by those that are added at later times during retouching, restoration, or relining or when a fresco is detached and transferred to a canvas or a board. In one case at least, extensive fungal colonization was reported even with frescoes that, after cleaning and consolidation, were removed from walls and transferred to a fiberglass support Finally, dirt, soot, and other environmental contaminants, accumulating on the painted surface, may represent another not insignificant source of nutrients.
Given the wide range of organic and inorganic molecules that are present in both types of paintings, many different types of microorganisms may grow on such substrates provided that favorable environmental conditions humidity, temperature, light, and, to a lesser extent, pH are met.
It sounds almost tautological biodeterikration state that, besides the chemical composition of an art work, the environment conditions the development of a microbial flora, as it is quite obvious that a specific microbial flora will develop, for instance, on a fresco on the facade of a bidoeterioration where it receives a considerable amount of light and biodeterioratiom different flora will develop on a similar fresco inside the same building in which light is very reduced.
Likewise, if temperature, moisture, and light are not controlled, the microbial communities of two paintings produced with exactly the same materials will differ considerably if one painting is kept in the northern latitudes and the other is kept in the tropics. It may be added that high levels of humidity, temperature, and light, as may be found, for instance, in warmer climates, may shorten the, one could pxints, life span of a painting by exacerbating the damages caused by air pollution, biological attack, and natural aging.
Growth of microorganisms on paintings may cause aesthetic and structural damage. As aesthetic damage one must consider pigment discoloration, stains, and formation of a biofilm on the painted surface, whereas as structural damage one must consider bipdeterioration and disintegration of paint layers, formation of paint blisters, and degradation of support polymers or of glues and binders resulting in detachment of the paint layer from the support.
Of course, the two types of damage are strongly linked, and in the long run, structural damage profoundly affects the aesthetic quality of a painting.
Conversely, aesthetic damage may precede serious injuries to the materials. Later on, fungal growth in depth occurred. Hyphae penetrated the painted layer, degrading some of its components especially glues and binderswhich resulted in a decrease in the cohesion of the painted layers, thus giving rise to exfoliations, cracking, and loss of the paint. To these damages one should add those inflicted by metabolites, often acidic in nature, and by extracellular enzymes excreted by microorganisms.
Microbial Degradation of Paintings
bioedterioration These compounds may modify the colors as well as the stability of the painted layer and of the substrate. Similarly, cyanobacteria and algae growing on paintings exposed biodeteriooration light, such as frescoes on the facades of buildings, may cause considerable damage. Besides the aesthetic damage caused by a green, black, brown, or yellow algal patina covering the painted portions, these organisms may cause weathering of the surface layers, accelerating detachment of portions of the painted paimts as well as the underlying plaster The presence in a number of Italian biodeterikration of species of nitrogen-fixing Nostoc indicates that cyanobacteria may colonize frescoes in which combined nitrogen may be absent Indeed, in this investigation, determination of acetylene reduction in situ demonstrated that nitrogen fixation occurred, albeit at a reduced rate, in the microbial biofilm covering the frescoes.
In addition, cyanobacteria and algae can provide an important source of organic material on which heterotrophic bacteria and fungi may thrive, thus causing further aesthetic and structural damage to the paintings. Finally, cyanobacteria and algae biodetrrioration colonize the mortar, bricks, or stone supporting frescoes. Indeed, these organisms have been reported to contribute to the weathering process of masonry With a few exceptions, characterization of the microbial flora present on frescoes or easel paintings has been limited to selected groups of microorganisms rather than to all types of microorganisms that might be present on a given substrate.
Thus, in general, surveys have often been limited to fungi 1810141722 — bodeterioration37475057bacteria 718323344biodeteriroationor cyanobacteria and eukaryotic algae 9162140 In a few cases, more comprehensive analyses aiming to determine all, or the majority of, the biota present on a painting have been reported 27 This comprehensive data may provide the foundation for ascertaining the existence of associations or successions among the components of a microbial flora.
Recently, a method of identifying microorganisms by sequencing a portion of the DNA coding for the 16S rRNA has been used with cultures of bacteria biodeterioratoon from frescoes 744 and even with DNA samples extracted directly from a fresco 44 This technique, extensively employed in macromolecular ecology to identify, without culturing, members of microbial communities, will boodeterioration lengthen the list of microorganisms present on any given substrate by permitting, for instance, the identification of species that are present at very low cell concentrations and of those that cannot be cultured painys the laboratory.
However, it will not determine if the DNA derives from living or dead microorganisms and, more importantly, it will not allow us to distinguish between microorganisms responsible for the observed damage one could call them the parasites and those that do not contribute to it the saprophytes.
Similar limitations will greatly reduce the usefulness of other molecular biological techniques, such as fluorescence in situ hybridization, that permit identification of microorganisms without their isolation and culture.
Perusal of the lists of taxa isolated shows that the most common soil inhabitants, both fungi species of PenicilliumAspergillusCladosporiumChaetomiumand Alternaria and bacteria species of PseudomonasArthrobacterand Streptomycesare present in many of the samples analyzed. However, wide quantitative variations are evident. For instance, from a fresco in St.
On the other hand, from a mural in Canterbury Cathedral only one fungal species, Beauveria alba Engyodontium albumwas repeatedly isolated 26 and, similarly, on damaged frescoes in an Italian church only one species of Cladosporium was found Further, in laboratory experiments, they demonstrated that treatment with fungicides could arrest or prevent microbe-induced damage to paintings.
About 20 years later, Tonolo and Giacobini 59 confirmed that microorganisms could damage works of art by providing examples of frescoes disfigured by growth of eukaryotic algae members of Chlorophyceaebacteria Sarcina lutea or Streptomyces spp. In addition, they showed that many such organisms, especially the fungi, could grow between the paint layers and the ground, causing a swelling of the paint film that could lead to detachment of portions of the painted layer and disaggregation of the underlying ground.
This in turn could promote separation of the painted surface from the ground or of the ground from the masonry on which the fresco was laid. After these pioneering papers, Gargani 14 and Tiano and Gargani 57 published a detailed investigation of the microbial floras of art works, mostly frescoes. Their work was greatly stimulated by the finding that, after the flooding of Florence in Novembera great number of paintings, painnts mural and easel, were severely damaged and that the damage could be at pwints in part associated with the growth of microorganisms.
Using a technique of dermatologic mycology, they determined that direct microscopic examination of the microbial structures adhering to transparent cellulose tape pressed on the painted surface revealed the presence of fungal elements, such as hyphae, typical of most filamentous fungi.
However, species identification and determination of the microbial load were possible only when cultures on different media were made with small fragments of the painted surface or cotton swabs brushed on such a surface. The analyses were essentially limited to the fungal population and demonstrated that clear differences existed between the numbers of species isolated from art works and those isolated from the environment in which the art work was located.
For instance, from the surface of a fresco by Beato Angelico in St. These data could be taken as an indication of the presence of a fungal flora specifically developing on the painting and differing, at least in part, from that present in the environment.
However, sampling at different intervals months revealed significant differences in the compositions of the flora of the painted surface whereas there was little variation from sampling to sampling in the flora of the environment. Similar wide variations in the species isolated from different periods were reported in the analyses of the microbial, essentially fungal, flora present on wall paintings in the Buddhist shrines of Ajanta in India 1.
Two 15th-century murals in the Ognissanti church in Florence, restored in after the flood ofwere cleaned and treated with nystatin in the late s but, inshowed the appearance of greenish-brown—to—black spots on the painted surface However, striking differences in the types of species were evident: Such differences in two frescoes painted at the same time in the same building, presumably with similar or identical materials, and restored and cleaned at the same time appear rather striking.
In laboratory experiments, 19 species of the fungi isolated from the two frescoes were tested for the capacity to grow on the materials used for restoration calcium caseinate, animal glue, and masonite, used as a support panel. Although qualitative differences were observed, essentially all the fungal species isolated from both frescoes grew quite well on calcium caseinate, to a lesser extent on masonite, and to an even lesser extent on animal glue.
The only exception was provided by the two species of Cladosporiumwhich, although being among the most frequent isolates from the two frescoes, did not grow well on any of these materials. In the opinion of the investigators, this genus is one of the most commonly isolated from frescoes because it is resistant to variations in external factors temperature, humidity, etc.
However, as the two tested species of Cladosporium did not grow on casein, masonite, or animal glue, the investigators assumed that this genus did not contribute significantly to the degradation of paintings. This assumption is in contrast to the opinion of other scientists who consider Cladosporium one of the major biological agents, if not the most significant agent, responsible for fresco degradation 21937 In conclusion, the differences observed in the fungal colonizations of the two frescoes are not easily explained.
Assuming that no great differences exist in the materials used when the two frescoes were painted but this cannot be provedthe only possible explanation is that the locations of the two frescoes in the church are such that they affect differentially the fungal colonizations of the two murals. One can argue that the positions of the frescoes relative to openings windows or doorssources of moisture and heat, and other factors may be responsible for the differences in the fungal colonizations.
In an extensive investigation of the fungal colonizations of frescoes in eight different Moldavian monasteries, Ionita 25 isolated 26 different species of fungi from stains appearing on the frescoes, from areas of efflorescence, and from zones in which the painted layer was fissured and portions were breaking away from the support.
No apparent recognizable pattern in the fungal distribution could be observed. For instance, from three areas with stains of the same color, present on the same portion of a fresco, different fungi were isolated.
In addition, the same fungal species was isolated from spots of different colors as well as from fissured fragments of the frescoes that were apparently not stained. Further, Aspergillus nigerone of the most ubiquitous fungal contaminants, was isolated in only one case. Such variations in the fungal floras present in samples taken at different times, or in frescoes of the same age and in the same location, were often observed and do not allow us to establish conclusively that the fungi present on a painted surface, even when they are absent from the environment, are responsible for the damage observed on the paintings.
Further, no attempt has been made to identify the species responsible for the damage, both aesthetic and structural, and the species that are just saprophytes living on the painted surface may be growing at the expense of other microorganisms colonizing the frescoes. However, the idea that fungi may be the primary microbiological agents responsible for degradation of art works is so entrenched that often antibacterial agents are added routinely to the media used for the isolation of the microbial contaminants presumed responsible for the degradation of art works 22 With frescoes located underground, such as those in crypts, tombs, and grottoes, it has been reported that the predominant species and, possibly, the first colonizers are members of the order Actinomycetalesmost of which are in the genus Streptomyces and a few of which are in the genus Nocardia Over strains of actinomycetes were isolated from 13 frescoes in different Italian hypogean sites.
Of the isolates, 46 were identified as members of 19 different species of Streptomyces and 5 were identified as members of the genus Nocardia. According to the researchers, colonization by actinomycetes begins as soon as the sites are opened and the frescoes are excavated, becoming quite evident only 2 months after excavation and exposure to air. In a short period, other microorganisms bacteria, fungi, and algae become associated with the predominant population of actinomycetes.