Diversity of fungi associated with petroglyph sites in the Negev Desert, Israel, and their potential role in bioweathering.

The petroglyphs of the Negev Desert, Israel, are famous and valuable archaeological remains. Previous studies have investigated the microbial communities associated with petroglyphs and their potential role in stone deterioration; nevertheless, the role of fungi remains unclear. In this study, the fungal communities present on the stone and, as a comparison, in the surrounding environment (soil and air) at Negev petroglyph sites were analyzed by means of culture-dependent and -independent (metagenomic) techniques. The metagenomic results showed a high fungal biodiversity in the soil, and both approaches highlighted the prevalence of species producing melanized, large, thick-walled spores (mainly Alternaria spp.). From the air sampling, mostly Cladosporium spp. were retrieved. On the other hand, on the rock, the results seem to indicate a low presence of fungi, but with a rock-specialized mycobiota consisting of extremotolerant microcolonial fungi (MCF) (e.g., Vermiconidia and Coniosporium) and lichens (Flavoplaca). In addition, low proportions of cosmopolitan fungi were detected on the stone, but the comparison of the data clearly indicates that they are transients from the surrounding environment. The ability of the isolated strains to dissolve CaCO3 and therefore be a potential threat to the petroglyphs (limestone substrate) was tested, but only one strain resulted in positive acid production under laboratory conditions. Nevertheless, both lichens and MCF detected in this study are well-known stone deteriogens, which may have a significant impact on the petroglyph's deterioration.

Fungal Biodeterioration Risk in Monastic Libraries without Climate Control.

Fungi have always posed an unquestionable threat to heritage collections worldwide. Now, in a future of climate change, biological risk factors may have to be considered even more than before. Models and simulations to assess possible impacts a changing outdoor climate will have on indoor environments and, in turn, on biodeterioration are still underdeveloped and require a more substantial data basis. This study aimed at filling some of these knowledge gaps through a broad-based approach combining microclimatic and microbiological monitoring in four historic libraries in Austria with an uncontrolled indoor climate: Altenburg Abbey, Melk Abbey, Klosterneuburg Monastery and the Capuchin Monastery in Vienna. Data were generated from thermohygrometric sensors, cultivation-dependent air- and surface sampling and further surface dust sampling for cultivation-independent analyses. Results gave insights on the status quo of microbiological loads in the libraries and outdoor-indoor relationships. Influences of the geographic location and room-use on corresponding indoor fungal profiles were identified. Lower fungal diversities were found at the most rural site with the strongest climatic fluctuations and extreme values than in the most urban, sheltered library with a very stable climate. Further, the humidity-stabilizing potential of large collections of hygroscopic materials, such as books, was also examined. Implications for a sustainable approach to prevent future biodeterioration are discussed, supporting the long-term preservation of these valuable historic collections.

Pretty in pink? Complementary strategies for analysing pink biofilms on historical buildings.

Salt-weathering is a deterioration mechanism affecting building materials that results from repetitive cycles of salt crystallisation-dissolution in the porous mineral network under changing environmental conditions, causing damage to surfaces. However, an additional biodeterioration phenomenon frequently associated with salt efflorescence is the appearance of coloured biofilms, comprising halotolerant/halophilic microorganisms, containing carotenoid pigments that cause pinkish patinas. In this work, two Austrian historical salt-weathered buildings showing pink biofilms, the St. Virgil's Chapel and the Charterhouse Mauerbach, were investigated. Substrate chemistry (salt concentration/composition) was analysed by ion chromatography and X-ray diffraction to correlate these parameters with the associated microorganisms. Microbiomes were analysed by sequencing full-length 16S rRNA amplicons using Nanopore technology. Data demonstrates that microbiomes are not only influenced by salt concentration, but also by its chemical composition. The chapel showed a high overall halite (NaCl) concentration, but the factor influencing the microbiome was the presence/absence of K+. The K+ areas showed a dominance of Aliifodinibius and Salinisphaera species, capable of tolerating high salt concentrations through the "salt-in" strategy by transporting K+ into cells. Conversely, areas without K+ showed a community shift towards Halomonas species, which favour the synthesis of compatible solutes for salt tolerance. In the charterhouse, the main salts were sulphates. In areas with low concentrations, Rubrobacter species dominated, while in areas with high concentrations, Haloechinothrix species did. Among archaea, Haloccoccus species were dominant in all samples, except at high sulphate concentrations, where Halalkalicoccus prevailed. Finally, the biological pigments visible in both buildings were analysed by Raman spectroscopy, showing the same spectra in all areas investigated, regardless of the building and the microbiomes, demonstrating the presence of carotenoids in the pink biofilms. Comprehensive information on the factors affecting the microbiome associated with salt-weathered buildings should provide the basis for selecting the most appropriate desalination treatment to remove both salt efflorescence and associated biofilms.

Natural sciences at the service of art and cultural heritage: an interdisciplinary area in development and important challenges.

Our cultural heritage is a common asset that tells the story of our shared past, is part of our origin and identity and has wide social relevance. Our works of art and our heritage must be enjoyed, appreciated and preserved for future generations. To this end, a wide and varied group of professionals, including conservators, restorers, curators, bibliographers, historians, archivists, but also scientists, such as biologists, chemists, physicists and bioinformaticians, work side by side to preserve our cultural heritage. Working together in this wide range of disciplines included in the so-called 'heritage sciences' is the only plausible way to contribute to the sustainable preservation of our heritage. The great progress made in recent years in conservation and restoration work, but also in the natural sciences considered within heritage science, has provided powerful tools and strategies for analytical and experimental research into historical and cultural objects that open up new frontiers for their diagnosis, monitoring and protection. Here we highlight some of the advances and challenges faced by the natural sciences at the service of art.

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.

Contamination of wounds with fecal bacteria in immuno-suppressed mice.

Immunocompromised patients are predisposed to chronically infected wounds. Especially ulcers in the dorsal region often experience secondary polymicrobial infections. However, current wound infection models mostly use single-strain bacteria. To mimic clinically occurring infections caused by fecal contamination in immunocompromised/immobile patients, which differ significantly from single-strain infections, the present study aimed at the establishment of a new mouse model using infection by fecal bacteria. Dorsal circular excision wounds in immunosuppressed mice were infected with fecal slurry solution in several dilutions up to 1:8,000. Impact of immunosuppressor, bacterial load and timing on development of wound infections was investigated. Wounds were analyzed by scoring, 3D imaging and swab analyses. Autofluorescence imaging was not successful. Dose-finding of cyclophosphamide-induced immunosuppression was necessary for establishment of bacterial wound infections. Infection with fecal slurry diluted 1:166 to 1:400 induced significantly delayed wound healing (p < 0.05) without systemic reactions. Swab analyses post-infection matched the initial polymicrobial suspension. The customized wound score confirmed significant differences between the groups (p < 0.05). Here we report the establishment of a simple, new mouse model for clinically occurring wound infections by fecal bacteria and the evaluation of appropriate wound analysis methods. In the future, this model will provide a suitable tool for the investigation of complex microbiological interactions and evaluation of new therapeutic approaches.

Decoding the biological information contained in two ancient Slavonic parchment codices: an added historical value.

This study provides an example in the emerging field of biocodicology showing how metagenomics can help answer relevant questions that may contribute to a better understanding of the history of ancient manuscripts. To this end, two Slavonic codices dating from the 11th century were investigated through shotgun metagenomics. Endogenous DNA enabled to infer the animal origin of the skins used in the manufacture of the two codices, while nucleic sequences recovered from viruses were investigated for the first time in this material, opening up new possibilities in the field of biocodicology. In addition, the microbiomes colonizing the surface of the parchments served to determine their conservation status and their latent risk of deterioration. The saline environment provided by the parchments selected halophilic and halotolerant microorganisms, which are known to be responsible for the biodegradation of parchment. Species of Nocardiopsis, Gracilibacillus and Saccharopolyspora, but also members of the Aspergillaceae family were detected in this study, all possessing enzymatic capabilities for the biodeterioration of this material. Finally, a relative abundance of microorganisms originating from the human skin microbiome were identified, most probably related to the intensive manipulation of the manuscripts throughout the centuries, which should be taken with caution as they can be potential pathogens.

Back to the Salt Mines: Genome and Transcriptome Comparisons of the Halophilic Fungus Aspergillus salisburgensis and Its Halotolerant Relative Aspergillus sclerotialis.

Salt mines are among the most extreme environments as they combine darkness, low nutrient availability, and hypersaline conditions. Based on comparative genomics and transcriptomics, we describe in this work the adaptive strategies of the true halophilic fungus Aspergillus salisburgensis, found in a salt mine in Austria, and compare this strain to the ex-type halotolerant fungal strain Aspergillus sclerotialis. On a genomic level, A. salisburgensis exhibits a reduced genome size compared to A. sclerotialis, as well as a contraction of genes involved in transport processes. The proteome of A. sclerotialis exhibits an increased proportion of alanine, glycine, and proline compared to the proteome of non-halophilic species. Transcriptome analyses of both strains growing at 5% and 20% NaCl show that A. salisburgensis regulates three-times fewer genes than A. sclerotialis in order to adapt to the higher salt concentration. In A. sclerotialis, the increased osmotic stress impacted processes related to translation, transcription, transport, and energy. In contrast, membrane-related and lignolytic proteins were significantly affected in A. salisburgensis.

Big Sound and Extreme Fungi-Xerophilic, Halotolerant Aspergilli and Penicillia with Low Optimal Temperature as Invaders of Historic Pipe Organs.

Recent investigations have shown that xerophilic fungi may pose a biodeterioration risk by threatening objects of cultural heritage including many types of materials, including wood, paint layers, organic glues or leather and even metal. Historic—and also new built—pipe organs combine all those materials. In this study, halotolerant aspergilli and penicillia with low optimal temperatures were shown to be the most frequent invaders of pipe organs. The fungi form white mycelia on the organic components of the organs with a clear preference for the bolus paint of the wooden pipes, the leather-made hinges of the stop actions and all parts fixed by organic glue. Physiological tests showed that the strains isolated from the instruments all show a halotolerant behavior, although none was halophilic. The optimum growth temperature is below 20 °C, thus the fungi are perfectly adapted to the cool and relatively dry conditions in the churches and organs respectively. The de-novo genome sequences analyses of the strains are currently ongoing and will reveal the genomic basis for the halotolerant behavior of the fungi.

Influence of compost and biochar on microbial communities and the sorption/degradation of PAHs and NSO-substituted PAHs in contaminated soils.

Diffusely contaminated soils often remain untreated as classical remediation approaches would be disproportionately expensive. Adding compost can accelerate the biodegradation of organic contaminants and adding biochar can immobilize contaminants through sorption. The combined use of compost and biochar to reduce polycyclic aromatic hydrocarbon (PAH) and NSO-substituted PAH contamination has, however, not previously been systematically investigated. We have therefore investigated the processes involved (i) through sorption batch experiments, (ii) by monitoring changes in bacterial, fungal and archaeal communities using denaturing gradient gel electrophoresis, and (iii) through degradation experiments with fluorene, phenanthrene, pyrene, carbazole, dibenzothiophene, and dibenzofuran. Sorption coefficients for organic contaminants in soils increased tenfold following 10% compost addition and up to a hundredfold with further addition of 5% biochar. The rate of PAH and NSO-PAH degradation increased up to twofold following compost addition despite increased sorption, probably due to the introduction of additional microbial species into the autochthonous soil communities. In contrast, degradation of PAHs and NSO-PAHs in soil-compost-biochar mixtures slowed down up to tenfold due to the additional sorption, although some degradation still occurred. The combined use of biochar and compost may therefore provide a strategy for immobilizing PAHs and NSO-PAHs and facilitating degradation of remaining accessible contaminant fractions.

Draft Genome Sequences of the Black Rock Fungus Knufia petricola and Its Spontaneous Nonmelanized Mutant.

The fungal genus Knufia mostly comprises extremotolerant species from environmental sources, especially rock surfaces. The draft genome sequence of the rock fungus Knufia petricola presented here is the first whole-genome sequence of the only species among black fungi known to have a nonmelanized spontaneous mutant.

Aspergillus atacamensis and A. salisburgensis: two new halophilic species from hypersaline/arid habitats with a phialosimplex-like morphology.

Halophilic fungal strains isolated from historical wooden staircase in a salt mine in Austria, and from wall biofilm and soil of a cave in the Coastal Range of the hyperarid Atacama Desert in Chile were characterised and described newly as Aspergillus salisburgensis and Aspergillus atacamensis. Morphological characters including solitary phialides producing solitary conidia and conidia in chains and/or heads suggested affinity to Aspergillus subgenus Polypaecilum. Strains required salt for growth, grew optimally on media with 10-25% NaCl and at 15-28 °C. These values are similar to those observed for Aspergillus salinarus comb. nov. (Phialosimplex salinarum), while the ex-type strains of Aspergillus sclerotialis, Aspergillus chlamydosporus and Aspergillus caninus (all belonging to Aspergillus subgen. Polypaecilum) grew optimally at 0-5% NaCl and showed fastest growth at 28-37 °C. Phylogenetic analyses on the basis of rDNA sequences, RAPD-PCR fingerprint patterns, and cellobiohydrolase gene (cbh-I) polymorphism clustered the strains into three groups and supported their taxonomic recognition as A. salinarus, A. atacamensis and A. salisburgensis. On the basis of phylogenetic inferences, also Sagenomella keratitidis is newly combined as Aspergillus keratitidis and inferred as a species of Aspergillus subgenus Polypaecilum.

Biodeterioration Risk Threatens the 3100 Year Old Staircase of Hallstatt (Austria): Possible Involvement of Halophilic Microorganisms.

BACKGROUND: The prosperity of Hallstatt (Salzkammergut region, Austria) is based on the richness of salt in the surrounding mountains and salt mining, which is documented as far back as 1500 years B.C. Substantial archaeological evidence of Bronze and Iron Age salt mining has been discovered, with a wooden staircase (1108 B.C.) being one of the most impressive and well preserved finds. However, after its discovery, fungal mycelia have been observed on the surface of the staircase, most probably due to airborne contamination after its find. OBJECTIVE: As a basis for the further preservation of this valuable object, the active micro-flora was examined to investigate the presence of potentially biodegradative microorganisms. RESULTS: Most of the strains isolated from the staircase showed to be halotolerant and halophilic microorganisms, due to the saline environment of the mine. Results derived from culture-dependent assays revealed a high fungal diversity, including both halotolerant and halophilic fungi, the most dominant strains being members of the genus Phialosimplex (synonym: Aspergillus). Additionally, some typical cellulose degraders, namely Stachybotrys sp. and Cladosporium sp. were detected. Numerous bacterial strains were isolated and identified as members of 12 different genera, most of them being moderately halophilic species. The most dominant isolates affiliated with species of the genera Halovibrio and Marinococcus. Halophilic archaea were also isolated and identified as species of the genera Halococcus and Halorubrum. Molecular analyses complemented the cultivation assays, enabling the identification of some uncultivable archaea of the genera Halolamina, Haloplanus and Halobacterium. Results derived from fungi and bacteria supported those obtained by cultivation methods, exhibiting the same dominant members in the communities. CONCLUSION: The results clearly showed the presence of some cellulose degraders that may become active if the requirements for growth and the environmental conditions turn suitable; therefore, these microorganisms must be regarded as a threat to the wood.

Molecular Tools for Monitoring the Ecological Sustainability of a Stone Bio-Consolidation Treatment at the Royal Chapel, Granada.

BACKGROUND: Biomineralization processes have recently been applied in situ to protect and consolidate decayed ornamental stone of the Royal Chapel in Granada (Spain). While this promising method has demonstrated its efficacy regarding strengthening of the stone, little is known about its ecological sustainability. METHODOLOGY/PRINCIPAL FINDINGS: Here, we report molecular monitoring of the stone-autochthonous microbiota before and at 5, 12 and 30 months after the bio-consolidation treatment (medium/long-term monitoring), employing the well-known molecular strategy of DGGE analyses. Before the bio-consolidation treatment, the bacterial diversity showed the exclusive dominance of Actinobacteria (100%), which decreased in the community (44.2%) after 5 months, and Gamma-proteobacteria (30.24%) and Chloroflexi (25.56%) appeared. After 12 months, Gamma-proteobacteria vanished from the community and Cyanobacteria (22.1%) appeared and remained dominant after thirty months, when the microbiota consisted of Actinobacteria (42.2%) and Cyanobacteria (57.8%) only. Fungal diversity showed that the Ascomycota phylum was dominant before treatment (100%), while, after five months, Basidiomycota (6.38%) appeared on the stone, and vanished again after twelve months. Thirty months after the treatment, the fungal population started to stabilize and Ascomycota dominated on the stone (83.33%) once again. Members of green algae (Chlorophyta, Viridiplantae) appeared on the stone at 5, 12 and 30 months after the treatment and accounted for 4.25%, 84.77% and 16.77%, respectively. CONCLUSIONS: The results clearly show that, although a temporary shift in the bacterial and fungal diversity was observed during the first five months, most probably promoted by the application of the bio-consolidation treatment, the microbiota tends to regain its initial stability in a few months. Thus, the treatment does not seem to have any negative side effects on the stone-autochthonous microbiota over that time. The molecular strategy employed here is suggested as an efficient monitoring tool to assess the impact on the stone-autochthonous microbiota of the application of biomineralization processes as a restoration/conservation procedure.

Amid the possible causes of a very famous foxing: molecular and microscopic insight into Leonardo da Vinci's self-portrait.

Leonardo da Vinci's self-portrait is affected by foxing spots. The portrait has no fungal or bacterial infections in place, but is contaminated with airborne spores and fungal material that could play a role in its disfigurement. The knowledge of the nature of the stains is of great concern because future conservation treatments should be derived from scientific investigations. The lack of reliable scientific data, due to the non-culturability of the microorganisms inhabiting the portrait, prompted the investigation of the drawing using non-invasive and micro-invasive sampling, in combination with scanning electron microscope (SEM) imaging and molecular techniques. The fungus Eurotium halophilicum was found in foxing spots using SEM analyses. Oxalates of fungal origin were also documented. Both findings are consistent with the hypothesis that tonophilic fungi germinate on paper metabolizing organic acids, oligosaccharides and proteic compounds, which react chemically with the material at a low water activity, forming brown products and oxidative reactions resulting in foxing spots. Additionally, molecular techniques enabled a screening of the fungi inhabiting the portrait and showed differences when different sampling techniques were employed. Swabs samples showed a high abundance of lichenized Ascomycota, while the membrane filters showed a dominance of Acremonium sp. colonizing the drawing.

A combined approach to assess the microbial contamination of the archimedes palimpsest.

A combined approach, using molecular and microscopic techniques, was used to identify the microbiota associated with the Archimedes Palimpsest, an unusual parchment manuscript. SEM analyses revealed the microbial damage to the collagen fibers and the presence of characteristic cell chains typical of filamentous bacteria and fungal spores. Molecular analysis confirmed a homogeneous bacterial community colonizing the manuscript. The phyla Proteobacteria and Actinobacteria were associated with this ancient parchment; the sequences were most related to uncultured clones detected in the human skin microbiome and in ephitelium, and to cultivated species of the genera Acinetobacter and Nocardiopsis. Nevertheless, a great variation was observed among the different sampled areas indicating fungal diversity. Blumeria spp. dominated in the healthy areas of the parchment while degraded areas showed disparate fungal communities, with dominant members of the genera Mucor and Cladosporium. In addition, the quantification of the ß-actin gene by real-time PCR analyses (qPCR) revealed a higher fungal abundance on degraded areas than on the healthy ones.

Unmasking the measles-like parchment discoloration: molecular and microanalytical approach.

Many ancient parchments are defaced by red or purple maculae associated with localized destruction of collagen fibres. Although the main characteristics of this damage were present in most of the manuscripts analysed by many authors, no common microbial or fungal denominator has been found so far, and little or no correspondence between the microbial or fungal species isolated from materials could be addressed. In this study, culture-independent molecular methods and scanning electron microscopy (SEM) were used to identify fungal and bacterial communities on parchments affected by the purple stains. Protocols for c extraction and nucleic-acid-based strategies were selected for assays examining the community structure of fungi and bacteria on biodeteriorated parchment. Both SEM and molecular analysis detected the presence of bacterial and fungal cells in the damaged areas. Halophilic, halotolerant proteolytic bacterial species were selected by the saline environment provided by the parchment samples. As common microbial denominators, members of the Actinobacteria, mainly Saccharopolyspora spp. and species of Aspergillus, were detected in all investigated cases. It is proposed that a relationship exists between the phenomenon of purple spots on ancient parchments and that of the 'red heat' phenomenon, known to be present in some products manufactured with marine salt.

Halophilic microorganisms are responsible for the rosy discolouration of saline environments in three historical buildings with mural paintings.

A number of mural paintings and building materials from monuments located in central and south Europe are characterized by the presence of an intriguing rosy discolouration phenomenon. Although some similarities were observed among the bacterial and archaeal microbiota detected in these monuments, their origin and nature is still unknown. In order to get a complete overview of this biodeterioration process, we investigated the microbial communities in saline environments causing the rosy discolouration of mural paintings in three Austrian historical buildings using a combination of culture-dependent and -independent techniques as well as microscopic techniques. The bacterial communities were dominated by halophilic members of Actinobacteria, mainly of the genus Rubrobacter. Representatives of the Archaea were also detected with the predominating genera Halobacterium, Halococcus and Halalkalicoccus. Furthermore, halophilic bacterial strains, mainly of the phylum Firmicutes, could be retrieved from two monuments using special culture media. Inoculation of building materials (limestone and gypsum plaster) with selected isolates reproduced the unaesthetic rosy effect and biodeterioration in the laboratory.

Quantification of fungal abundance on cultural heritage using real time PCR targeting the ß-actin gene.

The traditional methodology used for the identification of microbes colonizing our cultural heritage was the application of cultivation methods and/or microscopy. This approach has many advantages, as living microorganisms may be obtained for physiological investigations. In addition, these techniques allow the quantitative and qualitative assessment of the investigated environment. Quantitative analyses are done by plate count and the determination of abundance by the colony forming unit (CFU). Nevertheless, these techniques have many drawbacks that lead to an underestimation of the cell numbers and do not provide a comprehensive overview of the composition of the inhabiting microbiota. In the last decades, several molecular techniques have been developed enabling many advantages over the cultivation approach. Mainly PCR-based, fingerprinting techniques allow a qualitative detection and identification of the microbiota. In this study, we developed a real time PCR method as a simple, rapid and reliable tool to detect and quantify fungal abundance using the ß-actin gene, which is known to appear as a single-copy gene in fungi. To this end, five different indoor thermal insulation materials applied for historical buildings that were previously tested for their bio-susceptibility against various fungi were subjected to qPCR analyses. The obtained results were compared with those obtained from a previous study investigating the bio-susceptibility of the insulation materials using classical cultivation experiments. Both results correlated well, revealing that Perlite plaster was the most suitable insulation material, showing the lowest fungal CFU and qPCR values. In contrast, insulations made of wood showed to be not recommendable from the microbiological point of view. In addition, the potential of qPCR was tested in other materials of cultural heritage, as old parchments, showing to be a suitable method for measuring fungal abundance in these delicate materials.

Contribution of the microbial communities detected on an oil painting on canvas to its biodeterioration.

In this study, we investigated the microbial community (bacteria and fungi) colonising an oil painting on canvas, which showed visible signs of biodeterioration. A combined strategy, comprising culture-dependent and -independent techniques, was selected. The results derived from the two techniques were disparate. Most of the isolated bacterial strains belonged to related species of the phylum Firmicutes, as Bacillus sp. and Paenisporosarcina sp., whereas the majority of the non-cultivable members of the bacterial community were shown to be related to species of the phylum Proteobacteria, as Stenotrophomonas sp. Fungal communities also showed discrepancies: the isolated fungal strains belonged to different genera of the order Eurotiales, as Penicillium and Eurotium, and the non-cultivable belonged to species of the order Pleosporales and Saccharomycetales. The cultivable microorganisms, which exhibited enzymatic activities related to the deterioration processes, were selected to evaluate their biodeteriorative potential on canvas paintings; namely Arthrobacter sp. as the representative bacterium and Penicillium sp. as the representative fungus. With this aim, a sample taken from the painting studied in this work was examined to determine the stratigraphic sequence of its cross-section. From this information, "mock paintings," simulating the structure of the original painting, were prepared, inoculated with the selected bacterial and fungal strains, and subsequently examined by micro-Fourier Transform Infrared spectroscopy, in order to determine their potential susceptibility to microbial degradation. The FTIR-spectra revealed that neither Arthrobacter sp. nor Penicillium sp. alone, were able to induce chemical changes on the various materials used to prepare "mock paintings." Only when inoculated together, could a synergistic effect on the FTIR-spectra be observed, in the form of a variation in band position on the spectrum.