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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. [ABSTRACT FROM AUTHOR]

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.

In this study, two essential oils (EOs) with preventive proved biocidal efficacy, namely oregano and eugenol, are encapsulated in silica nanocontainer, then dispersed in multifunctional, hybrid and nanocomposite coating. The aim of this work is to reduce toxicity of restoration materials, to avoid the chemicals dispersion in the environment and to extent stone protection treatments, preventing biofouling. Composite silica nanocapsules, containing separately the two EOs, are prepared via one-step synthesis, based on oil-in-water miniemulsion polymerisation processes, and fully characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and N 2 physisorption (BET/BJH). Micro-Raman spectroscopy (RS) and thermal analysis (TG/DSC). In a second step, nanocomposite coatings, based on a flexible tetraethyl orthosilicate (TEOS) matrix, are synthesised dispersing TiO 2 nanoparticles and the two silica nanocapsules incorporating EOs. The coatings were applied on three different lithotypes samples of historical importance: brick, piperine and mortar. The effectiveness and compatibility of the coating formulation with the different stone substrates were assessed through a multi-analytical standard protocol. The silica nanocapsules, show monodispersed spherical shape with size ∼110 nm, a core-shell structure, a BET surface area of 600–700 m2/g and high loading capacity. The results on coatings characterisation show a crack-free and transparent structure. Moreover, the tests on applied coatings reveal the high hydrophobicity of the treated stone samples (static contact angle in the range ∼ 130–140° and reduction of liquid water capillary absorption 97–99 %) and unaltered permeability to water vapour (density of water vapour flow rate in the range 150–200 g/m2·d), demonstrating the suitability of the nanocomposite hybrid coatings for the application in stone protection against biodeterioration. [Display omitted] • Nanocomposite hybrid coatings have been synthesised to contrast biodeterioration of stones. • Essential oils are successfully encapsulated in mesoporous core-shell silica nanocapsules. • Nanocapsules and photocatalytic TiO 2 nanoparticles are dispersed in the hybrid polymetric matrix. • Crack-free and transparent coatings are obtained and tested on different stone substrates. • Treated stone surfaces show very high hydrophobicity and unaltered permeability to water vapour. [ABSTRACT FROM AUTHOR]

In the last decade, worldwide research has focused on innovative natural biocides and the development of organic and inorganic nanomaterials for long-lasting reliability. In this work, the biocide effects of two different biocides encapsulated in two different silica nanosystems for a multifunctional coating have been performed through in vitro tests, by using Chlorococcum sp. as a common stone biodeteriogen. Zosteric sodium salt (ZS), a green biocide, was compared with the commercial biocide, 2-mercaptobenzothiazole (MBT), widely used in the treatment of cultural heritage. The analyzed systems are the following: silica nanocapsules (NC) and silica nanoparticles (MNP) not loaded with biocides, two nanosystems loaded with ZS and MBT, and free biocides. The qualitative and quantitative evaluations of biocide efficiency were performed periodically, analyzing pigment autofluorescence to discriminate between active and inactive/dead cells. The analyses showed multiple differences. All the nanocontainers presented an initial reduction in chlorophyll's autofluorescence. For the free biocide, the results highlighted higher efficiency for MBT than ZS. Finally, the nanosystems loaded with the different biocides highlighted a higher activity for nanocontainers loaded with the commercial biocide than the green product, and better efficiency for MNP in comparison with NC. [ABSTRACT FROM AUTHOR]

Biological growth represents one of the main threats for the conservation of subterranean cultural heritage. Knowledge of the conditions which favour the various taxonomic groups is important in delineating their control methods. Combining our experience regarding hypogea in Italy and the Republic of Korea, we aim to perform a critical review and comparison of the Biodeterioration Patterns (BPs) found, the materials used, and the conservative treatments applied. For this purpose, we focused on Etruscan tombs (Italy, 7th to 3th century BC) and the ancient tombs of the Baekje Dynasty (Republic of Korea, 6th to 7th centuries AD), most of which have been designated UNESCO World Heritage Sites, collecting original and bibliographic data as well as official documents. Results highlight the rich biodiversity of the bacterial and fungal species. Phototrophs were observed only in niches with sufficient light and the development of roots was also detected. Changes in humidity and temperature, the nature of the soil, nutrient accumulation, and vegetation above the hypogea along with human activities explain the different BPs. The effects of biocide treatments are also discussed, such as the emergence of dangerous fungal species. The shared data also enhance the role of overlaying tumuli and vegetation as well as protective barriers to reduce biological risk. [ABSTRACT FROM AUTHOR]

In the last decade, worldwide research has focused on innovative natural biocides and the development of organic and inorganic nanomaterials for long-lasting reliability. In this work, the biocide effects of two different biocides encapsulated in two different silica nanosystems for a multifunctional coating have been performed through in vitro tests, by using Chlorococcum sp. as a common stone biodeteriogen. Zosteric sodium salt (ZS), a green biocide, was compared with the commercial biocide, 2-mercaptobenzothiazole (MBT), widely used in the treatment of cultural heritage. The analyzed systems are the following: silica nanocapsules (NC) and silica nanoparticles (MNP) not loaded with biocides, two nanosystems loaded with ZS and MBT, and free biocides. The qualitative and quantitative evaluations of biocide efficiency were performed periodically, analyzing pigment autofluorescence to discriminate between active and inactive/dead cells. The analyses showed multiple differences. All the nanocontainers presented an initial reduction in chlorophyll’s autofluorescence. For the free biocide, the results highlighted higher efficiency for MBT than ZS. Finally, the nanosystems loaded with the different biocides highlighted a higher activity for nanocontainers loaded with the commercial biocide than the green product, and better efficiency for MNP in comparison with NC.

Stone works of art located outdoors are exposed to natural deterioration, due to several physical, chemical and biological factors. Biological macro- and micro-systems (e.g. weeds, insects, algae, mosses, fungi and bacteria) may induce the biodeterioration of stone materials. In February 2014, the state of conservation of the Fountain of the two Dragons in Palermo was examined, during which time biological colonization in some areas of the fountain and statues, was also detected. The monument represents an excellent substrate for the development and growth of microrganisms and organisms that need a continuous supply of water. Direct solar irradiance promotes the development of photoautotrophic organisms, bryophyte flora, in addition to several microbial genera, responsible for pigmentation, discoloring, efflorescence. After autotrophic colonization, some organisms find an ideal habitat also during wintertime, including two species of gastropods and two species of Hemiptera, omnivorous, a species of Collembola, mostly fungivorous. This interdisciplinary study has enabled the detection and identification of different biological communities, providing information for a subsequent project of preventive conservation of the fountain and its surroundings.

Fungi are among the biotic agents that can cause deterioration of building stones and cultural heritage. The most common methods used to control fungal spread and growth are based on chemical pesticides. However, the massive use of these synthetic chemicals produces heavy environmental pollution and risk to human and animal health. Furthermore, their use is time dependent and relies on the repetition of treatments, which increases the possibility of altering building stones and culture heritage through environmental contamination. One alternative is the use of natural products with high antifungal activity, which can result in reduced toxicity and deterioration of archeological remains. Recently, three fungal strains, namely Aspergillus niger, Alternaria alternata and Fusarium oxysporum, were isolated as damaging agents from the external tuff wall of the Roman remains “Villa of Poppea” in Oplontis, Naples, Italy. In this manuscript, three selected fungal metabolites, namely cyclopaldic acid, cavoxin and epi-epoformin, produced by fungi pathogenic for forest plants, were evaluated as potential antifungal compounds against the above fungi. Cavoxin and epi-epoformin showed antifungal activity against Asperigillus niger and Fusarium oxysporum, while cyclopaldic acid showed no activity when tested on the three fungi. The same antifungal activity was observed in vitro experiments on infected stones of the Neapolitan yellow tuff (NYT), a volcanic lithotype widely diffused in the archeological sites of Campania, Italy. This study represents a first step in the use of these two fungal metabolites to allow better preservation of artworks and to guarantee the conditions suitable for their conservation.

• The present paper investigates the use of natural biocides on stone materials. • The dataset collects details on methods and results for each test of each paper. • The most promising substances are highlighted. • Deficiencies and further needs in the use of biocides are evaluated. The use of traditional biocides to reduce bio-deterioration phenomena of stone monuments is increasingly deterred, due to risks for human health and the environment, as well as for potential interference with materials. Extensive research is now ongoing, aiming to find alternative and eco-friendly substances or methods to halt or reduce bio-deterioration. Here we aim to provide an assessment of the results of scientific tests, in order to evaluate the most promising substances, likewise possible deficiencies and future directions in research. We performed an extensive literature review on natural biocides for controlling bio-deterioration of stone using peer-reviewed articles between 1986 and 2018. The dataset created displays information about the experimentation of a total of 61 natural substances, mostly essential oils (23), or substances of plant origin and other compounds. The methods of application of such biocides were diverse, but the in vitro tests were the prevailing ones. The most tested organisms were fungi, followed by cyanobacteria and algae. The efficacy of the substances resulted highly variable, as did protocols and experimental doses, resulting in a lack of a robust and coherent assessment of best practices. Also, we found a few papers discussing the interference of these substances with the substrate. We believe that this area of research is very promising and necessary, although additional tests with a standardised methodology are still needed. [ABSTRACT FROM AUTHOR]

Some of Austria's most important petroglyphs are located in the alpine region of Dachstein, carved in the local limestone. Favored by the humid and shady environment, most of the engravings are covered by extensive biological colonization. In order to assess whether and to what extent the biopatinas present on the stone cause biodeterioration, we investigated their interactions with the rock substrate by microscopy methods (and PAS-staining), in combination with a metagenomic analysis to identify the biofilms' composition. The microscopy methods highlighted a general biodeterioration state of the stone and the great boring ability of the biofilms, especially of those with filamentous cyanobacteria (e.g., Nostocales and Oscillatoriales), and showed that a thick moss biofilm (with high abundance of Bacteroidota taxa) was the most harmful for the stone support, causing severe disruption of the underlying rock. Interestingly, the analysis of stone without visible biofilm revealed a microbiome dominated by ammonia-oxidizing archaea (AOAs), probably indicating the presence of a previous degraded biofilm (source of ammonia), and a current state of deterioration (dissolution of calcium carbonate). Removal of the biopatinas, or their alteration, would expose an already altered surface, potentially giving rise to a new colonization and new cycles of biodeterioration. • Biofilms on petroglyphs were analyzed by optical microscopy, SEM and metagenomics. • PAS staining method was very useful in the visualization of biofilms in the stone. • Thick biofilms with moss seem to be related to a more severe disruption of the rock. • Biofilms penetrate deep into the stone, especially filamentous cyanobacteria. • Stone with no visible biofilm has high abundance of ammonia-oxidizing archaea (AOA). [ABSTRACT FROM AUTHOR]

The safeguarding of Australian outdoor stone heritage is currently limited by a lack of information concerning mechanisms responsible for the degradation of the built heritage. In this study, the bacterial community colonizing the stone surface of an outdoor sculpture located at the Church of St. John the Evangelist in Melbourne was analysed, providing an overview of the patterns of microbial composition associated with stone in an anthropogenic context. Illumina MiSeq 16S rRNA gene sequencing together with confocal laser microscope investigations highlighted the bacterial community was composed of both phototrophic and chemotrophic microorganisms characteristic of stone and soil, and typical of arid, salty and urban environments. Cardinal exposure, position and surface geometry were the most important factors in determining the structure of the microbial community. The North-West exposed areas on the top of the sculpture with high light exposure gave back the highest number of sequences and were dominated by Cyanobacteria. The South and West facing in middle and lower parts of the sculpture received significantly lower levels of radiation and were dominated by Actinobacteria. Proteobacteria were observed as widespread on the sculpture. This pioneer research provided an in-depth investigation of the microbial community structure on a deteriorated artistic stone in the Australian continent and provides information for the identification of deterioration-associated microorganisms and/or bacteria beneficial for stone preservation. • A pioneer study of biofilm on stone heritage in Australia. • Structure, diversity and interactions of biofilms on the outdoor stones was studied. • Community was composed of both phototrophic and chemotrophic bacteria. • Proteobacteria, Actinobacteria and Cyanobacteria were dominant phyla. • Bacterial community was shaped by cardinal exposure, position and surface geometry. [ABSTRACT FROM AUTHOR]

Biological growth represents one of the main threats for the conservation of subterranean cultural heritage. Knowledge of the conditions which favour the various taxonomic groups is important in delineating their control methods. Combining our experience regarding hypogea in Italy and the Republic of Korea, we aim to perform a critical review and comparison of the Biodeterioration Patterns (BPs) found, the materials used, and the conservative treatments applied. For this purpose, we focused on Etruscan tombs (Italy, 7th to 3th century BC) and the ancient tombs of the Baekje Dynasty (Republic of Korea, 6th to 7th centuries AD), most of which have been designated UNESCO World Heritage Sites, collecting original and bibliographic data as well as official documents. Results highlight the rich biodiversity of the bacterial and fungal species. Phototrophs were observed only in niches with sufficient light and the development of roots was also detected. Changes in humidity and temperature, the nature of the soil, nutrient accumulation, and vegetation above the hypogea along with human activities explain the different BPs. The effects of biocide treatments are also discussed, such as the emergence of dangerous fungal species. The shared data also enhance the role of overlaying tumuli and vegetation as well as protective barriers to reduce biological risk.

Biodeterioration of stone monuments is estimated to be as high as 20–30% of the total degradation suffered by Cultural Heritage constructions. With regard to this problem, bactericidal treatments are mainly based on cleaning. These processes, while effective in the short term, require frequent reapplications increasing potential damages to the monument. Silver nanoparticles offer many advantages over traditionally employed products, such as their prolonged biocide efficacy and their low toxicity to humans and environment. The aim of this study was to evaluate the applicability and effectiveness of seven nanocomposite treatments based on titanium dioxide and/or silver nanoparticles to prevent biodeterioration of limestone monuments. These nanocomposites were characterized by UV–Visible spectrophotometry, Dynamic Light Scattering and Electron Microscopy. To assess their bactericidal activity, accelerated weathering tests were performed on limestones from the quarry of Utrera, a source widely employed in such iconic monuments as the Cathedral of Seville (Spain). Furthermore, the samples of biopatina employed in our assays stemmed from the façades of historical buildings from Seville. Our results show that silver and titanium dioxide nanocomposites stabilized by citrate achieve a high biocide effect while maintaining color alterations at a low level. [ABSTRACT FROM AUTHOR]

Identification of microorganisms on the surfaces of historical objects traditionally involves classical microbiology techniques. Cultivation methods allow, to a limited extent, the investigation of microbial biodiversity occurring in the environment. The aim of this study was to select microbiological media, the use of which enables cultivation of bacteria in proportions and diversity most similar to that observed in situ in the microbiocenoses of historical stone objects. We carried out scanning electron microscopy (SEM) imaging, quantitative analysis of microorganisms using culture-dependent methods and high-throughput sequencing of the bacterial communities taken from the surfaces of the Pergola located at the Wilanow Palace gardens in Warsaw (Poland). Total DNA was isolated directly from the collected samples and from the grown colonies of microorganisms grouped together from a particular type of microbiological agar media. Amplification of the V3-V4 region of the 16S rRNA gene for Bacteria was performed for each sample. Illumina MiSeq technology was used for sequencing. Metagenomic analysis of the sequences revealed that the agar Wort medium is the best choice to determine the bacterial diversity present in situ in the biocenoses grown on historical sandstone surfaces. [ABSTRACT FROM AUTHOR]

The aim of the present study was to analyze the epilithic bacterial diversity of the ruins of the Chaalis Abbey, France. To do this, stone samples were collected at the surface of three areas presenting different macroscopic characteristics: a Discolored Area (DCA), a Damaged Area (DMA) and an Undamaged Area (UDMA). The bacterial diversity investigation after DNA extraction and amplified ribosomal DNA restriction analysis targeting the 16S rRNA genes revealed that clone libraries were dominated by Alphaproteobacteria and Actinobacteria . The main part of recovered phylotypes belonged to genera previously associated with stone colonization and/or biodeterioration. Indeed most abundant Alphaproteobacteria phylotypes belonged to the genus Sphingomonas and to the species Bosea thiooxidans , and most abundant Actinobacteria phylotypes belonged to the genera Rubrobacter and Arthrobacter . Members of Cyanobacteria , Bacteroidetes , TM7, Betaproteobacteria , Deinococcus , Acidobacteria and Chloroflexi were also recovered but to a lesser extent. In conclusion, these results suggest that the ruins of the Chaalis Abbey are covered by bacterial communities mainly composed of Alphaproteobacteria and Actinobacteria able to colonize and, for some of them, to deteriorate stone. [ABSTRACT FROM AUTHOR]

In this study exfoliated sandstone samples from Portchester Castle were investigated using scanning electron microscopy (SEM) and energy dispersion X-ray (EDX) analyses to observe stone surface colonisation, geomorphological structure and to assess damage. Archaeal and bacterial diversity were assessed using cultivation-dependent and cultivation-independent methods. SEM analysis showed that sandstone had high levels of stone decay. There was considerable weathering of the minerals associated with biofilms containing microbes with various cellular morphologies. Microorganisms were especially prevalent in pores, cavities and in the heavily decayed parts of the minerals, and some etching was seen. EDX analyses indicated microbes were associated with the sheet structures of aluminium-containing phyllosilicate minerals, most likely glauconite. Microbial colonisation was preferentially concentrated within specific sheets of the mineral structure. Isolation studies revealed the presence of Bacillus and Arthrobacter that appeared to be well adapted to “extreme” environments, specifically these isolates were tolerant to high salt, high UV and oligotrophic conditions. Cultivation-independent studies using denaturing gradient gel electrophoresis fingerprinting of bacterial and archaeal 16S rRNA gene fragments showed a more complex community. Chloroflexi, Actinobacteria, Deinococcus , α- and β-proteobacteria, Cyanobacteria and Bacteroidetes and halophilic Archaea from the family Halobacteriaceae, were the predominant types of Bacteria and Archaea detected respectively. [ABSTRACT FROM AUTHOR]

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Various biological communities colonize the Khmer temples in Angkor (Cambodia), which had lain abandoned for many centuries. These biodeterioration patterns change in response to different environmental conditions, and the aim of this study is to quantify their frequency and ecological characteristics according to a forest canopy gradient. The descriptive and multivariate statistical analysis applied to data collected from the four temples in the study identifies various biological communities along with a temple-specific ecological succession. The initial pioneer community is primarily composed of a reddish biofilm of the green alga Trentepohlia sp., and it occurs in xeric and shady environmental conditions, becoming dominant in forested areas. Cyanobacteria biofilm, consisting of species belonging to the genera Scytonema and Gloeocapsa , sometimes in combination with the lichen Endocarpon sp., prevails in xeric and sunny conditions. With the progressive increase of the availability of edaphic water, typical of forested areas, various lichen communities are able to establish themselves (dominated by Lepraria , Pyxine coralligera and Cryptothecia subnidulans respectively), followed by moss and higher plant communities. Understanding these relationships appears to be a very useful way of identifying the best microclimatic conditions for stone conservation. [ABSTRACT FROM AUTHOR]

Microbial colonization has a relevant impact on the deterioration of stone materials with consequences ranging from esthetic to physical and chemical changes. Avoiding microbial growth on cultural stones therefore represents a crucial aspect for their long-term conservation. The antimicrobial properties of silver nanoparticles (AgNPs) have been extensively investigated in recent years, showing that they could be successfully applied as bactericidal coatings on surfaces of different materials. In this work, we investigated the ability of AgNPs grafted to Serena stone surfaces to inhibit bacterial viability. A silane derivative, which is commonly used for stone consolidation, and Bacillus subtilis were chosen as the grafting agent and the target bacterium, respectively. Results show that functionalized AgNPs bind to stone surface exhibiting a cluster disposition that is not affected by washing treatments. The antibacterial tests on stone samples revealed a 50 to 80 % reduction in cell viability, with the most effective AgNP concentration of 6.7 μg/cm. To our knowledge, this is the first report on antimicrobial activity of AgNPs applied to a stone surface. The results suggest that AgNPs could be successfully used in the inhibition of microbial colonization of stone artworks. [ABSTRACT FROM AUTHOR]

Abstract: Despite the wide spectrum of literature on stone biodeterioration associated with pitting, there has not been sufficient description of some general topics related to stone biopitting in terrestrial conditions, nor of the taxonomy of the organisms supporting it. In order to synthesize the information available in the literature, and to give a critical analysis of the bibliographic data, an interactive on-line database has been created. Among the about 800 papers selected in the first step of creating this database. Only 24 studies reported on biopitting, giving information on the object, material composition and associated organisms. These first data concern 83 different sites, for a total of 249 samples, coming mainly from the Mediterranean bioclimatic area, even though the biopitting phenomenon is not exclusive to this climate. The most commonly occurring organisms are cyanobacteria, and the associated environmental conditions are dryness, arising from various factors, such as the low porosity of the stone; the exposure conditions; and the bioclimate. These factors explain very high appearance of organisms and especially cyanobacteria in marble, their preference for vertical or subvertical surfaces, and their high occurrence in Mediterranean and desert climate. The lack of information describing the entire phenomenon i.e., type of stone, exposure conditions, and all biodeteriogens present, doesn''t permit the full use of the database''s interactive potential. [Copyright &y& Elsevier]

Abstract: This study analyses the plant colonization of the stone embankments along the Tiber River (the Lungotevere) in relation to changes of lithotype (travertine, tuff, cement), inclination (80°, 60°, 45°), stone size, and exposure. The surveys of plant communities were carried out according to the phytosociological method and considering the variability of the ecological conditions. The vegetation data were analyzed using multivariate statistical analysis (cluster analysis) in order to highlight the affinity among the various groups of sampling areas. The ecological features of the vegetation, according to Ellenberg indicator values, were considered for the ecological interpretation. Results showed that many environmental factors interact in giving rise to a differential plant cover and species richness, but that some are more relevant than others, such as the lithotype nature, especially in relation to the differential stone porosity. Also, changes in inclination of the walls cause variations in plant colonization, especially in the case of travertine and less in the case of tuff, as a consequence of the differing porosity of these materials. The study also confirms the subordinate role of exposure with respect to other factors. [Copyright &y& Elsevier]

A survey of studies on the structure and functioning of sub-aerial epilithic phototrophic biofilms, which develop inside hypogea sites, was conducted in the framework of projects whose aim is to investigate cyanobacteria and associated microorganisms causing deterioration of stone artefacts. Using different methodological approaches, it was possible to identify and characterize cyanobacterial taxa, and to deduce their relationships with other microorganisms and the mineral substrata. Part of studies also aimed at identifying biotransformation and biomineralization mechanisms affecting stone, and the biofilm response to various light conditions. The calcium distribution and the structure of the cyanobacterial sheath gave an indication on the most deteriogenic species. Monochromatic light experiments allowed us to develop non-destructive methodological approaches for the monitoring and control/prevention of cyanobacterial biofilm growth on stone. [ABSTRACT FROM AUTHOR]

The distribution and amount of biological colonisation on the “Lungotevere” walls (Rome) were analysed to assess the ecological role of the main environmental parameters (solar irradiation, rain winds, prevailing winds) and of the nearby tree covering. The floral data indicate a close similarity of species in the stations examined and a dominance of Chroococcus lithophilus Ercegovic among the cyanobacteria and of Erigeron karvinskianus DC among the vascular plants. In these very hard conditions the exposure and amount of the water input do not seem to influence the flora qualitatively as much as it does quantitatively. The low value of microflora, as found in areas characterised by the presence of trees, can be referred to as resulting from the “umbrella” effect of the plants. The macroflora is less influenced by such effects due to the greater capacity of these plants to derive moisture through their roots. [Copyright &y& Elsevier]

Fungi are among the biotic agents that can cause deterioration of building stones and cultural heritage. The most common methods used to control fungal spread and growth are based on chemical pesticides. However, the massive use of these synthetic chemicals produces heavy environmental pollution and risk to human and animal health. Furthermore, their use is time dependent and relies on the repetition of treatments, which increases the possibility of altering building stones and culture heritage through environmental contamination. One alternative is the use of natural products with high antifungal activity, which can result in reduced toxicity and deterioration of archeological remains. Recently, three fungal strains, namely Aspergillus niger, Alternaria alternata and Fusarium oxysporum, were isolated as damaging agents from the external tuff wall of the Roman remains "Villa of Poppea" in Oplontis, Naples, Italy. In this manuscript, three selected fungal metabolites, namely cyclopaldic acid, cavoxin and epi-epoformin, produced by fungi pathogenic for forest plants, were evaluated as potential antifungal compounds against the above fungi. Cavoxin and epi-epoformin showed antifungal activity against Asperigillus niger and Fusarium oxysporum, while cyclopaldic acid showed no activity when tested on the three fungi. The same antifungal activity was observed in vitro experiments on infected stones of the Neapolitan yellow tuff (NYT), a volcanic lithotype widely diffused in the archeological sites of Campania, Italy. This study represents a first step in the use of these two fungal metabolites to allow better preservation of artworks and to guarantee the conditions suitable for their conservation. [ABSTRACT FROM AUTHOR]

Ailanthus altissima is an extremely aggressive and globally invasive species. This tree has ideal growing conditions in ruderal areas, and is difficult to manage, as cutting is a trigger for the sprouting of new suckers. Despite the wide literature on the negative impacts of this species, measurements of its interaction with archaeological monuments are lacking. We analyzed its colonization behavior and the caused damages along the Aurelian Walls in Rome, which resulted in detachments, crackings and deformation. Our results highlighted the rapid growth potential and wide distribution of this tree in the site (48 nuclei with 578 stems, mainly root suckers, along 7.1 km of 12.5 total length). Our study also provides a quantitative assessment of the damaging potential of A. altissima , as, in 16 out of 48 nuclei, we detected visible damage to the walls, which were likely due to both mechanical and chemical interactions through acidic exudates. The damages correlated significantly with plant size but not with plant distance from the walls, likely due to the wide lateral spread of the roots. This work highlighted the need to monitor and contain A. altissima , but also offers a general approach for the assessment of risks to monuments by higher plants. Image 1 • Ailanthus altissima is an invasive species often growing in archaeological sites. • A. altissima can damage structures through mechanical and chemical action. • We analyze the growth and spreading of this species along the Aurelian Walls (Rome). • We analyze and quantify the damages it induces on these walls defining a risk map. • We give a methodological contribution in the valuation of damage risk due to plants. [ABSTRACT FROM AUTHOR]

The colonisation of stone by different organisms often leaves biodeterioration patterns (BPs) on the surfaces even if their presence is no longer detectable. Peculiar weathering patterns on monuments and rocks, such as pitting phenomena, were recognised as a source of information on past colonisers and environmental conditions. The evident inhibition areas for new bio-patinas observed on the marble blocks of the Caestia Pyramid in Rome, recognisable as tracks of previous colonisations, seem a source for developing new natural products suitable for restoration activities. To hypothesise past occurring communities and species, which gave rise to such BPs, we carried out both in situ observations and analyses of the rich historical available iconography (mainly photographs). Moreover, we analysed literature on the lichen species colonising carbonate stones used in Roman sites. Considering morphology, biochemical properties and historical data on 90 lichen species already reported in Latium archaeological sites, we suppose lichen species belonging to the genus Circinaria (Aspicilia s.l.) to be the main aetiological agent of such peculiar BPs. These results seem relevant to highlight the long-lasting allelopathic properties of some lichen substances potentially applicable as a natural product to control colonisation, improving the environmental and economical sustainability of stone restoration. [ABSTRACT FROM AUTHOR]

Rosy discoloration has affected the stone steps in the main spiral staircase of the Sully-sur-Loire castle donjon for many years now. This study monitors the development of the coloration and the environmental climatic conditions in the staircase to understand the conditions favoring the presence of this rosy discoloration. High-throughput sequencing was performed on healthy stone and on pink pigmented stone to identify the agent responsible for this discoloration. The results suggest that the rosy discoloration is the mark of a former degradation process which is now inactive, and that bacteria were the main agent of the pink patina formation. Nitiliruptor was the main genus identified in the pink parts of the staircase. This is the first time that this bacterial genus has been linked to a cultural heritage biodeterioration process. There was no evidence that this bacterial genus was responsible for the development of the pink patina, but it could have replaced it as a subsequent evolution of the process. • Monitoring of the rosy discoloration of stones. • Although still visible, the discolouration process now appears to be inactive. • The rosy discoloration of stones was caused by bacterial development. • Next-gen sequencing revealed Nitriliruptor to be the main genus on discolored stones. • Nitriliruptor may have replaced the agent initially responsible for the discoloration. [ABSTRACT FROM AUTHOR]

More recently, the biological colonization of stone heritage and consequently its biodeterioration has become the focus of numerous studies. Among all microorganisms, fungi are considered to be one of the most important colonizers and biodegraders on stone materials. This is why the development of new antifungal materials requires immediate action. ZnMgO nanoparticles (NPs) have several exciting applications in different areas, highlighting as an efficient antimicrobial agent for medical application. In this research, the application of Zn-doped MgO (Mg 1-x Zn x O, x = 0.096) NPs obtained by sol-gel method as antifungal coatings on dolomitic and calcitic stones has been explored as a means to develop effective protective coatings for stone heritage. Moreover, the photocatalytic and antifungal activity of Mg 1-x Zn x O NPs were comparatively studied with single ZnO and MgO NPs. Thus, compared to the MgO and ZnO nanomaterials, the Mg 1-x Zn x O NPs exhibited an enhanced photocatalytic activity. After UV irradiation for 60 min, 87% methylene blue was degraded over Zn-doped MgO NPs, whereas only 58% and 38% of MB was degraded over ZnO and MgO NPs, respectively. These nanoparticles also displayed a better antifungal activity than that of single pure MgO or ZnO NPs, inhibiting the growth of fungi Aspergillus niger, Penicillium oxalicum, Paraconiothyrium sp., and Pestalotiopsis maculans, which are especially active in the bioweathering of stone. The improved photocatalytic and antifungal properties detected in the Mg 1-x Zn x O NPs was attributed to the formation of crystal defects by the incorporation of Zn into MgO. The application of the MgO- and Zn-doped MgO NPs as protective coatings on calcareous stones showed important antifungal properties, inhibiting successfully the epilithic and endolithic colonization of A. niger and P. oxalicum in both lithotypes, and indicating a greater antifungal effectiveness on Zn-doped MgO NPs. The use of Zn-doped MgO NPs may thus represent a highly efficient antifungal protection for calcareous stone heritage.