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UNESCO defines cultural heritage as “the legacy of physical artefacts and intangible attributes of a group or society that are inherited from past generations, maintained in the present and bestowed for the benefit of future generations”. The roots of each country and region are anchored in its own cultural heritage. Cultural heritage is an invaluable legacy and is integral to our future, but due to its fragile and finite nature we sought to identify the best, most sustainable means of preserving cultural heritage. This implies the conservation of movable (paintings, sculptures, artifacts) and immovable (monuments, archaeological sites, industrial archaeology) properties. Today, cultural heritage is exposed to air pollution, flooding, earthquakes, wrong management activities, etc., which threaten its integrity. To mitigate damages, research should focus on analyzing and alleviating deterioration and provide technological solutions for enhancing the conservation of cultural heritage. These goals can be achieved through interdisciplinary and transdisciplinary studies. This Special Issue on Interdisciplinary Researches for Cultural Heritage Conservation in Applied Sciences aims to bring together some of the latest researches in this field. A total of 10 papers focusing on different aspects of cultural heritage are categorized into the three topics detailed below and summarized.

European caves contain some of the world’s greatest Paleolithic paintings, and their conservation is at risk due to the use of artificial lighting. Both lighting and high CO2 promotes the growth of phototrophic organisms on walls, speleothems and ground sediments. In addition, the combined effect of increases in CO2, vapor concentration and temperature variations induced by visitors can directly affect the development of corrosion processes on the cave rock surfaces. An early detection of the occurrence of phototrophic biofilms on Paleolithic paintings is of the utmost importance, as well as knowing the microorganisms involved in the colonization of rocks and walls. Knowledge of the colonizing species and their ecology will allow the adoption of control measures. However, this is not always possible due to the limited amount of biomass available for molecular analyses. Here, we present an alternative approach to study faint green biofilms of Chlorophyta in the initial stage of colonization on the Polychrome Panel in El Castillo Cave, Cantabria, Spain. The study of the biofilms collected on the rock art panel and in the ground sediments revealed that the lighting of the cave promoted the development of the green algae Jenufa and Coccomyxa, as well as of complex prokaryotic and eukaryotic communities, including amoebae, their endoparasites and associated bacteria and fungi. The enrichment method used is proposed as a tool to overcome technical constraints in characterizing biofilms in the early stages, allowing a preliminary characterization before deciding for direct or indirect interventions in the cave.

Show caves have different grades of colonization by phototrophic biofilms. They may receive a varied number of visits, from a few thousand to hundreds of thousands of visitors annually. Among them, Tesoro Cave, Rincon de la Victoria, Spain, showed severe anthropic alterations, including artificial lighting. The most noticeable effect of the lighting was the growth of a dense phototrophic community of cyanobacteria, algae and bryophytes on the speleothems, walls and ground. The biofilms were dominated by the cyanobacterium Phormidium sp., the chlorophyte Myrmecia israelensis, and the rhodophyte Cyanidium sp. In many cases, the biofilms also showed an abundance of the bryophyte Eucladium verticillatum. Other cyanobacteria observed in different biofilms along the cave were: Chroococcidiopsis sp., Synechocystis sp. and Nostoc cf. edaphicum, the green microalgae Pseudococcomyxa simplex, Chlorella sp. and the diatom Diadesmis contenta. Preliminary cleaning tests on selected areas showed the effectiveness of hydrogen peroxide and sodium hypochlorite. A physicochemical treatment involving the mechanical removal of the thickest layers of biofilms was followed by chemical treatments. In total, 94% of the surface was cleaned with hydrogen peroxide, with a subsequent treatment with sodium hypochlorite in only 1% of cases. The remaining 5% was cleaned with sodium hypochlorite in areas where the biofilms were entrapped into a calcite layer and in sandy surfaces with little physical compaction. The green biofilms from the entire cave were successfully cleaned.

Mines, like other subterranean environments, have ecological conditions which allow the thriving of microorganisms. Prokaryotes and fungi are common inhabitants of mines, developing a metabolism suitable for growing in such inhospitable environments. The mine of Lousal, Portugal, is an interesting site for the study of microorganisms present in their galleries. Aerobiological studies resulted in the isolation of a Pseudomonas sp., strain L5B5, closely related to the opportunistic fish pathogen P. piscis MC042T, and to the soil bacteria P. protegens CHA0T, P. protegens Cab57, and P. protegens Pf-5. Strain L5B5 was able to inhibit the growth of the pathogenic bacteria Bacillus cereus, Staphylococcus aureus, and Acinetobacter baumanii, as well as the cave fungi Aspergillus versicolor, Penicillium chrysogenum, Cladosporium cladosporioides, Fusarium solani, and Ochroconis lascauxensis. In silico analyses based on de novo genome hybrid assembly and RNA-Seq, performing seven conditions based on culture and phases of growth resulted in the prediction and detection of genetic mechanisms involved in secondary metabolites, with the presence of a possible new gene cluster transcribed under the tested conditions, as well as feasible virulence factors and antimicrobial resistance mechanisms

The genus Crossiella contains two species, C. equi, causing nocardioform placentitis in horses, and C. cryophila, an environmental bacterium. Apart from C. equi, which is not discussed here, environmental Crossiella is rarely reported in the literature; thus, it has not been included among "rare actinobacteria", whose isolation frequency is very low. After C. cryophila, only five reports cover the isolation of Crossiella strains. However, the frequency of published papers on environmental Crossiella has increased significantly in recent years due to the extensive use of next-generation sequencing (NGS) and a huge cascade of data that has improved our understanding of how bacteria occur in the environment. In the last five years, Crossiella has been found in different environments (caves, soils, plant rhizospheres, building stones, etc.). The high abundance of Crossiella in cave moonmilk indicates that this genus may have an active role in moonmilk formation, as evidenced by the precipitation of calcite, witherite, and struvite in different culture media. This review provides an overview of environmental Crossiella, particularly in caves, and discusses its role in biomineralization processes and bioactive compound production.

“Rare actinobacteria” are non-Streptomyces actinobacteria whose isolation frequency is much lower than Streptomyces strains, commonly isolated by conventional methods [1][2]. Tiwari and Gupta [3][4] reported 120 new genera of “rare actinobacteria” in the first decade of the 21th century. A total of 40 out of 120 genera were isolated from soils, with comparatively lower percentages from other environments: marine and freshwater sediments, marine animals, plants, buildings, etc. A few reports included the rare genera Actinomadura, Nonomuraea, Micromonospora, Streptosporangium, Nocardiopsis, and Pseudonocardia as the most frequent in diverse environments [5][6][7][8][9]. It is noteworthy an abundance of “rare actinobacteria” in extreme environments, as exemplified in Atacama [7] and other deserts [10][11][12][13]. However, Crossiella has not been included among “rare actinobacteria” thus far. Researchers have found that Crossiella is an abundant genus in most studied Spanish caves, whether they are gypsum, karstic or volcanic [14][15][16][17][18][19][20][21], and in other terrestrial and aquatic environments., Texto completo disponible en: https://encyclopedia.pub/entry/45605

Nerja Cave, Southern Spain, was revealed as an important biodiversity reservoir from which several novel species of Aspergillus were described. We carried out an aerobiological study in Nerja Cave to assess the origin of airborne fungi. This study quantified the fungi present in the air of ten representative halls covering the three sectors comprising the cave: Touristic Galleries, High Galleries, and New Galleries. Microclimatological monitoring allowed us to understand the dynamic of airborne fungi in two seasons of the year (winter and summer), corresponding to the strongest and the lowest cave ventilation, and to validate the influence that the transport of airborne fungi from outside may have on the cave itself. The data show that cold air enters in winter, as confirmed by the abundant presence of Aspergillus and Penicillium spores inside and outside the cave. In summer, the abundance of some fungi in the air of Nerja Cave, which are not detected outside, indicates a stagnation or low ventilation, and therefore, the concentration of fungal spores is maxima. The high occurrence of Cladosporium outside the cave and the scarce abundance inside support the cave stagnation in this season.

The aerobiology of caves in Southern Spain possesses special characteristics, different from caves located in Northern Spain. Previous studies demonstrated the influence of outdoor air on caves in the north and the existence of two different patterns, depending on the season. In summer there is an abundance of Ascomycota, whereas in winter Basidiomycota predominates, which are related to the periods of stagnation and ventilation, respectively. In caves in Southern Spain the presence of airborne Basidiomycota is scarce and Ascomycota represents the main group of fungi widely distributed across the caves in all seasons. The most characteristic features were the abundant presence of entomopathogenic fungi (Beauveria bassiana, Parengyodontium album, Pochonia chlamydosporia, Leptobacillium symbioticum, Leptobacillium leptobactrum) and Cladosporium cladosporioides in Cueva del Tesoro, Cueva de Ardales and Gruta de las Maravillas. However, the presence of yeasts of the genera Cutaneotrichosporon, Trichosporon, Cryptococcus, Naganishia, Cystobasidium, Microstroma and Phragmotaenium was exclusive to Gruta de las Maravillas. Fungal hazard in the three show caves were determined using an ecological indicator based on the concentration of spores in cave air. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Analytical pyrolysis is a tool widely used for investigating the nature of macromolecules. This technique has been applied with success for solving the chemical structure of geo- and biopolymers. However, with complex macromolecules, such as fungal melanins, analytical pyrolysis presents some drawbacks due to the fact that they rarely can be obtained in a pure grade and contains a mixture of polysaccharides, chitin, proteins, nucleic acids, and lipids, among other materials. Analytical pyrolysis permits the characterization of the compounds co-extracted or linked to the melanin. Nevertheless, our data revealed that under the conditions usually employed in the pyrolysis of melanins, the technique presented serious limitations due to the complex structure and diversity of components that suffer extensive thermal degradation through secondary reactions with the production of considerable number of artifacts. To the light of pyrolysis data, the melanin of Ochroconis spp. is not based on 3,4-dihydroxyphenylalanine (DOPA) or 1,8-dihydroxynaphthalene (DHN), and it is suggested that it could be a type of pyomelanin, based on the polymerization of homogentisic acid and other phenolic compounds.

The Salón de Reinos, a remnant of the 17th century Palacio del Buen Retiro, was built as a recreational residence under the reign of Felipe IV between 1632 and 1640 and was the main room for the monarch’s receptions. This Salón owes its name to the fact that the coats of arms (shields) of the 24 kingdoms that formed Spain in Felipe IV’s time were painted on the vault, above the windows. In addition, the ceiling shows an original decorative composition. The painted ceiling and window vaults showed deterioration evidenced by fissures, water filtration, detachments of the paint layer, and black stains denoting fungal colonization related to humidity. Ten strains of bacteria and 14 strains of fungi were isolated from the deteriorated paintings. Their biodeteriorative profiles were detected through plate assays. The most frequent metabolic functions were proteolytic and lipolytic activities. Other activities, such as the solubilization of gypsum and calcite and the production of acids, were infrequent among the isolates.

Understanding the dynamics and spatial distribution of gases in the subterranean atmospheres is essential to increase the reliability of carbon balances in karst ecosystems or the paleoclimate reconstructions based on cave deposits. This scientific information is also very valuable for cave managers to ensure the safety of visitors and the conservation of the subterranean heritage. Through a comprehensive monitoring of the main air parameters in a shallow temperate cave, we decipher the physical drivers and mechanisms involved in the CO2 and radon exchange between the cave and the outer atmosphere, and how this process is triggered by the changes of local weather. Our results reveal that the biphasic infiltration (water plus air) in the network of penetrative structures from the overlying soil and host rock exercise remarkable control over the cave environment, delaying the thermal response of the cave air to the outer climate-driven changes and also the gaseous transfer between the cave atmosphere and the exterior. The cave location concerning the karstified outcrop determines that this subterranean site acts as a gas emitter during summer, which is contrary to what happens in many other caves. Prominent gas entrapment at a micro-local level is also registered in some upper galleries.

The Cross of the Inquisition, sculpted in 1903 and raised on a column with a fluted shaft and ornamented with vegetable garlands, is located in a corner of the Plateresque façade of the Seville City Hall. The Cross was vandalized in September 2019 and the restoration concluded in September 2021. A geological and microbiological study was carried out in a few small fragments. The data are consistent with the exposure of the Cross of the Inquisition to an urban environment for more than 100 years. During that time, a lichen community colonized the Cross and the nearby City Hall façades. The lichens, bryophytes and fungi colonizing the limestone surface composed an urban community, regenerated from the remains of the original communities, after superficial cleaning of the limestone between 2008 and 2010. This biological activity was detrimental to the integrity of the limestone, as showed by the pitting and channels, which evidence the lytic activity of organisms on the stone surface. Stone consolidation was achieved with Estel 1000. Preventol RI80, a biocide able to penetrate the porous limestone and active against bacteria, fungi, lichens, and bryophytes, was applied in the restoration.

European caves contain some of the world¿s greatest Paleolithic paintings, and their conservation is at risk due to the use of artificial lighting. Both lighting and high CO2 promotes the growth of phototrophic organisms on walls, speleothems and ground sediments. In addition, the combined effect of increases in CO2, vapor concentration and temperature variations induced by visitors can directly affect the development of corrosion processes on the cave rock surfaces. An early detection of the occurrence of phototrophic biofilms on Paleolithic paintings is of the utmost importance, as well as knowing the microorganisms involved in the colonization of rocks and walls. Knowledge of the colonizing species and their ecology will allow the adoption of control measures. However, this is not always possible due to the limited amount of biomass available for molecular analyses. Here, we present an alternative approach to study faint green biofilms of Chlorophyta in the initial stage of colonization on the Polychrome Panel in El Castillo Cave, Cantabria, Spain. The study of the biofilms collected on the rock art panel and in the ground sediments revealed that the lighting of the cave promoted the development of the green algae Jenufa and Coccomyxa, as well as of complex prokaryotic and eukaryotic communities, including amoebae, their endoparasites and associated bacteria and fungi. The enrichment method used is proposed as a tool to overcome technical constraints in characterizing biofilms in the early stages, allowing a preliminary characterization before deciding for direct or indirect interventions in the cave.

Of the several critical challenges present in environmental microbiology today, one is the assessment of the contribution of microorganisms in the carbon cycle in the Earth-climate system. Karstic subterranean ecosystems have been overlooked until recently. Covering up to 25% of the land surface and acting as a rapid CH4 sink and alternately as a CO2 source or sink, karstic subterranean ecosystems play a decisive role in the carbon cycle in terms of their contribution to the global balance of greenhouse gases. Recent data indicate that microbiota must play a significant ecological role in the biogeochemical processes that control the composition of the subterranean atmosphere, as well as in the availability of nutrients for the ecosystem. Nevertheless, there are still essential gaps in our knowledge concerning the budgets of greenhouse gases at the ecosystem scale and the possible feedback mechanisms between environmental-microclimatic conditions and the rates and type of activity of microbial communities in subterranean ecosystems. Another challenge is searching for bioactive compounds (antibiotics) used for treating human diseases. At present, there is a global health emergency and a strong need for novel biomolecules. In recent decades, great research efforts have been made to extract antibiotics from marine organisms. More recently, caves have been receiving considerable attention in search of novel antibiotics. Cave methanotrophic and heterotrophic bacteria are producers of bioactive compounds and may be potential sources of metabolites with antibacterial, antifungal or anticancer activities of interest in pharmacological and medical research, as well as enzymes with a further biotechnological use. Here we also show that bacteria isolated from mines, a still unexplored niche for scientists in search of novel compounds, can be a source of novel secondary metabolites

The Galapagos Islands (Ecuador) have a unique ecosystem on Earth due to their outstanding biodiversity and geological features. This also extends to their subterranean heritage, such as volcanic caves, with plenty of secondary mineral deposits, including coralloid-type speleothems and moonmilk deposits. In this study, the bacterial communities associated with speleothems from two lava tubes of Santa Cruz Island were investigated. Field emission scanning electron microscopy (FESEM) was carried out for the morphological characterization and detection of microbial features associated with moonmilk and coralloid speleothems from Bellavista and Royal Palm Caves. Microbial cells, especially filamentous bacteria in close association with extracellular polymeric substances (EPS), were abundant in both types of speleothems. Furthermore, reticulated filaments and Actinobacteria-like cells were observed by FESEM. The analysis of 16S rDNA revealed the presence of different bacterial phylotypes, many of them associated with the carbon, nitrogen, iron and sulfur cycles, and some others with pollutants. This study gives insights into subsurface microbial diversity of the Galapagos Islands and further shows the interest of the conservation of these subterranean geoheritage sites used as show caves

Cyanobacteria and microalgae are usually found in speleothems, rocks and walls of show caves exposed to artificial lighting. These microorganisms develop as biofilms coating the mineral surfaces and producing aesthetic, physical and chemical deterioration. A wide number of physical, chemical and environmental-friendly methods have been used for controlling the biofilms with different results. Natural biological control has been suggested by some authors as a theoretical approach but without direct evidence or application. Here we report the finding of a natural biological control of phototrophic biofilms on the speleothems of Nerja Cave, Malaga, Spain. The formation of plaques or spots where the phototrophic microorganisms disappeared can be assumed on the basis of processes of predation of bacteria, amoebas and some other organisms on the phototrophic biofilms. This study aims at investigating the potentialities of the biological control of phototrophic biofilms in caves, but the originality of these data should be confirmed in future studies with a larger number of biofilm samples in different ecological scenarios.