Lascaux Cave (Montignac, France) contains paintings from the Upper Paleolithic period. Shortly after its discovery in 1940, the cave was seriously disturbed by major destructive interventions. In 1963, the cave was closed due to algal growth on the walls. In 2001, the ceiling, walls and sediments were colonized by the fungus Fusarium solani. Later, black stains, probably of fungal origin, appeared on the walls. Biocide treatments, including quaternary ammonium derivatives, were extensively applied for a few years, and have been in use again since January 2008. The microbial communities in Lascaux Cave were shown to be composed of human-pathogenic bacteria and entomopathogenic fungi, the former as a result of the biocide selection. The data show that fungi play an important role in the cave, and arthropods contribute to the dispersion of conidia. A careful study on the fungal ecology is needed in order to complete the cave food web and to control the black stains threatening the Paleolithic paintings.

The walls and ceiling of Altamira Cave, northern Spain, are coated with different coloured spots (yellow, white and grey). Electron microscopy revealed that the grey spots are composed of bacteria and bioinduced CaCO(3) crystals. The morphology of the spots revealed a dense network of microorganisms organized in well-defined radial and dendritic divergent branches from the central area towards the exterior of the spot, which is coated with overlying spheroidal elements of CaCO(3) and CaCO(3) nest-like aggregates. Molecular analysis indicated that the grey spots were mainly formed by an unrecognized species of the genus Actinobacteria. CO(2) efflux measurements in rocks heavily covered by grey spots confirmed that bacteria-forming spots promoted uptake of the gas, which is abundant in the cave. The bacteria can use the captured CO(2) to dissolve the rock and subsequently generate crystals of CaCO(3) in periods of lower humidity and/or CO(2). A tentative model for the formation of these grey spots, supported by scanning electron microscopy and transmission electron microscopy data, is proposed.

In recent years, methane (CH 4 ) has received increasing scientific attention because it is the most abundant non-CO 2 atmospheric greenhouse gas (GHG) and controls numerous chemical reactions in the troposphere and stratosphere. However, there is much that is unknown about CH 4 sources and sinks and their evolution over time. Here we show that near-surface cavities in the uppermost vadose zone are now actively removing atmospheric CH 4 . Through seasonal geochemical tracing of air in the atmosphere, soil and underground at diverse geographic and climatic locations in Spain, our results show that complete consumption of CH 4 is favoured in the subsurface atmosphere under near vapour-saturation conditions and without significant intervention of methanotrophic bacteria. Overall, our results indicate that subterranean atmospheres may be acting as sinks for atmospheric CH 4 on a daily scale. However, this terrestrial sink has not yet been considered in CH 4 budget balances. M ethane (CH 4 ) is currently the most abundant non-CO 2 greenhouse gas (GHG) in the atmosphere, reaching a global average concentration of B1,800 p.p.b. at midnorthern latitudes 1 . Despite significant research progress in recent years, large uncertainties remain about the CH 4 budget and its evolution over time because there is a lack of knowledge about CH 4 sinks and sources [2][3][4][5] . Superimposed on the long-term trend of increasing atmospheric CH 4 , there is significant interannual variability 1,6,7 , and the sources of variation remain controversial 8 .Current CH 4 estimates account for B22% of the total forcing potential of all long-lived GHGs 9 . By weight, CH 4 is 28 times more effective at trapping heat in the atmosphere than CO 2 over a 100-year period 10 . Sensible mitigation strategies also require a quantitative understanding of the CH 4 budget regarding emissions and sinks 11 . The total global emissions of CH 4 are constrained reasonably well by atmospheric observations and estimates of its lifetime, based on multiple atmospheric CH 4 inversion models (top-down studies). However, the uncertainties concerning emissions/consumption from individual sources/ sinks 12 are greater, and they are poorly constrained by the current atmospheric observation network 6 . Some unaccounted sinks (or sources) could contribute the global CH 4 budget and its long-term variations.The Earth's surface exerts its influence on the free atmosphere through the atmospheric boundary layer. This lowest portion of the atmosphere ranges from a few tens of metres to 1-2-km deep 13 . The subsurface atmosphere is usually overlooked as an important part of this boundary layer. At the top of the subsurface layer in the vadose zone (below the subsoil and above the groundwater table) highly specific biogeochemical processes occur, which may act as regulators of gas exchanges between the surface and the free atmosphere.The uppermost part of the vadose zone may contain large amounts of underground air, that is, a CO 2 -rich air reservoir permeating the unsaturated...

The paintings from Tomba della Scimmia, in Tuscany, are representative of the heavy bacterial colonization experienced in most Etruscan necropolises. The tomb remained open until the late 70′s when it was closed because of severe deterioration of the walls, ceiling and paintings after decades of visits. The deterioration is the result of environmental changes and impacts suffered since its discovery in 1846. We show scanning electron microscopy and molecular studies that reveal the extent and nature of the biodeterioration. Actinobacteria, mainly Nocardia and Pseudonocardia colonize and grow on the tomb walls and this process is linked to the availability of organic matter, phyllosilicates (e.g. clay minerals) and iron oxides. Nocardia is found metabolically active in the paintings. The data confirm the specialization of the genera Nocardia and Pseudonocardia in the colonization of subterranean niches.

Volcanic caves are filled with colorful microbial mats on the walls and ceilings. These volcanic caves are found worldwide, and studies are finding vast bacteria diversity within these caves. One group of bacteria that can be abundant in volcanic caves, as well as other caves, is Actinobacteria. As Actinobacteria are valued for their ability to produce a variety of secondary metabolites, rare and novel Actinobacteria are being sought in underexplored environments. The abundance of novel Actinobacteria in volcanic caves makes this environment an excellent location to study these bacteria. Scanning electron microscopy (SEM) from several volcanic caves worldwide revealed diversity in the morphologies present. Spores, coccoid, and filamentous cells, many with hair-like or knobby extensions, were some of the microbial structures observed within the microbial mat samples. In addition, the SEM study pointed out that these features figure prominently in both constructive and destructive mineral processes. To further investigate this diversity, we conducted both Sanger sequencing and 454 pyrosequencing of the Actinobacteria in volcanic caves from four locations, two islands in the Azores, Portugal, and Hawai'i and New Mexico, USA. This comparison represents one of the largest sequencing efforts of Actinobacteria in volcanic caves to date. The diversity was shown to be dominated by Actinomycetales, but also included several newly described orders, such as Euzebyales, and Gaiellales. Sixty-two percent of the clones from the four locations shared less than 97% similarity to known sequences, and nearly 71% of the clones were singletons, supporting the commonly held belief that volcanic caves are an untapped resource for novel and rare Actinobacteria. The amplicon libraries depicted a wider view of the microbial diversity in Azorean volcanic caves revealing three additional orders, Rubrobacterales, Solirubrobacterales, and Coriobacteriales. Studies of microbial ecology in volcanic caves are still very limited. To rectify this deficiency, the results from our study help fill in the gaps in our knowledge of actinobacterial diversity and their potential roles in the volcanic cave ecosystems.

Despite evidence of damaging human impacts, cave paintings may again be threatened if visitors are allowed access.

In the last few years, the microbial colonisation of mural paintings in ancient monuments has been attracting the attention of microbiologists and conservators. The genus Rubrobacter is commonly found in biodeteriorated monuments, where it has been reported to cause rosy discolouration. However, to date, only three species of this genus have been isolated, all from thermophilic environments. In this paper, we studied three monuments: the Servilia and Postumio tombs in the Roman Necropolis of Carmona (Spain), and Vilar de Frades church (Portugal), in search of Rubrobacter strains. In all cases, biodeterioration and the formation of efflorescences were observed, and five Rubrobacter strains were isolated. These isolates showed different physiology and migration in denaturing gradient gel electrophoresis, suggesting they might represent new species within this genus. The isolates reproduced some biodeterioration processes in the laboratory and revealed their biomediation in crystal formation.

Purpose We investígated the effects of human-induced disruption in a subterranean stable environment containing valuable Palaeolithic paíntings and engravings (Ardales Cave, Southern Spain) using a double analytical approach.