Sergio Sanchez-Moral

Paleobiology and comparative morphology of a late Neandertal sample from El Sidrón, Asturias, Spain

Fossil evidence from the Iberian Peninsula is essential for understanding Neandertal evolution and history. Since 2000, a new sample ≈43,000 years old has been systematically recovered at the El Sidrón cave site (Asturias, Spain). Human remains almost exclusively compose the bone assemblage. All of the skeletal parts are preserved, and there is a moderate occurrence of Middle Paleolithic stone tools. A minimum number of eight individuals are represented, and ancient mtDNA has been extracted from dental and osteological remains. Paleobiology of the El Sidrón archaic humans fits the pattern found in other Neandertal samples: a high incidence of dental hypoplasia and interproximal grooves, yet no traumatic lesions are present. Moreover, unambiguous evidence of human-induced modifications has been found on the human remains. Morphologically, the El Sidrón humans show a large number of Neandertal lineage-derived features even though certain traits place the sample at the limits of Neandertal variation. Integrating the El Sidrón human mandibles into the larger Neandertal sample reveals a north–south geographic patterning, with southern Neandertals showing broader faces with increased lower facial heights. The large El Sidrón sample therefore augments the European evolutionary lineage fossil record and supports ecogeographical variability across Neandertal populations.

On the origin of fiber calcite crystals in moonmilk deposits

In this study, we show that moonmilk subaerial speleothems in Altamira Cave (Spain) consist of a network of fiber calcite crystals and active microbial structures. In Altamira moonmilks, the study of the typology and distribution of fiber crystals, extracellular polymeric substances, and microorganisms allowed us to define the initial stages of fiber crystal formation in recent samples as well as the variations in the microstructural arrangement in more evolved stages. Thus, we have been able to show the existence of a relationship among the different types of fiber crystals and their origins. This allowed us to outline a model that illustrates the different stages of formation of the moonmilk, developed on different substrata, concluding that microbes influence physicochemical precipitation, resulting in a variety of fiber crystal morphologies and sizes.

Geomicrobiological Study of the Grotta dei Cervi, Porto Badisco, Italy

Speleothems (active stalactites, wall concretions), rock walls, ceiling, and soils from the galleries of Grotta dei Cervi, Porto Badisco, Italy, were sampled to investigate the culturable heterotrophic microbial communities present in this cave. Sampling was carried out in a transect of about 230 m from the entrance to the central gallery where numerous Gram-positive bacteria were isolated from all studied sites. Members of the genera Agromyces, Arthrobacter, Rhodococcus , and particularly Streptomyces , of the order Actinomycetales, are spread throughout the whole cave. The ability of actinomycetes, and particularly of Nocardiopsis , to colonize salt-stressed environments is favored by the presence of ectoine, a compatible solute for osmotic adaptation. Selected actinomycete isolates were tested for the formation of crystals. Strains from all tested genera, except isolates of Gordonia and Nocardia , produced vaterite and/or calcite. Production of Mgcalcite was restricted to strains of Brachybacterium, Rhodococcus , and Streptomyces , whereas struvite was only precipitated by an unidentified isolate. These findings indicate that actinomycetes may play a role in the formation of mineral deposits in caves.Speleothems (active stalactites, wall concretions), rock walls, ceiling, and soils from the galleries of Grotta dei Cervi, Porto Badisco, Italy, were sampled to investigate the culturable heterotrophic microbial communities present in this cave. Sampling was carried out in a transect of about 230 m from the entrance to the central gallery where numerous Gram-positive bacteria were isolated from all studied sites. Members of the genera Agromyces, Arthrobacter, Rhodococcus , and particularly Streptomyces , of the order Actinomycetales, are spread throughout the whole cave. The ability of actinomycetes, and particularly of Nocardiopsis , to colonize salt-stressed environments is favored by the presence of ectoine, a compatible solute for osmotic adaptation. Selected actinomycete isolates were tested for the formation of crystals. Strains from all tested genera, except isolates of Gordonia and Nocardia , produced vaterite and/or calcite. Production of Mgcalcite was restricted to strains of Brachybacterium, Rh...

Biomediated Precipitation of Calcium Carbonate Metastable Phases in Hypogean Environments: A Short Review

Natural precipitates of metastable polymorphs of CaCO 3 , such as vaterite, are rarely found in nature however, they have been widely synthesized in laboratory under particular conditions (ie, supersaturated solutions, relative high temperatures, etc.). By SEM and XRD we recognize vaterite spherulites from culturable microbial colonies isolated from hypogean environments. Spherical bodies (∽10μin diameter), probably composed of vaterite, occur in submilimetric microbial mats and biofilms on volcanic substrates (Saint Callixtus Catacombs, Rome, Italy) and karstic caves (Altamira, Candamo, and Tito Bustillo caves, Spain, and Grotta dei Cervi, Italy) where cyanobacteria and actinomycetes are the major microbial components. These particles form beneath dense biofilms, where particular physicochemical conditions are developed by the microbial activity. Natural biofilms seems to generate microenvironments favoring the formation and preservation of metastable CaCO 3 polymorphs. This also shows a major role of microbes in processes of low-temperature alteration of different hypogean rock-substrates.

Microbial Communities Associated With Hydromagnesite and Needle-Fiber Aragonite Deposits in a Karstic Cave (Altamira, Northern Spain)

Microbial communities, where Streptomyces species predominate, were found in association with hydromagnesite, Mg5(CO3)4(OH)2.4H2O, and needle-fiber aragonite deposits in an Altamira cave. The ability to precipitate calcium carbonate in laboratory cultures suggests that these and other bacteria present in the cave may play a role in the formation of moonmilk deposits.

Isolation of five Rubrobacter strains from biodeteriorated monuments

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.

Paleolithic Art in Peril: Policy and Science Collide at Altamira Cave

Despite evidence of damaging human impacts, cave paintings may again be threatened if visitors are allowed access. In the last decade, considerable attention has been paid to the deterioration of the caves that house the worlds most prominent Paleolithic rock art. This is exemplified by the caves of Lascaux (Dordogne, France) (1) and Altamira (Cantabria, Spain), both declared World Heritage Sites. The Altamira Cave has been closed to visitors since 2002. Since 2010, reopening the Altamira Cave has been under consideration. We argue that research indicates the need to preserve the cave by keeping it closed in the near future.

Pathogenic and opportunistic microorganisms in caves

Funding from the project RNM-5137, Consejeria de Innovacion, Junta de Andalucia, is acknowledged. This is also a TCP CSD2007-00058 paper.

Microbial Communities and Associated Mineral Fabrics in Altamira Cave, Spain

Evidences of microbial colonizations were observed in Altamira Cave, Spain. These consisted of distinct small coloured colonies, both on walls and ceiling, mainly located in the area near the cave entrance, which progressed until reaching the Polychromes Hall. The colonizations were characterized by a high morphological and microstructural variability and related to biomineralization processes. Two main types of CaCO3 deposits were related to the colonies: rosetteor nest-like aggregates of rhombohedral calcite crystals, and spheroid to hemispheroid CaCO3 elements. Colonies distribution seems to be controlled by microenvironmental conditions inside the cavity. The areas of the cave showing higher temperature, relative humidity, and CO2 biomineralization capability.

The biogeochemical role of Actinobacteria in Altamira Cave, Spain

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.