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.

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Two novel species of the fungal genus Ochroconis, O. lascauxensis and O. anomala have been isolated from the walls of the Lascaux Cave, France. The interest in these fungi and their melanins lies in the formation of black stains on the walls and rock art which threatens the integrity of the paintings. Here we report solid-state cross polarization magic-angle spinning 13C and 15N nuclear magnetic resonance (NMR) spectroscopy and surface-enhanced Raman spectroscopy (SERS) of the melanins extracted from the mycelia of O. lascauxensis and O. anomala in order to known their chemical structure. The melanins from these two species were compared with those from other fungi. The melanins from the Ochroconis species have similar SERS and 13C and 15N NMR spectra. Their chemical structures as suggested by the data are not related to 3,4-dihydroxyphenylalanine, 5,6-dihydroxyindole or 1,8-dihydroxynaphthalene precursors and likely the building blocks from the melanins have to be based on other phenols that react with the N-terminal amino acid of proteins. The analytical pyrolysis of the acid hydrolysed melanin from O. lascauxensis supports this assumption.