title: The biogeochemical role of  Actinobacteria in Altamira Cave, Spain.
abstract: 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.
authors.affiliation: Laboratorio de Petrologia Aplicada, Departamento de Ciencias de la Tierra y del Medio Ambiente, Universidad de Alicante, Alicante, Spain.
authors.forename: Soledad
authors.initials: S
authors.lastname: Cuezva
authors.forename: Angel
authors.initials: A
authors.lastname: Fernandez-Cortes
authors.forename: Estefania
authors.initials: E
authors.lastname: Porca
authors.forename: Lejla
authors.initials: L
authors.lastname: Pašić
authors.forename: Valme
authors.initials: V
authors.lastname: Jurado
authors.forename: Mariona
authors.initials: M
authors.lastname: Hernandez-Marine
authors.forename: Penelope
authors.initials: P
authors.lastname: Serrano-Ortiz
authors.forename: Bernardo
authors.initials: B
authors.lastname: Hermosin
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Cañaveras
authors.forename: Sergio
authors.initials: S
authors.lastname: Sanchez-Moral
authors.forename: Cesareo
authors.initials: C
authors.lastname: Saiz-Jimenez
mesh_terms: D039903:Actinobacteria / Q000145:classification / Q000302:isolation & purification* / Q000378:metabolism*; D002119:Calcium Carbonate / Q000378:metabolism; D002245:Carbon Dioxide / Q000378:metabolism; D059552:Caves / Q000737:chemistry / Q000382:microbiology*; D013030:Spain
chemical_list: D002245:Carbon Dioxide; D002119:Calcium Carbonate