Microbial mediation of complex subterranean mineral structures.
Helictites--an enigmatic type of mineral structure occurring in some caves--differ from classical speleothems as they develop with orientations that defy gravity. While theories for helictite formation have been forwarded, their genesis remains equivocal. Here, we show that a remarkable suite of helictites occurring in Asperge Cave (France) are formed by biologically-mediated processes, rather than abiotic processes as had hitherto been proposed. Morphological and petro-physical properties are inconsistent with mineral precipitation under purely physico-chemical control. Instead, microanalysis and molecular-biological investigation reveals the presence of a prokaryotic biofilm intimately associated with the mineral structures. We propose that microbially-influenced mineralization proceeds within a gliding biofilm which serves as a nucleation site for CaCO3, and where chemotaxis influences the trajectory of mineral growth, determining the macroscopic morphology of the speleothems. The influence of biofilms may explain the occurrence of similar speleothems in other caves worldwide, and sheds light on novel biomineralization processes.
University of Toronto, 35 St. George street, M5S 1A4 Toronto, (CA).
Nicola
N
Tisato
ETH Zurich, Institute of Integrative Biology, 8092 Zurich, (CH), now at: Syngenta Crop Protection, Münchwilen AG, Werk Stein, Schaffhauserstrasse, 4332 Stein AG, (CH).
Stefano F F
SF
Torriani
Université Montpellier 2, Master EcoSystèmeS, Place Eugène Bataillon, 34095 Montpellier cedex5, (FR), now at Umeå Universitet, Climate Impacts Research Centre, 98 107 Abisko (SWE).
Sylvain
S
Monteux
Bologna University, Department of Biological, Geological and Environmental Sciences, Italian Institute of Speleology, Via Zamboni 67, 40126 Bologna (IT).
Francesco
F
Sauro
Bologna University, Department of Biological, Geological and Environmental Sciences, Italian Institute of Speleology, Via Zamboni 67, 40126 Bologna (IT).
Jo
J
De Waele
ETH Zurich, ERDW, Sonneggstrasse 5, 8092 Zurich (CH).
Maria Luisa
ML
Tavagna
Bologna University, Department of Biological, Geological and Environmental Sciences, Italian Institute of Speleology, Via Zamboni 67, 40126 Bologna (IT).
Ilenia M
IM
D'Angeli
FFS -Fédération Française de Spéléologie, 28 rue Delandine, 69002 LYON, (FR).
Daniel
D
Chailloux
FFS -Fédération Française de Spéléologie, 28 rue Delandine, 69002 LYON, (FR).
Michel
M
Renda
ETH Zurich, ERDW, Sonneggstrasse 5, 8092 Zurich (CH).
Timothy I
TI
Eglinton
ETH Zurich, ERDW, Sonneggstrasse 5, 8092 Zurich (CH).
Tomaso R R
TR
Bontognali
D018441:Biofilms / Q000254:growth & development*; D002119:Calcium Carbonate / Q000737:chemistry / Q000378:metabolism*; D059552:Caves / Q000382:microbiology*
D002119:Calcium Carbonate