HR: 1340h
AN: B13A-1034    [Abstracts]
TI: Biomineralization of Acidophilic Eukaryotes in Iron-rich Environments: Implications in Microbial Fossil Formation
AU: * Souza-Egipsy, V
EM: souzaev@inta.es
AF: Centro de Astrobiologia CSIC-INTA, Crt. Torrejon a Ajalvir Km 4, Torrejon de Ardoz, Mad 28850 Spain
AU: Aguilera, A
EM: aaguilera@cbm.uam.es
AF: Centro de Astrobiologia CSIC-INTA, Crt. Torrejon a Ajalvir Km 4, Torrejon de Ardoz, Mad 28850 Spain
AB: This study focus on the influence of eukaryotic microorganisms on the formation of iron-rich deposits in an extreme acidic environment, Rio Tinto, Spain. The cell walls of microscopic algae (Cyanidium, Chlorella, Mesotaenium, Nitzschia) and some protist as Euglena mutabilis have been described as sites of nucleation of iron-rich minerals. Combined scanning and transmission electron microscopy (TEM, SEM) with non-destructive microanalytical techniques (EDS) have been used in order to determine the microorganisms ultrastructure preservation related to biominealization mechanisms, and the nature of the minerals in the sediments. The presence of microorganisms forming biofilms on the riverbed influence the precipitation of minerals and the final texture of the layered sediments. In some cases, silica permineralization of the cell walls leads to the formation of cell-shaped structures that may be considered as biomarkers. In other cases, the epicellular deposition of minerals preserved the texture of the biofilm in the sediments. In the case of soft cell wall microorganisms as Euglena mutabilis the biomineralization mechanisms include the intracellular sequestration of Fe, leading to the preservation of cytoplasmic structures. The process of biomineralization in eukaryotic microorganisms has permited the preservation of microfossils in a very oxidizing environment where organic compounds are unlikely to be preserved within sediments. Studies of mechanisms of microbial fossil formation in modern extreme environments that support microbial comunities are necessary to develop criteria for identifying inorganic traces of microbial life.
DE: 0419 Biomineralization
DE: 0424 Biosignatures and proxies
DE: 0448 Geomicrobiology
DE: 0456 Life in extreme environments
DE: 0463 Microbe/mineral interactions
SC: Biogeosciences [B]
MN: Fall Meeting 2005