GEOC 135 |
| Dirk Schüler, Max Planck Institute f. Marine Microbiology, Celsiusstr. 1, Bremen, 28359, Germany |
| Magnetotactic bacteria (MTB) are able to orient along magnetic fields based on specific intracellular structures, the magnetosomes, which are nanometer-sized particles of magnetite (Fe3O4). Magnetosome biomineralization is an example for controlled mineral formation in aquatic sediments and has been recently considered for use as biosignature to identify presumptive Martian magnetofossils. However, the biogeochemical interactions of MTB as well as their intracellular biomineralization have been poorly chacterized. We studied the diversity and occurrence of MTB in aquatic sediments and found their vertical distribution correlated with physico-chemical gradients including oxygen and iron. Pure cultures of the model organism Magnetospirillum gryphiswaldense are capable of magnetite synthesis from extracellular ferrous iron, which involves partial intracellular oxidation of iron. Magnetite biomineralization occurs within a subcellular compartment provided by the magnetosome membrane (MM), which controls the magnetite precipitation by biological means. We identified a number of specific MM-proteins, which have functions in the compartmentalization of biomineralization, transport of iron and the control of nucleation and crystal growth. |
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Microbially Mediated Manganese and Iron Oxidation in the Biosphere
8:00 AM-12:15 PM, Wednesday, March 31, 2004 Marriott -- Marquis NE, Oral
Division of Geochemistry |