HR: 0830h
AN: B51C-0970    [PDF]
TI: The Biosignatures of Controlled Bbiomineralization of Pyrite From Fe$^{2+}$ and H$_{2}$S by Thiomonas sp.
AU: Popa, R
EM: rpopa@usc.edu
AF: University of Southern California, 3651 Trousdale Parkway SCI 223, Los Angeles, CA 90089-0740 United States
AU: Souza-Egipsy, V
EM: souzaegi@usc.edu
AF: University of Southern California, 3651 Trousdale Parkway SCI 223, Los Angeles, CA 90089-0740 United States
AU: Mielke, R
EM: Randall.E.Mielke@jpl.nasa.gov
AF: Jet Propulsion Laboratory, 4800 Oak Grove Dr. Mail Stop 183-301, Pasadena, CA 91801 United States
AU: * Nealson, K H
EM: knealson@usc.edu
AF: University of Southern California, 3651 Trousdale Parkway SCI 223, Los Angeles, CA 90089-0740 United States
AB: A novel strain of Thiomonas called strain 51 was recently isolated from a subsurface sulphide-rich aquifer. Under defined culture conditions this strain is capable of forming a variety of minerals such as elemental sulfur, mackinawite, troilite, cubic FeS greigite and pyrite. Previous studies suggested that the formation of these minerals is a case of biologically controlled biomineralization. Strain 51 is uniquely capable of using the formation of iron sulphides, including pyrite, from ferrous iron (Fe$^{2+}$) and hydrogen sulphide (H$_{2}$S) as a source of energy. This type of biomineralization is used in a variety of models of early life and is relevant for life on Earth. Neither the mechanism used by strain 51 to produce iron sulphides, nor the resulting biosignatures have yet been elucidated. We performed a microanalytical study by using transmission electron microscopy (TEM) with energy dispersive X-ray spectroscopy (EDS) to study the ultrastructural distribution of these deposits in relation to the cells as a means of obtaining insights into the mechanism of this type of biomineralization. The formation of iron sulfides by strain 51 appears to be a stepwise process. Prior to forming pyrite, cells produce elemental sulphur (S$^{o}$) and an Fe-rich precipitate outside the cells, and accumulate considerable amounts of iron in the periplasmic space and in the cytoplasm close to the membrane, in complexes with phosphate, silicate and sulphide. During subsequent steps iron monosulphide minerals are formed such as cubic FeS, mackinawite, and greigite. Pyritization is a late step and appears as nanometer-sized microcrystallites in the periplasmic space and submicron sized microcrystallites outside the cells. The arrangements of these crystals may be important biosignatures in micropaleontology.
DE: 0400 Biogeosciences
DE: 4805 Biogeochemical cycles (1615)
DE: 4832 Hydrothermal systems
DE: 4840 Microbiology
DE: 6225 Mars
SC: Biogeosciences [B]
MN: 2003 Fall Meeting