HR: 0800h
AN: B31C-0999    [Abstracts]
TI: Magentic Properties of Magnetites Produced by Magnetotactic Bacteria
AU: * Pan, Y
EM: yxpan@mail.iggcas.ac.cn
AF: Institute of Geology and Geophysics, Chinese Academy of Sciences, 19 Beituchengxi Road, Beijing, 100029 China
AU: Lin, W
EM: weilin@mail.iggcas.ac.cn
AF: Institute of Geology and Geophysics, Chinese Academy of Sciences, 19 Beituchengxi Road, Beijing, 100029 China
AU: Zhu, R
EM: rxzhu@mail.iggcas.ac.cn
AF: Institute of Geology and Geophysics, Chinese Academy of Sciences, 19 Beituchengxi Road, Beijing, 100029 China
AU: Yu, S
EM: yusheng@rose.nsfc.gov.cn
AF: Institute of Geology and Geophysics, Chinese Academy of Sciences, 19 Beituchengxi Road, Beijing, 100029 China
AU: Davila, A F
EM: fon@geophysik.uni-muenchen.de
AF: Department of Earth and Environmental Sciences, Ludwig-Maximilians-University, Theresienstr. 41/IV, Munich, D-80333 Germany
AU: Winklhofer, M
EM: michael@geophysik.uni-muenchen.de
AF: Department of Earth and Environmental Sciences, Ludwig-Maximilians-University, Theresienstr. 41/IV, Munich, D-80333 Germany
AU: Petersen, N
EM: petersen@geophysik.uni-muenchen.de
AF: Department of Earth and Environmental Sciences, Ludwig-Maximilians-University, Theresienstr. 41/IV, Munich, D-80333 Germany
AB: Magnetotactic bacteria (MTBs) are a diverse group of motile, aquatic bacteria including coccoid, rodshaped, vibrioid, spirilla and multicellular forms that orient and migrate along the geomagnetic field. Their intracellular magnetites (magnetosomes) are characterized by narrow grain-size distributions (30 to 120 nm), distinct species-specific crystal morphology, chemical purity, and arrangement in single or multiple linear chains. The magnetic properties of magnetosome are of great interest for sedimentary magnetism, fine-grain magnetism, magnetic materials, biomineralization in organisms and biomarkers in rocks. We will report magnetic measurements on both air-dried cells containing solely MTBs (wild-type cocci and Magnetobacterium bavaricum), which were directly isolated from the Chiemsee lake sediments, and the whole fresh cells as well as isolated magnetosomes of laboratory cultured strain, Magnetospirillum gryphiswaldense MSR-1. Results show that: (1) the magnetosomes in cells are dominated by single-domain (SD) magnetite; (2) Low-temperature cycling of saturation isothermal remanent magnetization (SIRM) and first-order-reversal-curve (FORC) diagrams of the samples differ significantly from the ones measured on SD-magnetite powder samples; and (3) the Verwey transition temperature (Tv, 100 K) of bacterial magnetites is distinctly lower than that from stoichiometric magnetite (Tv, 120 to 125 K). Moreover, the effects of related low-temperature oxidation and chain arrangement in measured samples will be discussed.
DE: 0419 Biomineralization
DE: 0424 Biosignatures and proxies
DE: 1505 Biogenic magnetic minerals
DE: 1540 Rock and mineral magnetism
SC: Biogeosciences [B]
MN: Fall Meeting 2005