march 10, 2009 exam i due thursday, march 12 (11am) proposal descriptions due thursday, march 26...
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March 10, 2009
• Exam I due Thursday, March 12 (11am)• Proposal descriptions due Thursday, March 26
CANBERRA, Australia - When a dark intruder smashed through his bedroom window and repeatedly bounced on his bed, Beat Ettlin was initially relieved to discover it was a kangaroo.The kangaroo, which Ettlin said was around his height, 5 foot 9 inches (176 centimetres), left a trail of blood through the house and claw gouges in the wooden frame of his bed.Ettlin, who was left wearing just his shredded underpants and with scratch marks on his leg and buttocks, described himself as "lucky." Kangaroos rarely harm humans, but when they do, it is usually because they feel cornered. They have been known to disembowel people with the claws of their powerful hind legs.
Australian wrestles kangaroo from family home
Fe Isotope Fractionation
From: Beard et al., 1999, Science 285:1889-1892
Fe Isotopes• Modern Fe cycle
No distinction for FeOB Distinct for DIRB Distinct for FeS (SRB)
• Early Earth Fe cycle Some kind of oxidant present Fe respiration 2.7-2.9 Ga
Johnson and Beard, 2006. GSA Today, Vol. 16(11), pp. 4-10.
Biomineralization:Forming Biogenic Minerals
BIM biologically induced
mineralization(Fe bacteria, Sulfate reducers)
BCMbiologically controlled
mineralization(Magnetotactic bacteria, Shewanella)
Types of oxides:
Magnetite (Fe3O4), Greigite (Fe3S4),
Pyrrhotite (Fe7S8)
• Result of metabolic activity
• Extracellular particles
• Poorly crystallized minerals
• Broad size distribution
• Direct synthesis of mineral
• Typically within cell
• Well-ordered crystals
• Narrow size distributions
BCM: Shewanella
• Ferrihydrite inclusions
Glasauer, et al. 2002. Science Vol. 295:117.
Magnetospirillum gryphiswaldense
http://www.mpi-bremen.de/magneto/research/http://www.energy.soton.ac.uk/research/bio_magneto_bac.htmlhttp://geography.lancs.ac.uk/cemp/atlas/biogen/biogenic_1.htm
Magnetic Bacteria
• CharacteristicsBacteria onlyMotile, MicroaerophilesMagnetosomes
http://www.calpoly.edu/~rfrankel/
http://www.calpoly.edu/~rfrankel/http://www.mpi-bremen.de/magneto/research/
http://www.calpoly.edu/~rfrankel/MOVIE link: http://www.biophysics.uwa.edu.au/STAWA/magbac_5.html
Magnetotaxis allows passive orientation
Aerotaxis drives localization
Function of Magnetic Particles?
http://www.mpi-bremen.de/magneto/research/
Biochemistry of Magnetosome Formation
1. Fe+3 reduction and uptake by siderophores2. Fe+2 uptake within magnetosome membrane3. Oxidation of Fe+2 to Fe+3
Image - NASA AMES
FOSSILIZED MAGNETOTACTIC BACTERIUM IN THE ORGUEIL METEORITETan and Van Landingham (1966)
Image of freshly fractured surface of a chip from ALH84001
meteoritehttp://www.astrobio.net/news/print.php?sid=250
http://www.abc.net.au/science/news/space/SpaceRepublish_252236.htm
Magnetic Minerals as Biomarkers
• Consistent size indicates biogenic magnetiteNeed better techniques to distinguish particles