- Количество слайдов: 11
March 10, 2009 Australian wrestles kangaroo from family home 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. • Exam I due Thursday, March 12 (11 am) • Proposal descriptions due Thursday, March 26
Fe Isotope Fractionation From: Beard et al. , 1999, Science 285: 1889 -1892
Fe Isotopes • Modern Fe cycle 8 No distinction for Fe. OB 8 Distinct for DIRB 8 Distinct for Fe. S (SRB) • Early Earth Fe cycle 8 Some kind of oxidant present 8 Fe respiration 2. 7 -2. 9 Ga Johnson and Beard, 2006. GSA Today, Vol. 16(11), pp. 4 -10.
Biomineralization: Forming Biogenic Minerals BIM BCM biologically induced mineralization (Fe bacteria, Sulfate reducers) biologically controlled mineralization (Magnetotactic bacteria, Shewanella) • 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 Types of oxides: Magnetite (Fe 3 O 4), Greigite (Fe 3 S 4), Pyrrhotite (Fe 7 S 8)
BCM: Shewanella • Ferrihydrite inclusions Glasauer, et al. 2002. Science Vol. 295: 117.
Magnetic Bacteria • Characteristics 8 Bacteria only 8 Motile, Microaerophiles 8 Magnetosomes Magnetospirillum gryphiswaldense http: //www. mpi-bremen. de/magneto/research/ http: //www. energy. soton. ac. uk/research/bio_magneto_bac. html http: //geography. lancs. ac. uk/cemp/atlas/biogenic_1. htm
http: //www. calpoly. edu/~rfrankel/
http: //www. calpoly. edu/~rfrankel/ http: //www. mpi-bremen. de/magneto/research/
Function of Magnetic Particles? Magnetotaxis allows passive orientation Aerotaxis drives localization http: //www. calpoly. edu/~rfrankel/ MOVIE link: http: //www. biophysics. uwa. edu. au/STAWA/magbac_5. html
Biochemistry of Magnetosome Formation 1. Fe+3 reduction and uptake by siderophores 2. Fe+2 uptake within magnetosome membrane 3. Oxidation of Fe+2 to Fe+3 http: //www. mpi-bremen. de/magneto/research/
Magnetic Minerals as Biomarkers • Consistent size indicates biogenic magnetite 8 Need better techniques to distinguish particles FOSSILIZED MAGNETOTACTIC BACTERIUM IN THE ORGUEIL METEORITE Tan and Van Landingham (1966) Image of freshly fractured surface of a chip from ALH 84001 meteorite Image - NASA AMES http: //www. astrobio. net/news/print. php? sid=250 http: //www. abc. net. au/science/news/space/Space. Republish_252236. htm