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