Transcript What is Geomicrobiology?

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 (11am)
• Proposal descriptions due Thursday, March 26
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
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 (Fe3O4), Greigite (Fe3S4),
Pyrrhotite (Fe7S8)
BCM: Shewanella
• Ferrihydrite inclusions
Glasauer, et al. 2002. Science Vol. 295:117.
Magnetic Bacteria
• Characteristics
Bacteria only
Motile, Microaerophiles
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/biogen/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
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 ALH84001
meteorite
Image - NASA AMES
http://www.astrobio.net/news/print.php?sid=250
http://www.abc.net.au/science/news/space/SpaceRepublish_252236.htm