Bacteria use a compass to
navigate
Presented by:
Marwa Mahmoud
W hat does Christopher Columbus have
in common with tiny microorganisms?
Scientists have known for a long time that
bacteria can orient themselves using:
 Light
 Temperature
 Food
And alarm substances or other chemical compounds
 Richard P. Blakemore in 1975, discovered the
existence of magnetotactic bacteria in a mud
sample.
 These bacteria have organelles called
magnetosomes that contain magnetic crystals.
LIFE FORMS SHAPED
LIKE TINY FOOTBALLS
 Freshwater and marine habitats.
 Anaerobes -too much oxygen can kill them.
 Mud-water interface.
 One micrometer (a thousandth of a
millimeter) in size.
 Spiral, rod or comma shaped
life forms; some even resemble
tiny footballs.
What is the structure of these extremely
unusual nano crystals?
Figure 1: Diagram of a magnetotactic bacterium
The magnetosomes present in various types
of bacteria often have different shapes:
Figure 2 : The electron microscopial images show structures in the shape
of droplets (a), projectiles (b) and cubes (c, d). The magnetic particles are
arranged in either one (a, b) or several (c, d) chains.
Figure 3: Diagram showing how magnetotactic bacteria use magnetotaxis to
swim to the OATZ in the Northern versus the Southern Hemisphere on Earth
30 s
120 s
Figure 4: The microorganisms that are initially distributed uniformly and
randomly, swim in a controlled manner to the northerly edge of the
sample when a magnetic field is applied.
 Biotechnological application for medical diagnostics
Magnetosome particles could be used
in the detection of tumours (magnetic
resonance tomography).
 Help us to understand the origin of life
on Earth and elsewhere in the universe.
 We still have not managed to grow bacteria in
the laboratory in the required quantities.
 The production of magnetite is particularly
sensitive to subtle changes in the cultivation
process.
 And the greater the quantity,
the more complex the procedure.
"Now, my own suspicion is that the
universe is not only queerer than we
suppose, but queerer than we can
suppose. I suspect that there are more
things in heaven and earth than are
dreamed of, or can be dreamed of, in
any philosophy.” J.B.S. Haldane
References:
1. Faivre, D. & Schüler D. Magnetotactic bacteria and magnetosomes.
Chemistry Reviews 108, 4875–4898 (2008).
2. Gorby, Y. A., Beveridge T. J., & Blakemore R. P. Characterization
of the bacterial magnetosome membrane. Journal of Bacteriology
170, 834–841 (1988).
3. Thomas-Keprta K. L. et al. Magnetofossils from ancient mars: a
robust biosignature in the martian meteorite ALH84001. Applied and
Environmental Microbiology 68, 3663–3672 (2002).