Abstract
The response of cells to changes in their physico-chemical
micro-environment is essential to their survival. For example, bacterial
magnetotaxis uses the Earth's magnetic field together with chemical
sensing to help microorganisms move towards favoured habitats. The
studies of such complex responses are lacking a method that permits the
simultaneous mapping of the chemical environment and the response of the
organisms, and the ability to generate a controlled physiological
magnetic field. We have thus developed a multi-modal microscopy platform
that fulfils these requirements. Using simultaneous fluorescence and
high-speed imaging in conjunction with diffusion and aerotactic models,
we characterized the magneto-aerotaxis of Magnetospirillum gryph is
waldense. We assessed the influence of the magnetic field (orientation;
strength) on the formation and the dynamic of a micro-aerotactic band
(size, dynamic, position). As previously described by models of
magnetotaxis, the application of a magnetic field pointing towards the
anoxic zone of an oxygen gradient results in an enhanced aerotaxis even
down to Earth's magnetic field strength. We found that neither a
ten-fold increase of the field strength nor a tilt of 45 degrees
resulted in a significant change of the aerotactic efficiency. However,
when the field strength is zeroed or when the field angle is tilted to
90 degrees, the magneto-aerotaxis efficiency is drastically reduced. The
classical model of magneto-aerotaxis assumes a response proportional to
the cosine of the angle difference between the directions of the oxygen
gradient and that of the magnetic field. Our experimental evidence
however shows that this behaviour is more complex than assumed in this
model, thus opening up new avenues for research.
Users
Please
log in to take part in the discussion (add own reviews or comments).