"Microorganisms Use Helical Motion to Orient to External Signals"
The orientation of microorganisms to external stimuli
(light, temperature
gradients, chemical concentration gradients) has been
studied for over 100
years. Two general forms of orientation have been
recognized: (1) kinesis,
in which the organism performs a "biased random walk"
to migrate in the
direction of the stimulus, and (2) taxis, in which an
organisms identifies
the direction of the stimulus and turns in that direction.
Kineses in
single-celled microorganisms have been widely studied,
including the
molecular bases of signal transduction and locomotor
response. Taxes have
also been identified in microorganisms, but they are
more poorly understood.
Almost all microorganisms move along helical trajectories.
I will explain
how helical motion permits a microorganism to determine
the direction of a
stimulus and how this can be coupled to simple locomotor
responses that
enable taxis.