Lab Opportunities
All semesters
Sophomore
No experience necessary
General Biology
Project Work
10-15 hours, or students preference
A one-semester commitment would be required
We study signal transductions in the protozoan Paramecium, using
biochemical, genetic, molecular genetic, cell biological, and
electrophysical tools. Paramecium propels itself through the
surrounding medium by the coordinated beating of the cilia that cover
its surface. In response to chemical, mechanical, and thermal stimuli
the cell changes direction or speed by changing the orientation or
frequency of its ciliary beat. Stimuli initially register as a change
in membrane potential, and then Ca2+, cyclic AMP, and cyclic GMP serve
as second messengers that regulate the ciliary beat.
One of the extracellular compounds to which Paramecium responds to is
GTP, apparently through a plasma membrane receptor that may be related
to the purinoceptors found in many animal cells that respond to
extracellular ATP. Extracellular GTP elicits slow oscillations in the
membrane potential of Paramecium, which correspond to alternating
periods of forward and backward swimming. Mutants specifically
defective in their behavioral response to GTP also lack this membrane
response to GTP. The mechanism by which the extracellular signal (GTP)
is transduced into a change in swimming behavior is central interests
of the laboratory.
An undergraduate student beginning in my lab might, for example,
explore the role of an enzyme (adenylyl cyclase or phospholipase C
(PLC) in the signal transduction. He or she would determine whether a
compound that inhibits tone of these enzymes changes the cellular
response to GTP. If so, then that enzyme is implicated in the signal
transduction mechanism. The student would use a simple behavioral assay
for the response (observation of the swimming behavior of individual
cells in the dissecting microscope) asking whether the drug alters the
swimming response to GTP.