>We have some problems with axenic cultures in our lab. Until now we have
>always used ampicillin (50 microg/ml final concentration) as antibioticum,
>but some "bacteria" (?) seem to be resistent. Has anyone already used other
>antibiotica?
>
We sometimes use ampicillin also, especially in plates to be spread after
biolistic transformation experiments where the risk of contamination is
pretty high. However I find in general that brute force is a better
cleanup technique. Streak cultures at low density on highly nutritive
medium (e.g. containing yeast extract), where any contamination will be
readily apparent. Using a fine glass needle under a dissecting scope,
manipulate individual Chlamy cells away from the mass of contaminated
culture. Inspect the plates daily under the microscope, and continue to
move the algal cells away from the bacteria (or fungi). When you find a
clean, uncontaminated colony, transfer it with a sterile toothpick to a
fresh plate.
The Chlamydomonas Sourcebook has some additional suggestions for
contamination control on pages 48-50.
Elizabeth Harris
chlamy at acpub.duke.edu
