Centrifuging MO's

Alec Chambers jac55 at cas.org
Mon Apr 15 11:02:21 EST 1996

Andrea Marie Habura wrote:
> Hi, Scott!
> The optimal g will depend on what you're trying to remove from your
> bacterial culture. I'm a cellular slime mold person, and we use
> an 800 x g spin (about 10 minutes) to pellet slime mold myxamoebae
> while leaving the bacteria they eat (E. coli, in our case) in the
> supernatant. If your contaminant is about the size of a yeast cell,
> this should work well. If it's smaller, a faster spin may be in order.

	Another possibility is a density fractionation, if 
	you can find buoyant densities for your microorganisms.

	You would overlay the sample on a layer of a dense medium,
	a Ficoll solution springs to mind for no good reason, and
	give the sample a good had spin to force the denser
	cells through the cushion.  If you get the density of the 			cushion
right, then the two should separate quite cleanly.
	for something as massive as microbial cells you shouldn't
	need to worry about a thin sample layer.  You might also
	be able to use Percoll, but the pelleted cells would be
	mixed up in the pelleted silica and would probably need to
	be discarded.

	Another possibility is fractionation through an
	elutriator or zonal rotor (depending upon how big
	your sample is).


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