infection of fungi by protozoa

Peter Herman x5495 rpeter at
Tue Feb 7 13:44:34 EST 1995

In article <Louis.bernier-060295154722 at> Louis.bernier at (Louis Bernier) writes:
>I was recently contacted by a graduate student in soil microbiology. She is
>working on Penicillium spp. she has isolated from the soil and she has
>that all her cultures are contaminated with protozoa (probably amebas, she 
>believes). She is looking for information on how to get rid of these little
>beasts (the protozoa of course, not the fungi !). If any of you has some 
>helpful hints, please contact me and I will pass the information on to the 

	There are 2 good ways

1)	Get the cultures sporulating.  Suspend many spores in a
surfactant (like 0.05% Tween 20).  Do serial dilutions of the
spores.  Put a drop on drop of suspension on the plate and spread or
run it around to single spore.  Some of the colonies will be amoeba

2)	Make a metal or glass ring with feet (I use 0.5 cm slices of
20 mm pyrex test tubes with 3 mm glass beads welded on to the ring in
3 spots).  Put sterile ring in sterile petri dish.  Pour in agar so
that the agar level is over the feet and about mid-ring.  Inoculate
contaminated culture in the ring when the agar is completely set and
plates are dried. (you have to watch out for condensate).  The
fungus will grow down through the agar and out from under the ring.
cut a bit of the growing front when it is 2-3 cm beyond the ring.
You may need to repeat the process.  Bacteria and protozoa stay
inside the ring because they cannot penetrate the agar.

I use this to clean up field isolates of watermolds all the time and
it works like a charm.  Thank yous to John R. Raper who thought of
this technique eons ago!

Hope this helps

*   Peter Herman, Dept. of Biology	Phone: +1 505 646 4532    *
*   New Mexico State University		Fax:   +1 505 646 5665    *
*   Box 30001, Dept. 3AF					  *
*   Las Cruces, NM 88003 USA		e-mail rpeter at    *

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