Date: Sat, 12 Oct 1996 10:14:17 -0500
From: r-halgren@nwu.edu (Robert G. Halgren)
Subject: [10676] Re: [10645] Contaminated flask.

>Date: Thu, 10 Oct 1996 21:51:41 -0700
>From: fredrick@well.com (Fred Paget)

Always happens with the best stuff, right?  Never that 100th
flask of a pink phal...  I usually throw contaminated flasks away, but
I have had some luck saving them. My latest experiment in flask rescue
involved a Paph hybrid with a big spot of mold in the middle of the
flask.  I removed the protocorms to 3%H202 (drug store brand, straight
out of the bottle) and allowed them to soak for about 5 minutes.  I
then plated to three replate flasks.  One of these flasks was with the
addition of 1mg/ml Amphotericin B (Fungizone), the second 2.5mg/ml AB,
and the third was a "normal" replate flask.  I replated out of the
hydrogen peroxide, without any attempt to wash.  I did the above
flasks in the order indicated, so the last flask's protocorms had been
in H2O2 longer than the first.  For the last flask, I just dumped the
entire remainder of protocorms in H2O2 into the flask, and aspirated
off some of the extra.  So far (1 month out), there is no evidence of
contamination in any of those three flasks.  Since I don't know what
AB does to Paphs, I would recommend the last approach.  Looking at
about 15 minutes of a 3% H2O2 soak and a fair amount of residual H2O2
in the flask.  Did I get every last nasty?  Every last actively
growing one, anyway, spores might take longer to show up.  Did I kill
the plants?  Not as far as I can tell, they are still green.  I may
have set them back a bit.

Rob