..fungal titers?

nmaccallister at webtv.net nmaccallister at webtv.net
Thu Feb 22 03:19:41 EST 2001


Well thanks again for your kind comments and interesting points of view.
I appreciate hearing these informations from you.  I like the usages of
"Waring blenders" and "scotch tape preps".  I admire the kind of
practical ingenuity these ideas represent.  I still love that story
identifying the first production centrifuges as recycled washing
machines...(Isn't that great!)

Anyway,.. no, I'm not working foods or drugs,.. just mainly doing raw
material screenings in a warehouse.  The samples comprise a lot of
botanicals (ginger, ginseng, dandelion)..but these are not final
products. I just don't want to keep a contaminated warehouse!

I do get asked to check the effectiveness of an occasional preservative
by a friend down the hall.  This will usually be a wax or paste carrying
a particular concentration of a preservative.  To satisfy that request,
I will have to inoculate the wax with a known titer of challenge
organism(s),.. and then compare the T(zero) microbial count to a
microbial count performed 7 days later T(seven).  An effective
preservative will reduce the number of viable microbes by a thousandfold
(bacteria), or a hundredfold (fungi).  That reduction I called a "kill
rate", and I believe that with some "preservatives" (like Benzyl
alcohol) that is exactly what occurs.

I did check my old copy of Stanier's 'The Microbial World' and noticed
there is some complexity regarding the nature of the "growing point"
responsible for the colony formation on the agars.  Were they spores,
from an ascus,.. or were they conidia, from hyphae tips,.. or is it
possible that mycelial fragments can  themselves produce a growth on the
agar?

Will the broth-bred mycelium produce either conidia or ascus spores in
the absence of an environmental or nutritional stress?,.. Will A. niger
produce an ascus (which I believe entails a diploid phase) all by
itself, or does it require a second colony with which to mate?.. And can
mycelial fragments really seal themselves back up and resume growth
after the vortexing?.. Perhaps this is a low incidence kind of thing,
and a minor source of growing points compared to conidia and asci
spores.

Meanwhile, I think I will follow the general approach of streaking out
the starter on solid media, waiting for good growth and color, and then
wash/dislodge with a broth to collect the spores.  All recommendations
suggest I will then have to dilute the wash DOWN to get to 10^6 titre.
I'll just wait and see!

Judy, is the "scotch tape prep" a method of collecting spores for
transfer?.. or freezing?  
Or do you let the spores germinate on the tape in order to view the
mycelium? ..(Maybe all 3?)

Austin, I've already got a book ordered on preservatives and testing
(Kabara),.. and I will look for one on mycology as well.  The
fermentation processes you've worked in sound interesting, and I'll bet
there is a lot going on there!
   
Well, thanks again,..and "Happy Birthday, Judy!!!"

Thanks to each of you!  NM






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