..fungal titers?

Austin Reade rbsjunk at hfx.andara.com
Thu Feb 22 14:58:12 EST 2001


<nmaccallister at webtv.net> wrote in message
news:7036-3A94CB9D-109 at storefull-111.iap.bryant.webtv.net...
>  I still love that story
> identifying the first production centrifuges as recycled washing
> machines...(Isn't that great!)

Must have missed that post.  I have used washing machines as (almost)
disposable, low-tech fermentors.
>

> 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?

All of the above, molds have complex life-cycles.  Sexually produced
ascospores, asexually produced conidia and mycelial fragments can all act as
inocula to start new colonies.

>
> Will the broth-bred mycelium produce either conidia or ascus spores in
> the absence of an environmental or nutritional stress?,

In my experience agitated (stirred) liquid cultures of microfungi (eg
Aspergillus, Penicillium, Fusarium, Trichoderma) do not produce conidia.
The case I outlined in my email to you was unusual.

Static liquid cultures will yield conidia which are produced on the mycelium
growing at the surface of the liquid in the  same way as a solid surface
culture.

>.. 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?.

Out of my depth here, those mycology lectures were such a long time ago but
for what it's worth.....   Aspergilli and pencillia may reproduce asexally
(anamorphs) or sexually (teleomorphs).  Some species are only known by their
anamorph, the teleopmorph has not yet been seen.  Other species where the
teleomorph has been observed may be encountered in either state.  The
anamorph only produces conidia whereas the teleomorph produces  both conida
and ascospores.  I think you can get ascospore production in a pure culture
of a teleomorph.  [I had speculated further here on how this may occur but I
am not prepared to risk the wrath of any real mycologists!!  You should
perhaps pose this question on  bionet.mycology]

.> 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.

This is obviously a laboratory excercise but it does work.  Whether the open
ends of mycelial fragments reseal themselves I don't know but I do recall
that the literature at the time suggested one should limit blending so that
you were left with fragments where there were at least two septa bounding
some cytoplasm within a section of mycelium.  The inference was that if you
blended any further all the cell contents would leak out!  Begs the question
whether this method would work on Zygomycetes (no septa).

For your purposes conidia will be the most convenient source of inoculum.


Austin Reade
Reade BioSciences Inc
Halifax,NS, Canada







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