Mould-yeast dimorphism

Peter Herman rpeter at nmsu.edu
Tue Aug 18 16:57:26 EST 1998


Jonathan Witchell wrote:
> 
> Hello!
> 
> I'm just a visitor on this newsgroup and am relatively ignorant about
> things microbiological. I'm helping a friend without internet access to
> find the meaning of the phrase "mould-yeast dimorphism". He also needs
> an example of a fungus that exhibits it.
> 
> I hope all this makes sense. I've spent a couple of hours searching the
> net with no success, so I hope someone here can help!
> 
> Thanks in advance,
> Jonathan Witchell, Kent, UK.

"mould-yeast dimorphism" is a phenomon which quite a number of fungi,
particularly pathogens, exhibit.  These organisms switch between a mould
- thread-like or mycelial - growth habit where growth occurs at the tips
of the hyphal threads and yeast growth habit where cells are roughly
spherical and growth is radial followed by the budding or division to
form new cells.  The trigger to switch is environmental.  In the
human/animal pathogens like Histoplasma capsulatum or Mucor rouxii the
conditions which favor yeast for are some or all of the following
(depending on the specific fungus): high CO2, low O2, high temperture
and rich growth medium.  The opposite conditions favor moulds.  As you
might guess, in an animal host, you usually finf the yeast form and in
the soil you find the mould.

BTW, look under dimorphic fungi and also remember that on this side of
the pond, mould is spelled mold which might influence your number of web
hits!

*   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 nmsu.edu    *



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