Identification of a nasty fungus

David Geiser dgeiser at mendel.berkeley.edu
Mon Jan 29 01:07:26 EST 1996


In article <199601281919.LAA26523 at net.bio.net> Dan Ebbole,
dje0282 at VMS1.TAMU.EDU writes:

>2.  Contamination problems can occur with virtually any conidial fungus
>from time to time.  But the above story is certainly a gross exaggeration
>if not an outright fabrication.  We have a number of fungal labs in the
>building my Neurospora lab is in.  No other lab has EVER reported
>Neurospora contamination.

My guess is that labs may be the source of a contamination, but they are
really not the problem.  I'll bet the problem is usually a bad
ventilation system,  or a constant temperature room that's too humid, or
lots of old cultures,  plant material or food left lying around. 
Everyone will
occasionally get an odd colony growing on a plate,  but I think real
problems are caused by the facilities.

  On the other hand, my lab and almost every other
>lab has often seen contamination from Aspergillus (probably from the
>environment, not the Aspergillus lab on the floor?).  

Most likely the environment.  I worked with wild-type strains of 
various Aspergillus spp. in an Aspergillus genetics lab,  which was
a great source of paranoia.  I shared the incubator with everyone else
in the lab,  most of whom worked with strains that required nutritional
supplement,  and most people did their sterile work right on the
benchtop.  I only know of one instance where one of my strains
was certainly growing on someone else's plates.  I occasionally found 
an obvious lab strain growing on one of my plates,  but this was very 
rare. We were in a new building with excellent ventilation,  and I'm sure 
that helped.   The "Aspergillus" contaminants I've seen have almost always
been A. fumigatus,  A. niger,  or Penicillium,  so one should not
blame the A. nidulans lab down the hall because of an Aspergillus
contaminant.

>The idea that Neurospora is a major contamination problem is a myth as far
>as I can tell.  With the same care in handling, Neurospora is no more of a
>contamination problem than the Aspergilli.

I think this is true.  Working on Aspergillus next door to a Neurospora
lab,  I don't remember ever seeing or hearing about Neurospora as a
contaminant.  I'm sure that any Neurospora scientist worth his or her
salt would not grow conidiating strains on petri dishes and let them
get out of hand. The contaminant reported  that started this thread was 
from  New Orleans,  LA,   and Neurospora is commonly isolated from sugar 
cane  fields in Southern Louisiana.  Maybe Neurospora (more likely its
anamorph) is more of a contamination problem in Louisiana than elsewhere.


Dave Geiser



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