MadSci Network: Microbiology

Re: how to identify mold

Date: Mon Jan 11 16:55:59 1999
Posted By: Hurley Shepherd, Agricultural Research, USDA Southern Regional Center
Area of science: Microbiology
ID: 914979935.Mi

There are many different kinds of molds or "filamentous fungi" and it 
really takes an expert to be able to identify all of them to the species 
level.  On the other hand, if you just want a scientific name (a correct 
one at that) for molds you may find around your house, that is a little 
easier.  A few fungi account for most of the ones you see normally.  
Greenish-bluish ones are probably either from the genus Penicillium if the 
colony has a white border around it, or Aspergillus if 
it doesn't have a white border around the colony.  A black-looking colony 
is probably in the genus Rhizopus (commonly called "bread mold" 
although it is not the only fungus which grows on bread and it also grows 
other places besides bread) or Neurospora.

To aid in your identification (and see some neat stuff) a microscope 
helps.  It doesn't need to be very powerful either, probably the kind you 
have at your school.  Put a drop of water on the mold and mix it gently 
with a toothpick. (It may take a couple of tries to get the right amount 
of mixing.  Some molds give up their secrets more easily than others.) 
Then put some of the liquid on a slide and look at it 
under the microscope.  What you will see are the mold spores and the spore-
forming structures (the sporangia), which give a more certain 
identification of the mold than just the colony color. (If you just see a 
big black blob, you probably have too much stuff.  Look at the edge of the 
blob and see if you can make out individual structures, or try again with 
less mixing.) This is the first thing a mycologist would do also.

To find out what you have, most basic books on fungi (and some general 
biology books) will give pictures of common fungal spores or sporangia.  I 
use a book called Beginner's Guide to the Fungi by C. L. Duddington (Drake 
Publishers, New York, 1972).  
There is a new book with much of its information online called The Fifth 
Kingdom (which refers to the five major groups of living organisms-plants, 
animals, bacteria, single-celled organisms, and fungi) which can be found 

If you have something you can't identify in this way, or if you want to 
know the complete scientific name (genus and species), call up the nearest 
college or university Biology department and ask if there is a mycologist 
on the faculty.  I am sure they will be happy to help you with a school 
project or to just satisfy your curiosity.

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