Date: Mon Jan 2 07:37:58 2006
Posted By: Lynn Bry, MD/PhD, Dept. Pathology, Brigham & Women's Hospital, Harvard Medical School
Area of science: Microbiology
Hi Ashley -
There are a number of websites with information about different species of
molds, including images and drawings that can help you identify bread molds.
Doctor Fungus is one of my favorites.
You can also locate "Mycology" textbooks through your local public library, or a
university library, which will give you the same information in printed form.
If the library doesn't have a textbook in their collection, ask one of the
librarians to help you locate a book via interlibrary loan. A few to try are:
When observing mold colonies on bread, you should define the following
To speciate molds we commonly use a microscope to observe the fine structure of
hyphae and fruiting bodies/spores produced. Biochemical assays are also commonly
used. However, as you can see from above, simple observation of the mold colony
can give you a good idea of the type of mold growing.
- What is the color of the mold? Some molds have hyphae (or branching
elements) that are non-pigmented. These types of molds are called hyaline molds,
whereas others (commonly the ones you see on the bathroom tiling) are
"demetiaceous" or darkly pigmented - commonly black in color.
- Is the center of the mold a different color from the edges? Many
light-colored molds, also called
Hyphomycetes, produce pigmented spores as they grow. For instance,
Aspergillus fumigatus produces a green center (coloration from the
spores) with a white edge. The white edge is called an "apron" - this area has
just hyphal elements (branches of mold filaments), that have not yet developed
Pencillium species tend to produce bluish-colored spores, while the
spores produced by
Aspergillus niger are black in color.
- Copious quantites of white-grey, cottony material suggests species of
Rhizomucor. In the lab, we refer to these species as "lid-lifters" as
they will push the lid of a Petrie plate over if left to grow unchecked (for
this reason, we tape the lid shut if we isolate one of these).
Lastly, molds need to be handled very carefully. The mold on bread is capable
of causing infections, particularly in people with weakened immune systems,
individuals with respiratory problems such as asthma, or in the very young or
You should do the following when working with molds growing on foodstuffs:
- Wear gloves and an outer smock (or lab coat) when handling molds. Throw
gloves our after use; smocks should be soaked in 10% bleach before washing and
- For observation, place materials in a clear plastic or glass container that
can be sealed.
- Decontaminate all areas on which you have worked with the molds, or have
placed molds, with a 10% bleach solution (to kill spores; 1 part bleach to 9
parts water). You can place this solution in a spray bottle to clean
contaminated surfaces. Let the solution sit for ~10 minutes before wiping the
- Foodstuffs containing molds can be fully soaked in 10% bleach for ~1 hour
prior to disposal of the materials.
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