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Name: Joey
Status: student
Grade: N/A
Location: N/A
Country: N/A
Date: N/A

My 6th graders are studying fungi. We have innoculated various media with spores from mold grown on bread, cheese, fruits, etc. Did I have to altoclave the growing media before it was innoculated? We are using 4 growing mediums.... mashed potatoes with water, mashed bananas with water, tomato sauce, and a yeast solution (yeast and water, no sugar) covered with moistened bread.

We have fielded this question before. Check the NEWTON BBS archives.

Sterilizing the media is always a good technique, but it seems that your project does not require it. My feeling is completely different. If you are not qualified to identify the numerous hazardous and extremely hazardous fungi and bacteria that may be growing on your plates, you should not perform this activity, in my opinion, in a classroom setting. Take the precautions of not getting your students sick and sterilize everything when you are done.

If you are qualified, I apologize, but others will be looking at this note when it is posted.

Steve Sample

If your media aren't autoclaved you may get some contamination with bacteria. Most bacteria are inhibited by acidic conditions however, so the tomato based media may be less hospitable to bacteria. Let me know how your experiment goes-I'd be intersted to know your results.


Dear Joey,

Basically, autoclaving would sterilize the media prior to inoculation. Not autoclaving permits the growth of other bacteria and fungi already present in the media.

If you only wanted one kind of spore per experiment and controls without any fungi, then autoclaving would have been useful.


Anthony R. Brach, Ph.D.

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