Zone of Inhibition Growth
Country: United States
Date: August 2008
What does it mean when you find isolated bacterial
colonies growing in a zone of inhibition?
There is variety in every population. In bacteria some differ in
their tolerance for antibiotic. Most of the bacteria within the
zone of inhibition have been killed or are being repelled from
growing in the area of the antibiotic, but the ones you see are
resistant to it. If you were to take one of those colonies and
repeat the experiment, you would probably see that is no zone of
inhibition because all of the offspring of those original bacteria
are genetically the same as the original.
They are probably genetic mutants that are resistant to the antibiotic
or contaminating bacteria that are not sensitive to the antibiotic.
Ron Baker, Ph.D.
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Update: June 2012