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[Microbiology] Re: phenol red fermentation tests

GreenieLeBrun via microbio%40net.bio.net (by GreenieLeBrun from hotmail.com)
Tue Feb 20 22:53:46 EST 2007

"Lisa Moore" <lmoore from usm.maine.edu> wrote in message 
news:mailman.24.1171993232.5139.microbio from net.bio.net...
>I teach a basic microbiology lab class and have included the phenol red
> fermentation test in the lab after the students do the
> oxidation-fermentation glucose test.  I am trained as a phytoplankton
> ecophysiologist, so I am not familiar with this test outside of teaching
> this lab.  From the various lab books and websites that I have looked
> at, the test is done in test tubes under aerobic conditions.  My
> question is whether a non-fermenter can oxidize the sugars (such as
> lactose and sucrose) and turn the medium yellow (indicative of acid
> production), thus giving a false positive?  It seems to me that this is
> possible, making the test rather limited.  Of course, I could be missing
> something in understanding the protocol or chemistry behind the test.
> If someone has a quick answer or a good reference, I would appreciate
> the help.
> Thank you,
> Lisa
> Lisa R. Moore
> Assistant Professor
> Department of Biological Sciences
> University of Southern Maine
> 96 Falmouth Street
> Portland, ME  04103
> email:  lmoore from usm.maine.edu
> phone:  (207) 780-4261
> fax:  (207) 228-8116

Never heard of the phenol red test in relationship to microbiology, do you 
mean the methyl red (MR)test that is often performed in conjunction with the 
Voges-Proskauer (VP) reaction to help distinguish E.coli from other 

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