[Microbiology] Problems with E. Coli

Nachiket Vaze via microbio%40net.bio.net (by nachi1981 At gmail.com)
Tue Nov 28 12:05:50 EST 2006


    I am a grad student in Bioengineering working on a sterlization project.
The method that I use for judging the extent of sterlization is the Plate
Count method. Since I have NO undergrad background in Micro, I am
struggling. I have a few questions to ask, so please bear with me.

Q1) After one experiment I found 2 types of colonies growing on the plate.
One was distinct E. Coli like ( round and whitish) The other was like
smudge, but with distinct colonies. So I used EMB agar to test them and to
my surprise, The smudge colonies gave a green sheen and the E. COli looking
colonies did not. How is that possible?

Q2) Another weird thing is that I had streaked an EMB late from an isolated
E. COli colony a few days ago and the plate did show Green sheen but after I
taped it and kept it in the fridge for a few days, the sheen disappeared. Is
that supposed to happen.

Q3) My lab is looking at different methods to judge the degree and the
mechanism of Sterlization i.e. microbial killing. Can anyone suggest
something other than Plate Count.

PLEASE help!!!


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