Name: Wan M.
In microbiology, most people like to use "Bacto Agar".
Why are they using "Bacto Agar" instead of plain agar which is also much
cheaper as listed in the product catalogue? Thank you.
I am not sure but I seem to remember that Bacto Agar
is more purified, so that it contains less traces of
compounds other than Agar. This is important if you
want to produce plates that are selective. This means
you leave out certain nutrients, because you want to
select for those organisms that can grow without these
(they will have to be able to produce the nutrients
themselves). You wouldn't be able to do that if the
Agar was not sufficiently pure, since trace amounts of
the nutrients would be sufficient for other organisms
to grow as well. In that case your plates would not be
From experience I also know that plates poured with
Bacto Agar are more transparent which makes them
easier to look through. Microbiologists like to view a
plate from the bottom, which decreases the risk of
contamination or condense water to smear the plate.
Dr. Trudy Wassenaar
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Update: June 2012