Help: A Level assessment

Vicki Steven m.steven at uws.edu.au
Tue Mar 23 15:04:54 EST 1999

In article <7d6g0n$qgb$1 at yama.mcc.ac.uk>, "Eric Opara"
<mcai8eo2 at stud.umist.ac.uk> wrote:

> Hi, struggling to do my assessment, in desperate need of any help.  here is
> the the problem:-   To design and be able to carry out an experiment to
> determine the effect of the concentration of a disinfectant on the growth of
> bacteria.  Where bacteria grow in a glucose medium.

This is basically a simple MIC expt - minimum inhibitory concentration
which will be written up in any basic micro book.  I recommend using a
doubling dilution series ie 10 tubes containing 5 mL glucose broth ; add 5
mL disinfectant to Tube 1(1/2 strength); take out 5 mL and transfer it to
tube 2 (1/4 strength) etc down to tube 9.  Tube 10 is a control. Inoculate
all 10 tubes with your chosen organism. After incubation you can either
compare OD using a spectrophotometer or simply make a visual assessment
based on turbidity - growth/no growth.  The MIC is the highest dilution
showing no growth.
Hope this helps.
Technical Officer, Microbiology
UWS, Hawkesbury

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