What Can Cause A Change In Antibiotic Resistance For A Bacterium?
Posted on May 06th, 2009 in Antibiotics
Angela W asked:
I have to come up with a project with my microbiology course. I wanted to create an experiment using antibiotics. I was thinking of changing the media it grow in and adding various concentrations of an amino acid to see if it would affect the bacterium's resistance or susceptibility to the antibiotic? Would that work?
I have to come up with a project with my microbiology course. I wanted to create an experiment using antibiotics. I was thinking of changing the media it grow in and adding various concentrations of an amino acid to see if it would affect the bacterium's resistance or susceptibility to the antibiotic? Would that work?
I can't think of anything else I could add to the medium that would affect antibiotic resistance.
If anyone has any advise, I would greatly appreciate it!
Thanks!
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Tags: Bacterium, Susceptibility
This post has 2 comments
May 10th, 2009
1) Waiting. Bacteria spontaneously produce new mutations.
2) Multiplicity. Use a number of petri dishes.
3) Certain chemicals are mutagenic. They increase the rate of mutation e.g. in bacteria. Such a chemical would be toxic, dangerous and not easy to get.
4) Using a low concentration of antibiotic, maybe.
May 11th, 2009
It probably isn’t a good idea to use an actual antibiotic, but the principle of developing bacterial strains with resistance to an inhibitory chemical would make a good experiment. The only thing to watch out for is the amount of time it might take to get results - you might need dozens of generations.
Instead of an antibiotic, you could demonstrate the principle of resistance by developing a bacterial strain that is less sensitive to a metal such as nickel or copper, or some other substance that is generally toxic to bacteria. Maybe you could actually develop a bacterial strain that could clean up heavy metal pollution!!
To do this, you would have to start out with multiple agar plates that contain a range of low concentrations of a chemical that inhibits bacterial growth, and grow the cultures until colonies form. Verify that the colonies are actually the bacteria you intended to grow, and then select the bacteria from the medium with the highest concentration of the inhibitory chemical. Next inoculate several new plates that have slightly higher concentrations of the inhibitory chemical than before, and do this sequentially may times, while steadily increasing the concentration of the inhibitory chemical.
For the final experiment, you could then make up a series of gel plates that have concentrations of the inhibitory chemical that span several orders of magnitude, including a plain agar plate with no inhibitory chemical. Make up several replicates for each concentration. Then inoculate each plate with the original bacterial strain and the new strain of bacteria. Mark the gel plates so you can tell which colony is which, and compare the growth rates (colony sizes) of the two strains.
For analysis, you could plot a graph of colony sizes or colony numbers for each bacterial strain as a function of the concentration of the inhibitory chemical. The graphs should have very different slopes or absolute values if the experiment worked.
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