9. Why do some populations of bacteria become resistant to antibiotics?


General Thoughts

You are facing a bacterial infection that won't respond to normal antibiotic treatment. How does that happen? Is that a problem in the world today? We discuss this in Emerging Diseases and we discussed the underlying principle of natural selection explicitly in both Out of the Rainforest and Marooned in the Galapagos . Before planning for and interpreting this lab, you might want to learn more about mutations and DNA. We will discuss these in more detail in Family Reunion, so you really don't have to delve much into the topic for now. If you know that DNA is the genetic material that is the "blueprint" for organisms' characteristics, that changes in the DNA (mutations) lead to changes in the characteristics and that natural selection then goes to work, you have the necessary basics. Your textbook can provide relevant information.

A bacterial infection develops that is resistant to antibiotic treatments in areas exposed to sunlight while areas not exposed to sunlight are not suffering from the same ailment (ie. antibiotic treatments are working to clear it up). We discussed light and its characteristics in Rainbow Connection. You need to consider all of the electromagnetic spectrum, not just the visible portion. There is no mention of getting sunburned so you need to learn about the effects of radiation on the bacteria not the one's infected.

Do you have those infected to test in lab? Well this has not proved practical in this class (especially when there are hundreds of you). Besides to test what is happening to the bacteria, you don't really need the one infected, you need a place to grow and test the bacteria. So scientists "culture" (grow) the bacteria on a medium, such as agar (or in nutrient broth), under various conditions (tests, treatments) and see what happens to the bacteria (do they grow or don't they).

Are the principles of population growth related to this lab in any way? What type of growth curve will the bacteria exhibit under these lab conditions? Does that explain why you need only wait 24-48 hours before you see results? What will you be looking at?

Hints and Suggestions:

Valuable Concepts

Mode of Action Population Growth
Mutation Selective Agent
Natural Selection UV

 

 

Some Bad Hypotheses

Some Worthwhile Web Sites


source
from Dr. Ulrich Melcher's on-line Molecular Genetics course at OSU
from Dr. Ulrich Melcher's on-line Molecular Genetics course at OSU

source
the bacteria exhibit at the Museum of Paleontology at the University of California, Berkeley

source
an introduction to bacteria for kids, in case you want to see what elementary schools are teaching from Eureka Science Corp.

source
a lengthy article from faculty at University of Montreal in the Science Tribune - a good source!

source
from the CDC - expresses concern about world problem
from the CDC – discusses current trends and issues regarding Antibiotic/Antimicrobial Resistance in today's world
Types of mutations, causes, repair and evolutionary importance from the MIT Hypertextbook Central Dogma Directory
You may have looked at this site getting ready for Lab 5, take a look again - nice imagery and video of bacteria in various situations.

Some Articles found by ProQuest

R. Lewis. September 1995. The Rise of Antibiotic-Resistant Infections. FDA Consumer. (On WWW, not Pro-Quest)

Pre-lab

This lab begins a series of labs where you will be looking at and working with DNA. You might want to review the structure of DNA from lecture notes or the textbook. You should also do some reading about antibiotics and bacteria either on the WWW or in your textbook. One last point, neither the ASPCA nor OSHA let's us bring cats into the lab!!

Activities:

You may do this lab's pre-lab activities from any WWW connection, if you follow the directions so that the information is sent to your TA. If you aren't able to get the Athorware programs to run on your computer, you will have to view the WWW sites or use a textbook and have the person on duty in the LRC sign your planning form.

  1. Look for information on the WWW that describe how the antibiotics Streptomycin, Ampicilin, and Kanamycin work and how UV radiation can play a role. You can

    • Search for sites on your own (it's easy), then discuss what you found with a TA in the LRC or e-mail your answer to your TA
    • Or you can complete the prelab, which will direct you to some sites and record your answer.

  2. Complete the prelab Inoculating an agar plate

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