Mechanism for Antibiotic Resistance Discovered

Those of us born after World War II have take antibiotics for granted. Strep throat? Ear infection? Acne? Bronchitis? Not a problem. Take the full prescribed antibiotic dose and you are cured. The reality of antibiotic resistant bacteria however, disrupts that scenario. No longer can we always trust in a full recovery from a bacterial infection after completing the antibiotic regimen. Rather than continuing to create new and different antibiotics, the trend in research is to discover the mechanisms of antibiotic resistance in order to neutralize it.

How Some Bacteria Survive Antibiotics from ScienceDaily describes how researchers at the University of Illinois, Chicago, studied bacterial action in the presence of erythromycin and related antibiotics. These drugs incapacitate the bacterial protein factories, ribosomes. All cells have ribosomes which are the site of translation in protein synthesis. Erythromycin prevents newly synthesized proteins from detaching from the two subunits of the ribosome, thus preventing the bacteria from thriving. The researchers discovered, however, that these drugs can signal the bacteria to switch a bacterial gene on that enables bacterial release of newly synthesized proteins from the ribosomes. Thus, they effectively resist the drug in a process known as inducible antibiotic expression.

The article quotes one of the researchers

Combining biochemical data with the knowledge of the structure of the ribosome tunnel, we were able to identify some of the key molecular players involved in the induction mechanism. . . .We only researched response to erythromycin-like drugs because the majority of the genetics were already known. There may be other antibiotics and resistance genes in pathogenic bacteria regulated by this same mechanism. This is just the beginning.

How to Turn This News Event into an Inquiry-Based, Standards-Related Science Lesson

A manifestation of evolution, antibiotic resistance aligns with the Life Science standard of The National Science Education Standards, “Species acquire many of their unique characteristics through biological adaptation, which involves the selection of naturally occurring variations in populations. Biological adaptations include changes in structures, behaviors, or physiology that enhance survival and reproductive success in a particular environment.” Also related is the structure and function section of the standard: prokaryotic cell structure, the ribosome, and protein synthesis.

Ask students if they have ever had an ear infection or strep throat. What did they do about it? Lead them to disclose that they went to the doctor, were prescribed an antibiotic and took it for the full course, often 10 days. Ask if they were cured then, or did anyone suffer a recurrence within the next week or so? If yes, why? Then what did they do? Lead them to articulate the concept of bacterial resistance. Consider showing visuals of a typical animal eukaryotic cell side by side with a bacterial cell. This will highlight the size and structural difference, and enable student comprehension of how bacterial cells can colonize a eukaryotic cell. Make sure they understand the activity of the millions of bacteria cells a) consumes nutrients needed by one’s own healthy cells and b) produces waste that makes one sick.

If you’ve already discussed the characteristics of living things, cell theory and cell structure, lead students to recall the importance of ribosomes to all living cells. Ask, what might happen if the function of the ribosomes were disrupted? Students should reason that protein production would stop and the cell would die for lack of needed proteins. Inform them that this is the way some antibiotics work; they interfere with the bacterial cells’ ribosome function. (Prokaryotic and eukaryotic ribosome structure varies slightly allowing the eukaryotic ribosomes to remain unaffected.) Ask, what if the presence of the antibiotic signaled the bacteria to produce a protein (turn a gene on) that interfered with the drug’s ability to disrupt the ribosome’s work? Allow plenty of wait time for them to think this through logically. They should arrive at the idea of antibiotic resistance, even if they don’t use that phrase.

Allow students to read the first three paragraphs above and follow the links. The protein synthesis link however, is probably too advanced for middle school students and can be eliminated. Have them read the article How Some Bacteria Survive Antibiotics. Assess: what is an antibiotic? How do drugs like erythromycin work? What is inducible antibiotic expression? How might it be helpful to know the mechanisms by which bacteria resist antibiotics? Describe how antibiotic resistance is an example of evolution.

Here are some additional resources from the Middle School Portal 2 related to antibiotic resistance and bacteria: Introduction to Bacteria; Microbes: Too Smart for Antibiotics?; Microbes: What They do and how Antibiotics Change Them; and What’s making you sick?

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This post was originally written by Mary LeFever and published May 9, 2008 in the Connecting News to the National Science Education Standards blog. The post was updated 4/23/12 by Jessica Fries-Gaither.