Application:
5.2.A2: Evolution of antibiotic resistance in bacteria. Objectives:
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Antibiotics are chemicals produced by microbes that either kill (bactericidal) or inhibit the growth (bacteriostatic) of bacteria. Antibiotics are commonly used by man as a treatment for bacterial infections (not effective against viral infections). In a bacterial colony, over many generations, a small proportion of bacteria may develop antibiotic resistance via gene mutation.
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Shortly after development of antibiotics (e.g. penicillin) nearly all bacteria were killed during an application of antibiotics
- some variants of bacteria had a heritable trait that gives them resistance to antibiotics
- the resistant bacteria have higher rates of surviving and reproducing
- resistant bacteria pass on the trait of antibiotic resistance to their offspring
- in each following generation the percentage of antibiotic resistant bacteria increases
- that is, the frequency of the antibiotic resistance alleles increases over time
- As predicted by evolutionary theory, natural selection produces gradual changes in traits in response to changes in the environment
- Resistance can be passed onto other pathogenic bacteria, creating more species of resistant bacteria.
- Some examples of bacteria known to develop resistance are Treponema pallidum which causes syphilis and the bacteria that causes tuberculosis (Mycobacterium tuberculosis)
Nature of Science:
5.2.NOS: Use theories to explain natural phenomena- the theory of evolution by natural selection can explain the development of antibiotic resistance in bacteria.
Objectives:
5.2.NOS: Use theories to explain natural phenomena- the theory of evolution by natural selection can explain the development of antibiotic resistance in bacteria.
Objectives:
- List three trends that have been observed in the development of antibiotic resistance.
- Use a graph to illustrate antibiotic resistance over time.
Evolution occurs at both the micro and macro levels. Macroevolution is the eye-catching form, where we see species changing into dramatically new ones. This process though takes time and is not directly observable.
Microevolution, while less “glamorous” is no less interesting. Indeed, it has applications that are amongst the most serious concerns in health, medicine and agriculture. This is the ability of populations of bacteria, protists, fungi, insects or plants to evolve resistance to antibiotics, drugs, pesticides and other chemicals used to control them.
The resistance of bacteria to antibiotics has occurred at an incredible rate, as the image below shows:
Microevolution, while less “glamorous” is no less interesting. Indeed, it has applications that are amongst the most serious concerns in health, medicine and agriculture. This is the ability of populations of bacteria, protists, fungi, insects or plants to evolve resistance to antibiotics, drugs, pesticides and other chemicals used to control them.
The resistance of bacteria to antibiotics has occurred at an incredible rate, as the image below shows:
What is particularly concerning about this is shown in the following graph – the number of antibiotics being developed approved continues to decline, which leaves fewer options for treatment.
Understanding the process of evolution is critical to estimating the number and type of new drugs that are needed to combat them. It is thus necessary to understand that antibiotic use represents a very strong selection pressure. Given the reproductive potential of bacteria (more offspring are born than can survive) and the variation that is possible (through both mutation and horizontal gene transfer) it should therefore come as no surprise that populations rapidly evolve resistance. Evolution and natural selection are thus not the dated musings of a 19th-century naturalist, but of critical importance to health problems of the 21st-century: in the US alone, over 2 million illnesses and 23,000 deaths per year are directly attributed to evolved resistance.
From an assessment perspective, antibiotic resistance in bacteria is a great example to use when responding to and extended response question on evolution/natural selection.
From an assessment perspective, antibiotic resistance in bacteria is a great example to use when responding to and extended response question on evolution/natural selection.