Central Christian AP bio class uses a unique science experiment to explore e. coli bacteria

Central Christian AP bio class uses a unique science experiment to explore e. coli bacteria
Dave Mast

The AP bio class at Kidron Central Christian School recently studied e. coli. The science experiment was designed to provide some hands-on work for the students.


Most people would run screaming from the table if they found a strain of escherichia coli bacteria, better known as e. coli, anywhere near what they were handling.

However, the AP biology students at Kidron Central Christian School actually went looking for it during a unique experiment.

The junior AP biology class, taught by Jolene Jaquet, recently visited a farm, collected swab samples from cows and began the process of testing those samples in the school lab.

The test subject was e. coli, which has made its way into the news recently with a large amount of beef being recalled due to an e. coli outbreak. Over the years e. coli bacteria also has been found in lettuce, spinach and other foods consumed by humans.

The class performed anal swabs on some young cattle with the hopes of finding the e. coli bacteria, of which there are many strains.

“A lot of schools don’t do this type of experiment because there is some fear in working with bacteria, and it can be a little intimidating, but I believe that when you treat bacteria with respect and take the proper precautions, it can be such a tremendous learning tool for the students,” Jaquet said.

When the students did manage to identify their bacteria as e. coli, they set about working with four different antibiotics to see which one provided the best resistance to their particular strain.

The students were working with Bunsen burners to sterilize their tools, inoculating loops, bacterial plates, microscopes and other delicate science equipment.

“I am using this as a way to give the students a very hands-on way of deciphering which strain of e. coli they have and what type of antibiotics will work to cure it most effectively,” Jaquet said. “The old idea of giving everyone penicillin doesn’t work anymore because these strains have evolved and gained greater resistance to antibiotics, so finding ways to combat these different strains of bacteria is an ongoing process because it is forever changing, so it will be interesting to see what kinds of resistances we encounter.”

The students teamed up and explored their swabs by plating them and allowing what they hoped was the e. coli strain to develop on bacterial plates. Once that was accomplished, the teams added four different antibiotics to see how the bacteria responded.

With the bacteria plates containing the bacteria and with the antibiotics in place, the groups could identify if and how well each antibiotic worked by noting how the patterns appeared on each sample.

“There will be bacteria everywhere on the plate, except it will be clear where the antibiotic worked,” Jaquet said. “We can also test how effective and potent each antibiotic works to kill the bacteria by the size of the clear ring around each sample. Therefore I’ll ask the students, if they were the doctor or veterinarian, which one would they prescribe to a patient based on their results.”

Penicillin and ampicillin are common antibiotics to use in animals while azithromycin and tetracycline were the two used in the experiment that are aimed at humans.

While the purpose of the experiment was to identify e. coli and find a working antibody by collecting data and exploring the resistance levels of a particular strain, Jaquet said engaging in the skills necessary to do so is the main objective for the students to learn.

“It’s about dealing with bacteria safely and learning how to use the equipment properly,” Jaquet said. “The process is proven, and they are learning clinical techniques in investigating bacteria. This gives them some real-world experience in a very controlled element. Developing those skills and gaining understanding on how this works is exciting to see, and they are gaining some great awareness on the public health dangers that are out there. Having them be so hands-on definitely helps this stick with them in ways that they would never get simply reading about it or having me talk about it.”

Eventually the students will write a lab report detailing how bacteria transfers resistance, how it survives and how it spreads. They also will delve into the world of statistics in developing their theories and results.

Jaquet said there is one other important message she likes to drive home.

“Once we are able to identify the bacteria and an antibiotic is prescribed, it is absolutely necessary to take the entire prescription, even though a person might start feeling better,” Jaquet said. “When people don’t take the entire prescribed dosage, that is the kind of thing that begins to lead to resistance, the one that allows that bacteria to survive and grow and to gain resistance. All of this is very relevant to what is going on in the world today, and this is something they can visualize in gaining some valuable knowledge.”

The students eventually ran gram staining on the bacteria, a type of staining technique for the preliminary identification of bacteria in which a violet dye is applied, followed by a decolorizing agent and then a red dye.

“Even if we have bacteria, it isn’t necessarily going to be e. coli, so that helps us identify which type of bacteria we have,” Jaquet said. “These students have already done gram staining as freshmen, so it will be a bit of a review, but it is great practice in differentiating between types of bacteria.”

The other part of this experiment is the actual art of going to a farm and doing anal swabs on living cows, something no student will soon forget, but that is the sort of thing one must do in the name of science.

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