Breeding Antibiotic Resistance into E. coli and Removing the Resistance

The purpose of the experiment was to determine whether the bacteria, E.coli, that acquired resistance to the antibiotics, Streptomycin, over generations would maintain the bacteria’s antibiotic resistance or if the bacteria would revert back to its original state of susceptibility. Three sets of bacteria were tested over nine days. For the first four days, or generations, the bacterium was treated with the antibiotic. The next four days, the bacterium was not treated with antibiotics. On the ninth day, the bacterium was again treated with the antibiotic. The researchers conducted two 2-sample t-tests to compare the zones of inhibition, or areas of non-growth, of the first generation to the fourth generation, and the first generation to the ninth generation. The zone of inhibition decreased from the first generation to the ninth generation, signaling that Streptomycin resistance was successfully bred into the bacterium. The zone of inhibition from the first generation was very close in size to the zone of inhibition of the ninth generation. These results demonstrate that antibiotic resistance was bred into the bacteria and the bacteria reverted back to its original state of susceptibility. The conducted experiment could, therefore, benefit researchers in the medical field. Instead of the constant application of antibiotics, such as Streptomycin, antibiotic resistance within bacteria could simply be decreased by eliminating the antibiotic from these antibiotic-resistant bacterial infections for a certain period of time.

Research Conducted By:

Brooke Hassig
Warren Mott High School

Sydni Jordan
Warren Mott High School