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Intel ISEF 2013 Finalist Profile

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The Effect of Heat Shock Protein 33 on the Development of Sodium Hypochlorite Resistance in Escherichia coli

Kathryn Morris

New Prague Senior High School, New Prague, MN

I tested to see if Heat Shock Protein 33 (HSP33) is one of the causes of bleach resistance in E. coli bacteria. I plated a wild type and a mutant (HSP33 lacking) strain of E. coli onto agar plates and then placed 4 filter paper disks onto each plate. I pipetted 20 &#956;l of bleach onto each of the disks and then incubated the plates. After incubation, I measured the diameters of the zones of inhibition (the bare circles around the disks. Using a sterile loop, I selected a colony of resistant bacteria from the edge of the zone of the inhibition. I then plated these bacteria on a TH plate to incubate overnight. This made up the resting round of my experiment. I repeated these steps for 5 rounds using 5 different concentrations of bleach. I calculated an average percent change from the 1st round to the 5th round and used the percent change to compare the mutant to the wild type strain of bacteria. The greater the percent change, the greater the resistance induced. The wild type bacteria induced a slightly greater resistance than the mutant bacteria at most concentrations. This shows that HSP33 is a cause of resistance to bleach in E. coli, however it is not the only cause. I believe my experiment shows that E. coli has evolved many proteins to help it survive under oxidative stress.

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