By: Sapna Seth, Julia Feldman, & Ashley Elmore The Effect of Different Brand Name Disinfectants on the Amount of Bacteria Killed By: Sapna Seth, Julia Feldman, & Ashley Elmore

Which brand name disinfectant (CloroxⓇ, LysolⓇ, or Scrubbing BubblesⓇ) is most effective at killing bacteria? Null Hypothesis: There is no statistically significant difference in the amount of bacteria killed (zone of inhibition) when bacteria comes in contact with Lysol® Power & Free Bathroom Cleaner vs. Disinfecting Scrubbing Bubbles® Bathroom Cleaner vs. Clorox® Disinfecting Bathroom Cleaner vs. deionized water.

Alternative Hypothesis 1 If Escherichia coli K-12 is disinfected with different brand name disinfectants, then the Lysol® Power & Free Bathroom Cleaner will be the most effective at killing bacteria, because it contains hydrogen peroxide, a high level disinfectant, which means it will kill all of the bacteria except for a few bacterial spores by denaturing their proteins and lipids.

Alternative Hypothesis 2 If Escherichia coli K-12 is disinfected with different brand name disinfectants, then Clorox® Disinfecting Bathroom Cleaner will be the most effective at killing bacteria, because it contains two variations of quaternary ammonium compounds that will damage the bacteria’s cell membranes by denaturing their proteins and disrupting their permeability.

Alternative Hypothesis 3 If Escherichia coli K-12 is disinfected with different brand name disinfectants, then Disinfecting Scrubbing Bubbles® Bathroom Cleaner will be the most effective at killing bacteria, because it contains four variations of quaternary ammonium compounds that will damage the bacteria’s cell membranes by denaturing their proteins and disrupting their permeability.

Alternative Hypothesis 4 If Escherichia coli K-12 is disinfected with different brand name disinfectants, then deionized water will be the most effective at killing bacteria, because the deionized water would act as a hypotonic solution. There would be more water around the bacteria than inside, and water would flood into the bacteria until they burst, damaging the bacteria.

Summary Independent Variable: Brand of Disinfectant Used Dependent Variable: Amount of Bacteria Killed Quantitative Data ANOVA Test

Bacteria Bacteria are prokaryotic organisms. Escherichia coli K-12 is the type of bacteria used in this experiment. Escherichia coli K-12 is from the Enterobacteriaceae family.

Disinfectants Disinfectants kill bacteria by: Damaging cell membrane Disinfectants are substances, such as heat or chemical solutions, that are used to control the growth of microorganisms. Disinfectants kill bacteria by: Damaging cell membrane Denaturing enzymes and other proteins Damaging DNA

Chemicals In Disinfecting Scrubbing Bubbles® there is: Alkyl dimethyl benzyl ammonium fecting Bathroom Cleaner there is: n-Alkyl dimethylbenzyl ammonium chloride n-Alkyl ethylbenzyl ammonium chloride In Lysol® Power & Free Bathroom Cleaner there is: Hydrogen peroxide C10 Ethoxylated Alcohol

Purpose of Experiment Scrubbing Bubbles®, Clorox®, and Lysol® brands all claim that their products kill 99.9% of bacteria. This experiment was conducted in order to see which disinfectant is actually able to kill the most bacteria.

Materials & Procedure s. Incubate petri dishes for four days at 37°C. Measure zones of inhibition (mm). Properly disinfect materials.

Results

Conclusion Alternative hypothesis 3, which states, “If Escherichia coli K-12 is disinfected with different brand name disinfectants, then Disinfecting Scrubbing Bubbles® Bathroom Cleaner will be the most effective at killing bacteria, because it contains four variations of quaternary ammonium compounds that will damage the bacteria’s cell membranes by denaturing their proteins and disrupting their permeability.” is supported.

Conclusion (Cont.) Scrubbing Bubbles® is the most effective brand name disinfectant. Scrubbing Bubbles® damaged the bacteria’s membrane. The null hypothesis can be rejected, because the overall p-value is 0.0001, which is less than 0.05. Clorox® and Scrubbing Bubbles® are not statistically significant, since their p-value is greater than 0.05.

Experimental Errors and Unusual Results There was excess disinfectant around some of the chads. All of the zones of inhibition collected for deionized water were approximately 0mm except for one zone of inhibition which was 3mm.

Further Research Questions Is Disinfecting Scrubbing Bubbles® able to effectively kill gram positive bacteria? Which non-brand name disinfectant is most effective at killing bacteria? What is the effect of different brand name disinfectants on another common bacteria other than E. coli K-12?

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