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Department
Biology
Course
Biology 2290F/G
Professor
Prof
Semester
Fall

Description
The effect of alcohol concentration on the growth of Micrococcus luteus and Pseudomonas aeruginosa Matthew Andrade, Maneet Dhillon, Vineet Gupta, Vivian Lac, Noeline Rasanayagam, Shagana Visuvanathan, and Jialin Wen Department of Biology, The University of Western Ontario, London, ON, Canada N6A 5B7 INTRODUCTION: Antibacterial products and disinfectants are used incessantly and deemed essential in today’s society. Antibacterial products inhibit the growth and reproduction of bacteria, essentially killing them. They are used domestically to disinfect homes from harmful bacteria and in medical clinics and hospitals where cleanliness and a bacteria- free environment are necessary for the health of patients. However, antibacterial use has become a controversial issue in the scientific world; its use has countless risks associated with it. Infants consistently exposed to antibacterial agents may experience an abnormal maturation of the immune system because it has not been exposed to necessary bacteria to allow maturation, leading to a possible rise in allergies among children (Levy 2001). Furthermore, extensive use of antibacterial products in domestic and health care facilities may actually lead to bacterial resistance to certain agents and cross-resistance to antibiotics may be a result (McDonnell and Russell 1999). Although there are many risks associated with the use of antibacterial products, they continue to be popular, which leads to the question: How effective are antibacterial products at eliminating bacteria truly? Are products with higher concentrations of antibacterial agents more effective? These particular questions were explored in this experiment, where the experimental bacteria, Micrococcus luteus (Schroeter) Cohn and Pseudomonas aeruginosa (Schroeter) Migula, were exposed to Purell and various concentrations of alcohol. P.aeruginosa is commonly found under nails, while M.luteus is found on flora of human skin (Baron 1996). Moreover, both bacteria are also customarily found on household items and in dust (Madigan and Martiniko. 2005). Due to the nature of the environments they commonly inhabit, P.aeruginosa and M.luteus are ideal bacteria for this experiment because they are the target of many antibacterial products. Alcohol and Purell (alcoholic hand sanitizer) were the antibacterial agents chosen because alcohol is a key ingredient in many antibacterial products available in the market today. Objective: To determine the effect of Purell and various concentrations of alcohol on the diameters of the zones of inhibition of Micrococcus luteus and Pseudomonas aeruginosa. Hypothesis: The different alcohol concentrations will have an effect on the diameter on the zones of inhibition of Micrococcus luteus and Pseudomonas aeruginosa. Prediction: The diameters of the zones of inhibition of Micrococcus luteus and Pseudomonas aeruginosa will be larger when treated with higher alcohol concentrations when compared to the diameter of the zones of inhibition of the control (0% alcohol). METHODS: • Samples of M. luteus and P. aeruginosa were vortexed with LB broth in Eppendorf tubes and the mixture was spread onto 30 agar plates per bacterium. • Each agar plate had a well cut out in the center with a diameter of 6.3 mm and was filled with one of five treatments: deionized water (control), 40% alcohol, 50% alcohol, 65% alcohol and Purell hand sanitizer (65% ethanol content). Each treatment had six replicates. • The plates were incubated in the dark at 27 ̊C for 24-48 hours. • The diameters of the zones of inhibition were measured in millimetres using Vernier Calipers. STATISTICALANALYSIS: Data in this study were analysed by a one-way analysis of variance (ANOVA) to compare the effects of each treatment on P. aeruginosa and M. luteus. Additionally, Tukey’s HSD test was conducted for each bacterium to identify any differences among the means (IBM SPSS Statistics 21 2013). Fig. 1. Effect of various alcohol concentrations on the mean ± SD of diameter of zone of inhibition (mm) of Pseudomas aeruginosa and Micrococcus luteus. Means followed by the same letter within each variable are no
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