The Effects of Black Tea on the Growth of E. Coli Bacteria Cultures

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  • Topic: Tea, Tannin, Green tea
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The effects of black tea on the growth of E. coli bacteria cultures Kierstin Barker, Melissa Bischak, Jackie Tyszkiewicz, Errin Enany September 25, 2012
Abstract: This study was carried out in order to investigate whether black tea has antimicrobial properties as stated in Steven Johnson’s The Ghost Map. If tea does have antimicrobial properties, then it could aid in warding off waterborne diseases. We believed that if black tea is steeped in boiled water, then the amount of bacteria exposed to this solution would decrease. We expected to see no difference in the amount of bacteria exposed to the black tea solution. Tannic acid, black tea, boiled water, and a tetracycline antibiotic were tested for their zones of inhibition in order to determine antimicrobial properties. Our results stated that tea does not contain tannic acid but does contain tannin and therefore does not have antimicrobial properties that contain tannic acid based on the results of this experiment. Introduction:

In the novel: The Ghost Map, written by Steven Johnson, Johnson refers to the idea that tea has antimicrobial properties and that it could possibly have influenced people’s risk of contracting infectious diseases such as cholera (Johnson, 2006). Traditionally, people drank tea to improve blood flow, eliminate toxins, and to improve resistance to diseases (Dufresne and Farnworth, 2000). Tea has been shown to have a wide range of physiological and pharmacological effects such as having antimicrobial properties, inhibiting malignant cells, and simply leaving the drinker feeling refreshed (Hamilton-Miller, 1995). Black tea contains amounts of tannic acid. Tannic acid is a commercial type of tannin, which is a bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids and has antimicrobial properties which could possibly aid in warding off waterborne diseases (Yildirim, 2000). Could some people in the city of London actually have been saved from the fatal cholera disease due to their preferred drink of tea? If tea actually does have antimicrobial properties, then it could possibly provide some explanation as to why some people were not affected by this waterborne disease as seriously as others. So, our primary question is, “Does black tea decrease the amount of live bacteria in a solution?” In order to test this question, we have devised hypotheses and experiments to see if black tea actually does stunt bacterial growth and whether tannic acid helps aid in this process. While making observations, developing questions, designing an experiment to test hypotheses, and analyzing data, we also want to demonstrate our proficiency in using the scientific method throughout this study. We believe that if black tea is steeped in boiled water, then the amount of bacteria exposed to this solution will decrease. We expect to see no difference in the amount of bacteria exposed to the black tea solution. If we are able to accept our alternative hypothesis, then the claims that Steven Johnson makes in The Ghost Map could be plausible and tea with tannic acid could have possibly helped ward off waterborne diseases during this particular outbreak in London. By testing antibiotic, tannic acid, and black tea solutions on prepared agar plates covered in E. coli bacteria, we predict to observe the different effects that each solution emits based on the zone of inhibition for each type of solution. Materials and Methods:

This experiment was carried out on September 11, 2012. In order to carry out such an experiment, many different materials were used. Two 200 mL beakers were each filled with 200 mL of deionized water. Using a Bunsen burner, both beakers of water were heated until boiling at 100⁰C. Three agar plates were prepared with 100 microliters of E. coli bacteria. This amount was measured using a micropipette. The bacteria were then spread around the...
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