Effects of Penicillin and Temperature on the Growth of Escherichia Coli

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Nicole Reardon
Biology 1520, Section P2
Effects of penicillin and temperature on the growth of Escherichia coli Abstract
Bacteria growth is known to be either augmented or impeded by a number of various factors; in this experiment, our group tested how E. coli is affected by penicillin as well as how different temperatures can affect bacteria growth. We know that antibiotics are generally specialized against certain types of bacteria—more specifically, some are most effective against Gram-negative, some against Gram-positive, and some are more broad spectrum. Given that E. coli is known to be a Gram-negative bacteria, our hypothesis was that Penicillin (narrow Gram-positive spectrum) would not be effective against E. coli; we also hypothesized that increasing temperature in the environment of the bacteria would be directly increase overall growth. We tested these hypotheses by preparing five different petri dishes, each containing cultures of the bacteria E. coli. In two of these dishes (set up identically), containing plain agar with no additional nutrients, we added small amounts of Penicillin to half the plate and water to the other half. We then observed the plates after one week’s time. For the other three plates we stored one dish at 4°C, one at 22°C, and one at 37°C; no antibiotics were added to any of these three dishes. Lastly, we then compared bacterial growth in the dishes that had been stored at different temperatures. Our final results indicated that Penicillin is not effective against E. coli because it is a narrow Gram-positive antibiotic that works by inhibiting an enzyme required for bacterial cell wall formation but some E. coli produces a slightly different version of the enzyme so reproduction may be slowed but will not stop. The other aspect of our hypothesis that temperature affects growth was found to be true as demonstrated by the plates stored at higher temperatures exhibiting substantially more growth. Determining the exact nature...
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