This is the write up for my microbial growth experiment.
Expected Results:
To do a viable count a serial dilution was done using E. coli. The original broth containing E. coli was diluted 8 times. It was expected that as the broth was more diluted less cells would grow on each subsequent plate. To test cell density E. coli was inoculated in 4 tubes of TSB and kept at different temperatures, 27, 37, 45, and 55 degrees celsius. The most optimal temperature for E. coli growth was expected to be 37 degrees celsius, this is because E. coli are adapted to live within the digestive tracts of humans and humans maintain a constant body temperature of 37 degrees celsius. The way cell density was measured was with a spectrophotometer. It was expected that the E. coli being incubated at 37 degrees celsius would have the biggest change in cell density. Additionally it was expected that E. coli would have the lowest cell density at 55 degrees celsius, this is because it is too hot for the cells to live at this temperature.
Observed Results:
The10-1and 10-2dilution plates produced lawns and the colonies were too numerous to count (TNTC). The 10-3dilution plate had 62 colonies on it, giving a density of 6.2*105CFU/mL. The 10-4dilution plate had less than 30 colonies which is too few to count. The 10-5, 10-6, 10-7, and 10-8dilution plates had no colony growth. The cell density over time experiment yielded expected results. The E. coli had most increased cell density at 37 degrees celsius and the least increase in density at 55 degrees celsius. The k value (number of generations per time period) and g value (generation time) were calculated for E. coli at all 4 tested temperatures. At 27 degrees celsius the E. coli had a k value of 0.013 and a g value of 75. At 37 degrees celsius the E. coli had a k value of 0.02 and a g value of 48.825. At 45 degrees celsius the E. coli had a k value of 0.012 and a g value of 82.748. At 55 degrees celsius the E. coli had a k value of 0.001 and a g value of 763.85.
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