Microbial GrowthIn this laboratory, we measured the absorbance, at 15 minute intervals, of Escherichia coli in tryptic soy broth using a spectrophotometer. Using the optical density (OD) measurements provided by the spectrophotometer, we are then able to calculate the growth rate (k) and generation time (g) values ​​of the E. coli cultures. coli at different temperatures. OD readings were taken for cultures of E. coli incubated at 37°, 27°, 45° and 55°. at 15 minute intervals for 75 minutes. OD is a measure of the turbidity of the culture, as such it cannot differentiate between viable and dead cells. In part II of the laboratory, we performed serial dilution and plating of E. coli. coli, after incubation, we performed a viable count of plates containing between 30 and 300 colonies to determine the number of colony-forming units per ml. no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get the original essay For the growth experiment at different temperatures, we expect our data to indicate that the optimal growth temperature for E. coli is 37°C. Our hypothesis is based on the growth conditions of E. wild coli, E. coli bacteria are typically found in the intestines of humans and other animals, where the internal temperature is around 37°C. At temperatures above (45?) and below (27?) 37? we expect some growth, although it will likely be slowed as the bacteria will have to adapt to these temperatures. At 55? we don't expect any growth because this temperature is far too high for bacteria to survive. For the viable counting experiment, we would expect our spread plates from our dilution to show a decrease in colony counts for the most diluted culture. For serial dilution plates, dilutions from 1X10-1 to 1X10-4, the number of colonies was too numerous to count, the 1X10-5 dilution plate contained 59 colonies and the colonies from the 1X10-6 dilution plates at 1X10-8 were too few to count. For the 10-5 dilution, we calculated the number of colony forming units per ml to be 5.9 x 107 CFU/ml. This was calculated using a volume of 0.1 ml, a dilution factor of 105 and a colony count of 59. The OD values ​​for each 15 minute interval, for the growth experiment, are shown below. below in Figure 1. Using this data, we can calculate the k and g values ​​for each temperature tested. With a start time of 15 minutes (N0) and an end time of 75 minutes (N), the value of n can be calculated, which is necessary to determine k. The formula for k is k=n/t, where n=3.3*(log N - log N0) and t is the time interval in hours. The k values ​​(generations/hour) for 27?, 37?, 45? and 55 ?, respectively, are 0.85 generation/hour, 1.63 generation/hour, 1.69 generation/hour and 0.14 generation/hour, respectively. Using k, we calculated g (generation time) as g = 1/k. This gives us a generation time of 1.17 hours, 0.61 hours, 0.59 hours and 6.97 hours for each temperature respectively. Converting these values ​​to hours and minutes gives a generation time of 1 hour 10 minutes for 27 ?, 37 minutes for 37 ?, 35 minutes for 45 ? and 6 hours 58 minutes for 55 ?. We also plotted the absorbance versus time for each temperature, as shown in Figure 2 below. Our results for the growth experiment did not match.