The spectrophotometer analysis of Escherichia coli growth during heat application
The purpose of this experiment is to determine the rate of Escherichia coli (E. coli) growth over 100 minutes in a liquid growth medium (control), and to determine the rate of E. coli growth over 100 minutes in a heated liquid growth medium. The prediction is that the control E. coli culture will grow at a faster rate exponentially over 100 minutes than the experimental bacteria culture. Consequently due to heat application, the experimental bacteria will not grow over the 100 minutes, and will either move into G0 of its cell cycle or will produce descending results as cell death occurs.
The null hypothesis for this experiment is that the experimental E. coli will not grow when heat is applied, unlike the control E. coli that will grow exponentially without an added environmental agent. The alternative hypothesis for this experiment is that the experimental E. coli and the control E. coli will have an exponential growth rate. Methods To prepare the control and experimental formulas, 20 mL of LB growth media and 20mL of E. …show more content…
coli are added to two separate test tubes. The control tube is placed into a rotating incubator, and the experimental tube is placed into a hot water bath between 70-80 degrees Celsius. To maintain this temperature, add hot water frequently to the bath. Next, add 2 mL of the control formula into a cuvette, and place into a spectrophotometer (after it has been zeroed at a wave length of 660 nm). Record the optical density reading on the spectrophotometer, and repeat for the experimental solution. This reading should be recorded as time 0. Be sure to measure the optical density for the experimental E. coli at 0 minutes before the tube is placed in the hot water bath. Wait 20 minutes, and measure the optical density for the two tubes again. Continue this process every 20 minutes for 100 minutes.
Results
After analyzing the growth of bacteria with and without heat application, my laboratory group and I determined that heat application slowed down E. coli growth over 100 minutes. Table 1 outlines the data gathered during the experiment. Note the growth of the control bacteria verses the growth of the experimental bacteria. The control bacteria acquired an optical density (OD) from 0.02 nm to 0.109 nm, whilst the experimental bacteria that were placed into a hot water bath stayed between the OD of 0.01-0.019 nm. Figure 1 illustrates the growth of the control E. coli within the growth medium during each of the 6 time intervals. The bacteria grew exponentially between 40 and 100 minutes. Between 20 and 40 minutes, the growth of the bacteria seemed to have plateaued, which could be due to a procedural error that will be discussed in the Discussion portion of this report. The R-squared statistic measuring the variation of the grey data line shows that the data collected has a limited variance around its mean OD, 0.0566 nm. Figure 2 describes the results of the experimental bacteria’s OD verses the 100 minutes of time in which the OD was calculated on the spectrophotometer. This graph is very obscure due to the data fluctuation that was gathered. The 0 minute calculation is left out due to forgetting to document the data before allowing the experimental bacteria tube to rest in the hot water bath. Between 20 and 40 minutes, the bacteria did exactly what we hypothesized, its growth rate decreased. However, between 40 and 80 minutes, the spectrophotometer recorded exponential bacterial growth until 80 minutes when there appeared to be another growth decline. The R-squared statistic for this graph shows little to none variation around a mean OD of 0.0164 nm. Overall, the environmental agent of heat did not completely halt bacterial growth over 100 minutes; therefore, we failed to reject our null hypothesis. Discussion/Conclusion When cells grow they go through the stages of the cell cycle continuously at a fixed rate until the nutrient supplies are depleted (Cell Biology Lab directions). The purpose of this experiment is to calculate the rate of cell growth by using a spectrophotometer to emit light through a bacterial solution. The control bacteria showed exponential growth over 100 minutes as indicated in Figure 1, and this growth indicates that
The purpose of this experiment is to determine the rate of Escherichia coli (E. coli) growth over 100 minutes in a liquid growth medium (control), and to determine the rate of E. coli growth over 100 minutes in a heated liquid growth medium. The prediction is that the control E. coli culture will grow at a faster rate exponentially over 100 minutes than the experimental bacteria culture. Consequently due to heat application, the experimental bacteria will not grow over the 100 minutes, and will either move into G0 of its cell cycle or will produce descending results as cell death occurs.
The null hypothesis for this experiment is that the experimental E. coli will not grow when heat is applied, unlike the control E. coli that will grow exponentially without an added environmental agent. The alternative hypothesis for this experiment is that the experimental E. coli and the control E. coli will have an exponential growth rate. Methods To prepare the control and experimental formulas, 20 mL of LB growth media and 20mL of E. …show more content…
coli are added to two separate test tubes. The control tube is placed into a rotating incubator, and the experimental tube is placed into a hot water bath between 70-80 degrees Celsius. To maintain this temperature, add hot water frequently to the bath. Next, add 2 mL of the control formula into a cuvette, and place into a spectrophotometer (after it has been zeroed at a wave length of 660 nm). Record the optical density reading on the spectrophotometer, and repeat for the experimental solution. This reading should be recorded as time 0. Be sure to measure the optical density for the experimental E. coli at 0 minutes before the tube is placed in the hot water bath. Wait 20 minutes, and measure the optical density for the two tubes again. Continue this process every 20 minutes for 100 minutes.
Results
After analyzing the growth of bacteria with and without heat application, my laboratory group and I determined that heat application slowed down E. coli growth over 100 minutes. Table 1 outlines the data gathered during the experiment. Note the growth of the control bacteria verses the growth of the experimental bacteria. The control bacteria acquired an optical density (OD) from 0.02 nm to 0.109 nm, whilst the experimental bacteria that were placed into a hot water bath stayed between the OD of 0.01-0.019 nm. Figure 1 illustrates the growth of the control E. coli within the growth medium during each of the 6 time intervals. The bacteria grew exponentially between 40 and 100 minutes. Between 20 and 40 minutes, the growth of the bacteria seemed to have plateaued, which could be due to a procedural error that will be discussed in the Discussion portion of this report. The R-squared statistic measuring the variation of the grey data line shows that the data collected has a limited variance around its mean OD, 0.0566 nm. Figure 2 describes the results of the experimental bacteria’s OD verses the 100 minutes of time in which the OD was calculated on the spectrophotometer. This graph is very obscure due to the data fluctuation that was gathered. The 0 minute calculation is left out due to forgetting to document the data before allowing the experimental bacteria tube to rest in the hot water bath. Between 20 and 40 minutes, the bacteria did exactly what we hypothesized, its growth rate decreased. However, between 40 and 80 minutes, the spectrophotometer recorded exponential bacterial growth until 80 minutes when there appeared to be another growth decline. The R-squared statistic for this graph shows little to none variation around a mean OD of 0.0164 nm. Overall, the environmental agent of heat did not completely halt bacterial growth over 100 minutes; therefore, we failed to reject our null hypothesis. Discussion/Conclusion When cells grow they go through the stages of the cell cycle continuously at a fixed rate until the nutrient supplies are depleted (Cell Biology Lab directions). The purpose of this experiment is to calculate the rate of cell growth by using a spectrophotometer to emit light through a bacterial solution. The control bacteria showed exponential growth over 100 minutes as indicated in Figure 1, and this growth indicates that