The effect of temperature on the growth of the bacteria Escherichia coli DH5α

DH5α is specific strain of E. coli that is a nonpathogenic bacterium belonging to the genus Escherichia. I used this type of bacteria to study comparative growth rates at different temperatures (28°C, 37°C, and 45°C) and for different times (24h, 48h, and 72h). I predicted that bacteria would grow best at 37°C compared to the other temperatures, because the mean temperature of many mammals is 37°C. Mammals often serve as a host to E. coli. To compare growth rates, I grew the bacteria in liquid nutrient broth cultures and on nutrient agar in Petri dishes. I used the spectrophotometer to measure the optical density of bacteria growth in the liquid media and counted colonies in the Petri dishes. The number of colonies on Petri dishes did not show a statistically significant difference among the three temperatures. However, in liquid media, the bacteria grew significantly better at 37°C for the three time periods (F = 0.06, d.f. = 2, P = 0.565), compared to the other temperatures, supporting my hypothesis.