Temperature Effects on the Growth of Microorganisms

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Temperature effects on the growth of microorganisms


The purpose of this experiment was to determine the effects that temperature has on three different organisms. Temperature is one of the most important environmental factors affecting growth and survival of microorganisms². The three organisms used where Escherichia coli, Pseudomonas fluorescens, and Bacillus stearothermophilis. Most bacteria grow within a particular temperature range. The minimum growth temperature is the lowest temperature at which a bacterium can still grow, while the maximum growth temperature is the highest temperature at which a particular bacterium can still grow. The optimum growth temperature is the temperature at which the bacterium can grow at the highest rate¹. The lab group hypothesized that B. stearothermophilis would only grow at 47° C. That E. coli would grow above 13° C but stop growing above 45° C and P. fluorescens would also grow between the temperatures of 13° C and 45° C. Upon completion of incubation, results were collected as growth or no growth for each temperature.

Methods and Materials:

Figure 1a: agar plate Materials
6 nutrient agar plates
media grown overnight in Tryptic Soy Broth
E. coli
P. fluorescens
B. stearothermophilis
Inoculum loop Divide into 3 sections, Incubator for 4°, 15°, RT, 30°, 35°, and 47° label each and inoculate with all 3 organisms

Obtain six nutrient agar plates and divide each into three equal sections. (See figure 1a) Label each dish properly. Use aseptic technique³ and inoculate each dish with three different organisms. The...