Science / Temperature Effects On The Growth Of Microorganisms

Temperature Effects On The Growth Of Microorganisms

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Autor:  anton  08 November 2010
Tags:  Temperature,  Effects,  Growth,  Microorganisms
Words: 1162   |   Pages: 5
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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 microorganismsІ. 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 rate№. 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


6 nutrient agar plates

media grown overnight in Tryptic Soy Broth

E. coli

P. fluorescens

B. stearothermophi lis

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 techniqueі and inoculate each dish with three different organisms. The three organisms are E. coli, B. stearothermophilis, and P. fluorescens. Each plate containing three different organisms is incubated at six different temperatures; 4° C, 15° C, room temperature, 30° C, 35° C, and 47° C for 24 hours. The incubators are controlled by the instructors. The agar plates are placed in the appropriate incubator for the corresponding temperature. After 24 hours of incubation at different temperatures data was collected. Pictures where taken by the lab group and are seen in the results section. Visual data in the form of digital photographs were collected in regards to growth or no growth.


The resulting effects of temperature on the growth of several bacteria are seen in figure 1-6. E. coli did not grow at a temperature of 4° C, however the minimum temperature of growth was 15° C and the maximum temperature was 47° C. Therefore E. coli would be considered a mesophile with the optimal growth temperature around 35° C. A mesophile is an organism living in temperatures ranging from 15° C to 47° C. B. stearothermophilis did not start to grow until 47° C, therefore would be considered a thermophile. A thermophile is an organism that thrives in hot environments. The optimal temperature for a thermophile is around 65° C, and the minimal growth temperature starting at 40° C. The lab group was unable to determine maximum growth. The B. stearothermophilis was just starting to grow and had minimal growth at 47° C. P. fluorescens grew at temperatures 15° C through 30° C and is therefore also a mesophile. Around room temperature was the optimal growth temperature for P. fluorescens. Temperature preferences and growth or no growth for all organisms is shown in Table #1.


The results of this experiment determined that E. coli and P. fluorescens where both mesophiles. E. coli had an optimum growth temperature of 35° C and P. fluorescens’s optimum growth temperature was room temperature. A mesophile has a growth temperature range between 15° C and 47° C. B. stearothermophilis was determined to be a thermophile with minimal growth at 47° C. The lab group was unable to determine the optimum growth temperature of B. stearothermophilis, because the maximum growth temperature is extremely high and unable to be simulated in lab. However, the optimal growth temperature of a typical thermophile is 65° C І. The lab group’s hypothesis was supported by the data that was collected. The results of the data was placed into graphs and tables and evaluated to determine which category each organisms fits into. Upon completion of the experiment the data collected correlates with the correct environmental preference of the microbes being tested.

Other tests to determine environmental effects on microbial growth include; pH tests, sodium effects and oxygen effects. These tests will further characterize each organism’s growth parameters. All of these tests including temperature help to explain the distribution of microorganisms in nature and make it possible to devise methods to control or enhance microbial activities.І


1. Furlong, (2005), “Temperature Effects on Growth,” lab8 handout-Microbiology for Health Science, available at

2. Madigan, M., and Martinko, J.M. (2006), “Environmental Effects on Microbial Growth: Temperature,” Biology of Microorganisms, 11, 150-156.

3. Sherwood, L., and Hudson, B.K. (1997), “Explorations in Microbiology,” Montana State University, 1997.

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