The Effect of Heat and Growth on the Survival of Bacteria

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Aims
The purpose of the two experiments was to determine the fundamental effects that temperature has on the growth and survival of bacteria. During the first experiment five different bacterial broth cultures of Escherichia coli, Pseudomonas fluorescens, Enterococcus faecalis, Bacillus subtilis and Bacillus stearothermophilus were individually incubated at temperatures of 5, 25, 37, 45 and 55°C for one week in an aim to distinguish the effect temperature has on growth and survival of the five different species. After one week they were observed for distinguishable changes by the turbidity showing an indication of bacterial growth, or the clarity an indication of no survival. The second part of the experiment was to examine the effect temperature had on the survival ability of the five bacteria mentioned above. One of the five bacterial species were allocated per work bench for individuals to create broth culture with and expose to temperatures of 40, 60, 80 and 100°C for 2, 5, 30 and 90 minutes. As the same in experiment one, these cultures were then left for a week to incubate, then upon completion they were observed for distinguishable changes, such as the turbidity, clarity and the formation of endospores to show the bacteria’s survivability at particular temperatures. Information was then collated from other work benches to show the results from all five species. Results

Table 1. Table of results showing the effect temperature has on the growth and survival of bacteria. Temperature | 5°C| 25°C| 37°C| 45°C| 55°C|
Organism| | | | | |
Escherichia coli| 0| 2| 3| 3| 1|
Pseudomonasfluorescens| 2| 3| 1| 0| 0|
Enterococcusfaecalis| 0| 1| 2| 1| 0|
Bacillussubtilis| 0| 1| 2| 2| 3|
Bacillus stearothermophilus| 0| 0| 0| 2| 3|
0: No growth 1:Light growth 2:Medium growth 3:Heavy growth The table above shows the level of growth for each species of bacteria at various temperatures. The example of Escherichia coli showed no growth at 5°C whilst heavy growth occurred at 37°C and 45°C.

Table 2. Table of results showing the survival ability of bacteria at increasing temperatures for varying time periods. Temperature | 40°C| 60°C| 80°C| 100°C|
Time (minutes)| 2| 5| 30| 90| 2| 5| 30| 90| 2| 5| 30| 90| 2| 5| 30| 90| Bench| Organism| |
A| Escherichia coli| +| +| +| +| +| +| -| -| +| -| +| -| -| -| -| +| B| Pseudomonasfluorescens| +| +| +| +| +| +| +| +| -| -| -| -| -| -| -| -| C| Enterococcusfaecalis| +| +| +| +| +| +| +| +| -| -| +| -| -| +| -| -| D| Bacillussubtilis| +| +| +| +| +| +| +| +| +| +| +| +| +| +| -| error| E| Bacillus stearothermophilus| +| +| +| +| +| +| +| +| +| +| +| +| +| +| +| +| F| Escherichia coli| +| +| +| +| +| +| +| +| +| +| -| +| -| -| -| -| G| Pseudomonasfluorescens| +| +| +| +| +| +| -| -| -| +| +| +| -| +| -| +| X| Bacillussubtilis| +| +| +| +| +| +| +| +| +| +| +| +| +| +| +| +| Y| Bacillus stearothermophilus| +| +| +| +| +| +| +| +| +| +| +| +| +| +| +| +| Z| Enterococcusfaecalis| +| +| +| +| +| +| +| +| -| -| +| +| -| -| -| -| +: Presence of survival - :Absence of survival

The table above shows the presence or absence of each of the species of bacteria at increasing time periods for varying time periods. The example from bench B ‘s species Pseudomonas fluorescens clearly shows a survival ability at 40 and 60°C for all time periods of 2,5 30 and 90 minutes and no survival at 80 and 100°C. Discussion

Temperature is one of the most important factors affecting the survival and growth of bacteria. The temperature of the surrounding environment has an immediate impact on the bacterial cell. In comparison with that of multi-cellular organisms that have a more complex organisation that enables then to cope better with fluctuations of...
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