Effects of Osmotic Stress and Temperature on Microbial Growth

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Effect of Osmotic Stress and Temperature on Microbial Growth
BIO 3400-002L – Microbiology Lab

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Effect of Osmotic Stress and Temperature on Microbial Growth
Luiz Felipe Isidoro

ABSTRACT

Evolution allowed primitive forms of life to develop proteins and enzymes that made it possible for life to evolve under environments with hostile conditions, such as high salt and heat. More specifically, some bacteria selected genes that code for peptides with stronger intermolecular forces, coping with extreme heat, or for compatible solutes, which accumulate to compensate osmotic stress. The present study utilizes multiple bacterial strains to assess their ability to overcome unfavorable conditions and promote growth. To achieve this goal,
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For the multiple assays, performed by the different groups in which the section was divided, the mean and the standard deviation were calculated. The results were used to construct a histogram illustrating the conditions that offered the best growth, if any at all, for the organisms investigated.

Effect of Temperature on Growth - Procedure A

E. coli, M. luteus, and B. stearothermophilus samples were aseptically inoculated into five separate TSA plates each. After all plates were properly sealed with parafilm, one culture of each organism was incubated at a specific temperature (4˚C, 25˚C, 35˚C, 55˚C, or 70˚C) for 48 hours. The recordings made thereafter concerned each organism at each temperature, in observance of either presence or absence of growth.

Effect of Osmotic Stress and Temperature on Microbial Growth
Effect of Temperature on Growth - Procedure B

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As another way of indentifying the effects of temperature on the growth of different organisms, identical tubes containing liquid cultures of S. aureus, P. aeruginosa, and B. subtilis were incubated at 4˚C, 25˚C, 35˚C, 55˚C, or 70˚C for 45 minutes, followed by five minutes of warming up or cooling down to room temperature. Each tube was then diluted to a factor of 10–2, 10–4, and 10–6 with sterile saline. Subsequently, 100µL of each dilution was spread plated onto fresh TSA plates, which were then incubated at 37˚C for 24 hours. The observations
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