The Effects of Various Factors on the Growth Rate of E. coli

The Effects of Various Factors on the Growth Rate of E. coli

Introduction:

There are times in our lives (as human beings) when people do not feel well. A doctor might diagnose them with a disease or an infection. There are also times when people do not feel clean. This could be a person's feeling after exercising, sweating, or maybe he/she had not taken a shower in a couple days. In any of the preceding scenarios, bacteria most likely played a major role in initiating a person's feeling of illness or squalor. "Sickness" can be caused from bacteria. Someone may be sick because they ate food contaminated with bacteria or they could have easily taken a sip from the cup of a friend and shared some sort of bacterial disease. Bacteria surrounds us everyday, every second. It is difficult for people to accept this fact because they want to believe they are clean, after they shower. In relative terms, a washed person is clean, but they are not free of bacteria. "Clean" is simply an image, because bacteria are covering all substances and objects that you use to be clean; toothbrushes, soap, and even toilet paper. We live in a world of bacteria, maybe even a world that evolved from bacteria.

These microscopic organisms reproduce quickly, sometimes even exponentially. In the experiment today, my class is observing and measuring data of how different factors can influence the rate at which bacteria grows. We will use Escherichia coli (E. coli) as our bacteria. It is a Gram-negative bacterium that resides in the intestines of humans (Laboratory Experiences, 34).

Before you can fully understand the experiment and it purpose, it is important to understand the phases bacteria go through when reproducing in various media. In general, a bacterial will go through four distinct phases; a lag phase, log phase, stationary phase, and a death phase. The lag phase shows how bacteria reproduce at a very slow rate at first. At this point, the cells are preparing for division. They are making sure to manufacture fats and proteins for the reproduction ahead. The second phase is the log (logarithmic or exponential) phase. The bacteria is now replicating rapidly and becoming so large in numbers that space is growing smaller, as is non-hazardous room and nutrient. Due to this rapid growth, the next step is the stationary phase. In this phase, about fift...

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... For the effects of aeration, we can say that E. coli doesn't necessarily need oxygen for growth.

Some errors in this experiment could have occurred at the spectrophotometers readings.

Students may have forgotten to re-zero the spec 20 before each new sample. Another source of error could be how temperature affects the bacteria. A student could have held a cuvette long enough to make the solution a little bit warmer, which could effect the growth curve for that sample.

For future research in this field, I would someday like to see if they could make a substance that would remove bacteria from skin. I could also see a substance that a human could digest to make the body resist all bacterial diseases. Although this seems crazy, bacteria can be limited by many factors. We live in the age of technology, and I believe that at this point, anything is possible.

References

Campbell, N.A., Reece, J.B., Mitchell, L.G. 1999. Biology. Menlo, CA: Addison

Wesley Longman, Inc.

Gregg, G., Hooke, A.M., McClure, J., Solomon, N.G. 2001. Laboratory Experiences for

Biological Concepts: Stucture, Function, Cellular, and Molecular Biology.

Oxford, OH: Miami University.