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The population of a bacterium will grow successfully in a particular pattern known as ‘logarithmic growth’ if the location is appropriate and the proper nutrients are present. The bacteria numbers will increase and most likely continue to double in this area over time with optimal conditions. Optimal conditions meaning that there are no dangers or limiting factors, to inhibit growth in this area, such as disease, predators, competition or lack of food. At first the bacteria should reproduce slowly, this is known as the lag phase but then over time it should increase more rapidly throughout what is called the log phase. This predictable pattern of growth can be called the organism’s biotic potation. Procedure

During this exercise the population growth of the bacteria Escherichia coli (E.coli) will be measured. If the conditions are right, the E.coli population will grow more rapidly the longer it stays in that area. Turbidity, meaning cloudiness, will be how the tubes are measured to give the results of bacterial growth. The more turbid the broth the more bacteria count the tube will contain. For this particular exercise, a broth has been prepared and separated into six test tubes labeled accordingly. The first test tube is labeled 0 as a control. This tube is a new broth that has not yet become turbid. The next tube is labeled 4hrs, meaning there has been a 4 hour growth period followed then by tubes marked at 8hrs, 12hrs, 24hrs and 48hrs, to represent the period of growth time allowed per tube. These tubes are covered, stirred and placed into a tray to wait further testing in the spectrometer.

As the E.coli reproduce, the broth should become more turbid and should then show an increased level of bacteria. Each tube will be wiped clean of all blemishes and placed into the spectrometer, set to 600nm. After each tube is tested the spectrometer is then reset to 0 using the control sample. Keeping each tube wiped free of any fingerprints and...
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