Payal Patel Lab Communication 2 Section 16Group 4 Which carbon source promotes the most bacterial growthIntroductionThe Krebs Cycle is how E. coli bacteria processes the carbon sources it obtains. It is a part of aerobic respiration. The goal at the end of the cycle is to produce ATP which is used for energy by the cell. The beginning processes of the Krebs Cycle uses glucose which is further broken down into other carbon sources. The other carbon sources further through the cycle can also be acquired by the cell to be used to process into ATP. (Schussler, Hudson, Rowe, Lemieux, Naswa 2012)After reading the article and relating it back to lecture, it was observed that glucose was more versatile and was the very beginning product that could be used in the Krebs Cycle. From the background information, we hypothesized that glucose would have more bacterial growth than glycerol because it can be broken down into more usable forms. Wepredicted that glucose would be more efficient in causing growth than glycerol. We think this will be the result because glucose is involved in the very beginning of the Krebs Cycle, and this would be efficient because it can be broken down and adjusted to the current needs of the bacteria. MethodsIn our experiment, our controls were our blanks: one with glycerol and another with no carbon source. The variable manipulated, the independent variable in other words, was the carbon source that was used. Two carbon sources were used under the same conditions: glycerol and glucose. The independent variable caused our amount of absorbance or rate of optical density to vary, and this is our dependent variable. In this experiment, the growth of bacteria was tested, which was measured by optical density with a spectrophotometer. For the glucose, there were no replicates. When testing glycerol, there were two replicates for every time interval for glycerol and the no carbon blank. To set up the experiment, first blanks were made by putting 4 mL of our no carbon source, glycerol, and glucose into their respective cuvettes. Then, e. coli was added to theliquid cultures: 2 mL to M9 + glucose, 2 mL to M9 NO C, 5 mL to M9 + glycerol, and 5 mL to M9 NO C.00.020.040.060.080.10.120.140.06 0.06 0.07 0.1 0.12GlycerolTime (min)Optical Density00.020.040.060.080.10.120.140.160.180.20.07 0.11 0.15 0.18GlucoseTime (min)Growth (optical density)00.020.040.060.080.10.120.140.160.14 0.07 0.06 0.06 0.04ControlTime (min)Growth (optical density)DiscussionBased on our results, the hypothesis was supported that glucose would be a better carbon source than glycerol because it could be broken down into many useable forms. The glucose cultures had significantly more growth than the glycerol source. It related the glucose being a better carbon source back to the fact it can be used in the early stages of the Krebs cycle to be broken down into other forms of metabolism. If we were to do this experiment again, more carbon sources would be used to compare to glucose, and have groups that were under different conditions to observe whether conditions the cultures are placed under also have an affect on which carbon source is more efficient for growth of the E. coli. References CitedSchussler, Elisabeth, Jan Hudson, Erica Rowe, Monique Lemieux, and Sudhir Naswa. Biology 140 Lab Manual. Knoxville, TN: University of Tennessee-Knoxville, 2012. 17-22. Print.Heiden, Matthew, Lewis Cantley, and Craig Thompson. "Understanding the Warburg Affect: The Metabolic Requirements of Cell Proliferation." Science 22 May 2009:1029-32. Print.Whiteley, Marvin, Kelli Palmer, and Stacie Brown. "Revisiting the Host as a Growth Medium." Nature Review Sept. 2008: 657-64.