Yogurt: Bacteria you can eat

       Microbial diseases have been on the minds of scientists for the past 200 years. Until Robert Koch, studying them has been but a mystery to the many scientists on their tail. Bacteria are probably the most abundant life forms on earth, and come in various sizes, shapes, characteristics and natures. Bacteria as pathogens can cause harmful and sometimes fatal sicknesses, such as scarlet fever, tuberculosis, and brucellosis, but many forms are extremely beneficial to health. Bacteria divide very rapidly and grow their colony size quickly to a visible level. The shapes of the colonies under a microscope can include circular, irregular, or branching. Using enzymes, or large proteins that quicken reactions by lowering activation energy, bacteria break down sugars chemically into other molecules. This process is called fermentation, and is their main food source. Specifically, Yogurt forming bacteria break down lactose to pyruvic acid, then to lactic acid , which lowers the pH of the milk. Lower pH levels allow the milk's proteins to curdle and become denaturized to give it the more solid texture we call yogurt. Like other beneficial Bacteria, yogurt helps break down organic waste material the body digests when it consumes food. Other types, like Intestinal bacteria, synthesize nutrients and break down indigestible material.Bacteria are very important in maintaining a healthy lifestyle, not that we can do anything about the billions that live within us.
       Specifically, yogurt is made by fermenting milk which contains specific strains of bacteria, all under controlled temperatures. The Bacteria feed on the natural milk sugars, passing on lactic acid as a waste product, lowering milk's pH levels. This increased acidity leads to entanglement, or denaturation, of milk's most common protein, casein. This gives yogurt its texture. In our lab, we will be using Koch's postulates to grow and test our yogurt bacteria, as well as ampicillin. Koch's postulates include first, describe the symptoms shown. Second, isolating the pathogen and establish a pure culture, then infect a healthy species to identify if the same symptoms occur. Finally, be sure that the pathogen is the same as the first.
       Our lab will be starting from Koch's third step, since we already know the bacteria causes yogurtness. This basic procedure will summarize how bacteria is used in some common foods we eat today. It will also explain the nature of  some common bacteria.

       My prediction is that, without any error or improper technique, the yogurt bacteria will create a well established yogurt texture in the milk. When working will E. coli, I will have to be very important in using sterile technique because it can be dangerous. I predict the nature of the E. coli will act much differently then the Yogurt bacteria visibly and what the actual bacteria consumes and produces.
       A summarization of the Procedure starts with explaining the key steps of the lab. After all of the test tubes were labeled, we have to make sure we not only stir well the different bacteria into the milk, but that we put the right bacteria into the right test tube. Proceeding the contamination of the bacteria to the milk, we have to place the test tubes into the incubator for  the correct environment for growth of the bacteria types.
       When we mixed the bacteria into the milk, there was no immediate effect, unlike a chemical reaction. As for the results the following day, here is the list. Test Tube 1, the positive control of just milk, smelled like sour milk, and had the same texture as before, liquid. Test Tube 2, the negative control or the yogurt in milk, transformed into a yogurt texture at the bottom half of the tube, and it smelled like regular milk. Test Tube 3, the yogurt + ampicillin, had the same results as Test Tube 1, same smell and texture. The E. Coli in Test Tube 4, had the same results, with a slight alteration in the smell. It didn't smell sour. As for color and pH, the milk, yogurt+ampicillin, and the E. Coli test tubes all were off-white with a pH of around 6-7. The yogurt had a more solid color and a lower pH of about 4.5.
       The reason the yogurt test tube was more solidified, and a more white color was because the bacteria of yogurt fed on the milk sugar, casein overnight and broke down the proteins, causing them to denature and spread apart (curdle). The ampicillin nuetrilized the yogurt bacteria, the E. coli bacteria has its own nature and doesn't feed on milk sugar, and the regular milk just maintained its color texture and pH. The reason the pH drops for the yogurt is because the bacteria can only properly ferment under those conditions, so the bacteria lower the level.
       The possible sources of error could have resulted from many things. These could include mixing the wrong bacteria into the right test tube, not labeling them in a color we would remember so we could find it in the incubator the following day, or mixing up the litmus paper when we took the pH's, which could have confused our results.