Yogurt and bacteria for dummies

       In the 1800s people sickened and died for no apparent cause. Koch's postulates were invented by Robert Koch in order to prove that a certain microbe caused a certain disease. Bacteria are small microbes that are all around us. They are the the most successful form of life on the great planet Earth. Bacteria have no separate place for the nucleus like eukaryote do. Most bacteria are harmless and do not harm humans in any way. There are a small amount of bacteria that can harm you. There are also some bacteria that are actually good for humans and their digestive systems. These bacteria are called probiotics and can be found in yogurt and other foods. Bacteria that form yogurt are anaerobes and they use enzymes to break down milk sugar (lactose) into lactic acid.
      The purpose of this lab is to prove all of Koch's postulates especially postulate 3. Postulate 3 is: Inoculate healthy individual with pure culture of suspected pathogen. The oobjective of the lab is to use yogurt, ampicillin, and e.coli to prove this point. The technique we are using to prove postulate 3 is used all around the world in different ways to create yogurt from milk. Koch's postulates are also used in labs to isolate unknown pathogens.
       In the experiment we have 4 tubes of milk. We add ampicillin to the Yogurt + amp tube. Then we add yogurt to the yogurt + amp tube and another just milk tube. We are doing this to show that the pathogen is a bacteria because ampicillin kills bacteria so if nothing happens to that tube and the other tube becomes yogurt we know it was the bacteria. After all of this we then add e.coli to a tube of milk. We do this to show that introducing bacteria itself can cause the change to yogurt therefore isolating the pathogen.
       When we recieved our tubes back we came up with some expected and unexpected results. The negative tube that was filled with just milk had stayed in liquid for which was to be expected. The E.coli tube had also stayed in liquid form which had also been expected. The tube which had Yogurt + amp had changed into yogurt which wasn't supposed to happen. Also the tube that contained just milk with yogurt had stayed liquidy. I think this occured because of human error. I think that my group miss labeled the tubes with yogurt+amp and yogurt therefore switching them and explaing the unexpected results.

E.Coli

Yogurt

VIDEO:
http://www.youtube.com/watch?v=fKG-6jEwh_0