Koch's in the Kitchen: Yogurt postulates

Introduction

In the 1800s many scientists knew that bacteria existed, but they could not prove that the bacteria were the cause of the many appearing diseases and discomforts.  A scientist named Robert Koch developed 4 postulates that described how these new bacteria behaved.

1. The microorganism must be found in all organisms suffering from the disease, but not in healthy organisms.
2. The microorganism must be isolated from a diseased organism and grow in pure culture.
3. The cultured microorganism should cause disease when introduced into a healthy organism.
4. The microorganism must be again isolated from the inoculated, diseased experimental host and identified as identical to the original specific causative agent.

Many people think of disease when they hear the word Bacteria, but in fact, only a small percentage of the bacteria in the world are harmful.  This means that there are billions upon billions of different types of bacteria in the whole world.  Bacteria actually have their own domain, just like Eukarya and Archaea.  Bacteria are single celled microorganisms that actually play a giant role on our planet because they can do everything.  There are so many different types of bacteria that have different jobs just like people.  There are 3 main shapes of Bacteria, coccus (spherical), bacillus (rod-shaped), and spirillum (spiral).  Bacteria reproduce by binary fission, or copying itself and then splitting.   Bacteria also require food, just like any other living organism.  Bacteria are the ones responsible for eating sugars and then breaking them down into enzymes.


The purpose of this lab is to both demonstrate how not all bacteria is bad, case and point: yogurt.  And to reveal how little tiny single-celled microorganisms can create something so unique with very little material.  Because this technique for creating yogurt is so simple, yet so effective, large companies can utilize this and make yogurt for a cheap price and sell the person the container.  This may teach some people that it is much more cost effective to make their own yogurt with whatever fruits or flavors they desire.

When creating yogurt it is very important to label all important LAB materials, i.e. test tubes, petri dishes,    

etc.   Also it is important that all of the measurements are as accurate as possible.

Procedure

1. Fill 4 test tubes with milk.
2. Label each as follows, Negative Control (Milk), Positive Control (Milk), Positive Control + Ampicillin, E. Coli.
3. For the Negative Control, just leave as is.  For Positive Control, insert yogurt with plastic dowel and stir.  For Ampicillin, use a scientific dropper to insert the Ampicillin.  For E. Coli, scrape the cultures and drop it into the milk.
4.  Stir all of the tubes in a vortex stirrer.
5. Place all tubes into an incubating container of water at 37 degrees C.
6. Wait 24 hours and view results

Discussion 

After removing the tubes from the body temperature water, I observed each tube carefully to recognize which ones had created yogurt, and which had not.  From my results, the positive control did yield yogurt and so did the test tube with the Ampicillin.   The E. Coli and the Negative control though just stayed the same as they were before the incubator.  During the experiment I found that putting less yogurt on the plastic swab allowed me to insert it into the milk tube easier.