Koch's Postulates

So far this semester, I have learned that Robert Koch was instrumental in proving that bacteria cause disease.

This German physician was successful in isolating Bacillus anthracis in 1877, Mycobacterium tuberculosis (MBT) in 1882 and Vibrio cholera in 1883.
He was awarded a Nobel Prize in 1905 for his isolation of the Mycobacterium tuerculosis and other tuberculosis findings.

Becasue Koch proved that bacteria cause disease we were able to create drugs to cure disease by attacking the pathogenic bacteria that infect our bodies.

Koch postulated that:
  1. Microorganisms that cause disease can be isolated from diseased tissue.
  2. This isolated bacteria can be grown as a pure culture and identified using various characteristic tests and observations.
  3. If this pure culture of bcateria was injected into a healthy organism, the same disease symptoms would appear.
  4. The same bacteria can be isolated from the now diseased organism.

In my Microbiology lab, we started an experiment to see if we could prove Koch's postulates.
The plants that we used had a disease that caused red-purple swellings/tumors on their stems. These tumors had white, hair-like protrusions. After observing the disease conditions the tumor was removed and ground so we could isolate the bacteria within.

Last week we isolated bacteria from this tumor in the plant, and we grew a pure culture of this bacteria. I used a colony from this pure culture to infect a healthy plant. This actually turned out to be harder than I expected as the first healthy plant I tried to infect actually broke... ooops! The toothpick that I was trying to use to make a hole in the stem actually was too big and severed the stem most of the way through! Fortunately I was able to get another healthy plant. This time I used a smaller toothpick and punctured the stem. Then I used that same toothpick to pick up some cells from a colony and use these cells to plug the hole I just formed.

Next week in lab, we'll see whether the same type of tumor forms in this healthy plant.