Instructor Copy: Koch’s Postulates
Scientific Method, and Infection in Potatoes
in your textbook on page 579. On pages 1081-1082, you can read about
What Causes Stomach Ulcers?
Read page 1 and fill in the blanks at the bottom of the page.
Microorganisms that cause diseases are called
These pathogens can be isolated today, much in the same way as Robert Koch established
many years ago. In this lab, you will be the scientist responsible for testing a specific microbe
using Koch’s Postulates. It is important
to note that the microbe with which you will be working is not pathogenic to humans; it cannot make you sick. This microbe is a pathogen only to plants
It causes a plant disease called
As long ago as the 16th century, it was thought that something unseen could cause disease. Even in ancient times, it was recognized that diseases
. Individuals with leprosy were segregated from healthy people. In 1876,
was studying a disease of cattle called
and found convincing evidence that the
was caused by a bacterium that was named
In studying this disease, he
method for determining whether a microorganism actually causes a disease. This method is called Koch’s Postulates.
In 1876, Koch
observed that cows infected with a disease called anthrax had millions of bacteria in their blood. He
bacteria found in the blood of
the sick cow caused the disease.
To test his hypothesis, he
isolated bacteria from the host
(the organism harboring the microorganism) and
grew it in the laboratory
. He then
inoculated a healthy cow with these suspected bacteria that had been grown in the lab.
After some time the
new host showed signs of the disease.
isolated the bacteria found in his new host and then compared it with the original bacteria and identified them to be the same.
He concluded after
many trials that
specific bacteria did indeed cause the disease.
In 1990, when stomach ulcers, long accepted and treated as the result of
excess stomach acid
, were shown by Koch’s Postulates to be caused by the
Sadava, et al
, 579) Two scientists, Marshall and Warren, concluded that
antibiotic treatment eliminated the bacteria
and the inflammation in the host.
The experiment was repeated on
healthy volunteers and many patients with gastric ulcers were cured with
How would you show results for each of the postulates based on the following statement?
Stomach inflammation leading to ulcers is
infections in the stomach.
Sadava, et al,
1082) Marshall used himself as the test subject.