Koch's Postulates

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Koch's Postulates


Koch created four guidelines to determine the causal agents of disease in humans, animals, and plants. Koch proved that a disease-causing agent could be transferred from one organism to another and create the same illness. Isolation of pure cultures and the introduction of the disease-causing agent to a healthy organism will transmit the disease and infect the inoculated organism. Koch's four guidelines by which one must follow to transmit a disease from an infected organism to a healthy one are as followed: 1. The specific organism should be shown to be present in all cases of animals suffering from a specific disease but should not be found in healthy animals.

2. The specific microorganism should be isolated from the diseased animal and grown in pure culture on artificial laboratory media.

3. This freshly isolated microorganism, when inoculated into a healthy laboratory animal, should cause the same disease seen in the original animal.

4. The microorganism should be reisolated in pure culture from the experimental infection.

In this exercise, Penicillium was utilized, a common, safe, mold. Certain species of Penicillium will spoil fruits, vegetables, grains, and grasses. Other species will ripen various chesses. Still, other species are used in the production of antibiotics. The species of Penicillium, italicum is provided for the lab because of its pronounced hyphae. Penicillium italicum, along with Penicillium digitatum attack citrus fruits post-harvest. In this experiment, the effect of Penicillium italicum on two types of citrus fruits and one non-citrus fruits were tested.

Materials & Methods

1. Pick several appropriate fruits.
2. Gently was fruit in cool, soapy water, using a scrub brush on the citrus fruits, then rinse thoroughly with cool running tap water. 3. Place citrus in a beaker and cover with a 10% bleach solution. Let soak for 10 minutes. 4. Rinse thoroughly with cool running tap...
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