Question

Explain in a paragraph how to do kochs yogurtness lab in such a way that anyone could repeat the expirment

Answer 1

In 1884, Koch set forth specific criteria known as Koch’s postulates, which would establish disease etiology. Robert Koch showed that a specific microbe was responsible for a specific disease. In 1887, the germ theory of disease was being tested in Koch’s laboratory.

Koch's postulates:

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 grown 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.

Studying koch’s postulates with yougurt:

The experiment demonstrates a gerneal cause and effect of microorganisms. The “disease”, in this case is yogurt. Skim milk is the heathy, uninoculated state. The texture, odor and quality of the yogurt produced are the symptoms. Yogurt production requires two infecting bacteria, each with similar effects. The steps of the experiment are –

1. Isolate and identify bacteria from yogurt,
2. Re-inoculate skim milk with the bacteria you isolate and
3. Prepare edible yogurt of different qualities

Bacteria associated with yogurt production are Lactobacillus bulgaricus and Streptococcus thermophilus. On LSD (lactobacilli-streptococci differential) medium, both colonies are colored red. They both are fermenting microbes.

Streptococcus thermophilus are cocci and Gram+ve cells. On LSD media, which forms small (0.5 mm), round regular colonies.

Lactobacillus bulgaricus are Gram +ve rods, forms short chains. On LSD media, which forms Large (1-2 mm), irregular colonies.