Robert Koch established a set of postulates to determine if a microorganism is the cause of a specific disease. The postulates require that (1) the pathogen must be found in all cases of the disease, (2) the pathogen can be isolated and grown in pure culture, (3) the pathogen from the pure culture must cause the disease when introduced into a healthy host, and (4) the pathogen must be re-isolated from the new host and found to be the same as the original pathogen. Koch's postulates provided a rigorous scientific framework for establishing causation between a microbe and a disease and advanced the field of microbiology. However, the postulates have limitations and do not apply to all disease situations

1. Koch Postulates
by
Protim Sinha

2. Robert Koch
• Robert Koch was a Physician and Microbiologist
born in 1843.
• Awarded Nobel prize for isolating the pathogen for
tuberculosis

3. Postulate I
A pathogen is associated
with a disease.

4. A pathogen is associated with
a disease.
• Leaf spots in Basella.

5. Scoop out
the reddish
spot and
prepare a
slide
Observe
under a
microscope
A pathogen is associated with a
disease.

6. Observation
Fungal Hyphae
Fungal Spore

7. Observation
Based on the Morphology, we
can conclude the fungi is
Alternaria Sp.
a common
pathogen that attack spinach

8. The pathogen can be isolated
from the diseased animal and
grown in pure culture in the
laboratory
Postulate II

9. The leaf spot is
cut with a sharp
blade into tiny
pieces
The leaf is placed
in an Agar dish to
let the pathogen
grow.
E X P E R I ME N T

10. Postulate II
Day 0 Day 7

11. The Pathogen causes same
disease when introduced
into fit susceptible host.
Postulate III

12. PostulateIII
Fresh leaf +
Spore Solution.
Wait for
few days
Leaf spots
appears

13. The same pathogen can be
cultured from the New
host
Postulate IV

14. Cultured

15. Merits of Koch
Postulates
1. It Established the cause of disease
2. It gave an idea about Isolation of pathogen

16. Limitations of Koch
Postulate
• Do not work for disease complexes.
• Is not applicable for Virus
• Is not applicable for humans on Ethical grounds.

17. Conclusion
1. A specific Pathogen is always associated with a given disease.
2. The microorganism can be isolated from the diseased Host and
grown in pure culture in the laboratory.
3. The cultured Pathogen will cause disease when transferred to a
healthy Host.
4. The same type of microorganism can be isolated from the newly
infected Host.

18. Thank You
Hi reader , this was a seminer that I had to give
infront of about 200 people. And was my first-time
infront of people, it was not so bad afterall.
The second Image of the plate ,the First image of
Leaf is not original.
The others are my original image. Thanks for
reading.