1.1.3.2: Koch's Postulates and Pure Culture
Section Learning Objectives
- Explain Robert Koch’s postulates
Related Chapter Learning Outcomes:
- Explain germ theory of disease and the link to Koch’s Postulates
- Apply Koch’s Postulates
Robert Koch was born in Clausthal in the Harz Mountains, then part of the Kingdom of Hanover, as the son of a mining official. He studied medicine at the University of Göttingen and graduated in 1866. He then served in the Franco-Prussian War and later became district medical officer in Wollstein (Wolsztyn), Prussian Poland. Working with very limited resources, he became one of the founders of bacteriology, the other major figure being Louis Pasteur.
After Casimir Davaine demonstrated the direct transmission of the anthrax bacillus between cows, Koch studied anthrax more closely. He invented methods to purify the bacillus from blood samples and grow pure cultures (cultures in which only one type of organism is growing). He found that, while it could not survive outside a host for long, anthrax built persisting endospores that could last a long time. These endospores, embedded in soil, were the cause of unexplained “spontaneous” outbreaks of anthrax. Koch published his findings in 1876 and was rewarded with a job at the Imperial Health Office in Berlin in 1880. In 1881, he urged for the sterilization of surgical instruments using heat.
Probably as important as his work on tuberculosis, for which he was awarded a Nobel Prize in 1905, are Koch’s postulates. These postulates stated that to establish that an organism is the cause of a disease:
- it must be found in all cases of the disease examine and must be absent from healthy organisms
- the suspected pathogen must be prepared and maintained in a pure culture
- the cultured organism must be capable of producing the original infection, even after several generations in culture
- the same organism must be retrievable from an inoculated animal and cultured again.
Although we now know that Koch's postulates are not applicable for every infectious disease, using his methods Koch’s pupils found the organisms responsible for diphtheria, typhoid, pneumonia, gonorrhoea, cerebrospinal meningitis, leprosy, bubonic plague, tetanus, and syphilis.
Perhaps the key method Koch developed was the ability to isolate pure cultures. Developing pure culture techniques is crucial to the observation of the specimen in question. The most common method to isolate individual microbes and produce a pure culture is to prepare a streak plate. The streak plate method is a way to physically separate the microbial population and is done by spreading the inoculate back and forth with an inoculating loop over the solid agar plate. Upon incubation, colonies will arise. Because each colony begins with a single cell, that organism will have been isolated from the biomass.
Key Points
- Koch’s research and methods helped link the causal nature of microbes to certain diseases, such as anthrax.
- As developed by Koch, pure cultures allow the pure isolation of a microbe, which is vital in understanding how an individual microbe may contribute to a disease.
- According to Koch’s postulates, for an organism to be the cause of a disease, it must be found in all cases of the disease and must be absent from healthy organisms, as well as maintained in pure culture capable of producing the original infection.
Key Terms
- anthrax : An infectious bacterial disease of herbivores than can also occur in humans through contact with infected animals, tissue from infected animals, or high concentrations of anthrax spores.
- metazoa : All those multicellular animals, of the subkingdom Metazoa, that have differentiated tissue.
- tuberculosis : An infectious disease of humans and animals caused by a species of mycobacterium mainly infecting the lungs where it causes tubercles characterized by the expectoration of mucus and sputum, fever, weight loss, and chest pain, and transmitted through inhalation or ingestion of bacteria.
LICENSES AND ATTRIBUTIONS
CC LICENSED CONTENT, SPECIFIC ATTRIBUTION
- OpenStax College, Bacterial Diseases in Humans. January 17, 2014. Provided by : OpenStax CNX. Located at : http://cnx.org/contents/0a866b1c-8f44-489a-ae8c-6e100ca0ee55@10 . License : CC BY: Attribution
- Microorganism. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Microorganism. License : CC BY-SA: Attribution-ShareAlike
- Microbe. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Microbe. License : CC BY-SA: Attribution-ShareAlike
- Microorganism. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Microorganism. License : CC BY-SA: Attribution-ShareAlike
- Microorganism. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Microorganism. License : CC BY-SA: Attribution-ShareAlike
- symbiote. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/symbiote. License : CC BY-SA: Attribution-ShareAlike
- pathogenic. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/pathogenic. License : CC BY-SA: Attribution-ShareAlike
- ecosystem. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/ecosystem. License : CC BY-SA: Attribution-ShareAlike
- Provided by : Wikimedia. Located at : upload.wikimedia.org/Wikipedia/commons/7/75/Hassall_-_Microbes_in_Thames_at_Brentford_and_Hungerford.jpg. License : Public Domain: No Known Copyright
- Ferdinand Cohn. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Ferdinand_Cohn. License : CC BY-SA: Attribution-ShareAlike
- Microbes. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Microbes%23Classification_and_structure. License : CC BY-SA: Attribution-ShareAlike
- Ferdinand Cohn. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Ferdinand_Cohn. License : CC BY-SA: Attribution-ShareAlike
- Microbes. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Microbes%23Classification_and_structure. License : CC BY-SA: Attribution-ShareAlike
- classification. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/classification. License : CC BY-SA: Attribution-ShareAlike
- Provided by : Wikimedia. Located at : upload.wikimedia.org/Wikipedia/commons/7/75/Hassall_-_Microbes_in_Thames_at_Brentford_and_Hungerford.jpg. License : Public Domain: No Known Copyright
- Antoni van Leeuwenhoek (by Jan Verkolje, 1686). Provided by : Wikimedia. Located at : commons.wikimedia.org/wiki/File:Antoni_van_Leeuwenhoek_(by_Jan_Verkolje,_1686).jpg. License : Public Domain: No Known Copyright
- Louis Pasteur. Provided by : Wikimedia. Located at : commons.wikimedia.org/wiki/File:Louis_Pasteur.jpg%23file. License : Public Domain: No Known Copyright
- Spontaneous generation. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Spontaneous_generation. License : CC BY-SA: Attribution-ShareAlike
- Louis Pasteur. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Louis_Pasteur. License : CC BY-SA: Attribution-ShareAlike
- Spontaneous generation. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Spontaneous_generation. License : CC BY-SA: Attribution-ShareAlike
- abiogenesis. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/abiogenesis. License : CC BY-SA: Attribution-ShareAlike
- germ theory. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/germ%20theory. License : CC BY-SA: Attribution-ShareAlike
- Provided by : Wikimedia. Located at : upload.wikimedia.org/Wikipedia/commons/7/75/Hassall_-_Microbes_in_Thames_at_Brentford_and_Hungerford.jpg. License : Public Domain: No Known Copyright
- Antoni van Leeuwenhoek (by Jan Verkolje, 1686). Provided by : Wikimedia. Located at : commons.wikimedia.org/wiki/File:Antoni_van_Leeuwenhoek_(by_Jan_Verkolje,_1686).jpg. License : Public Domain: No Known Copyright
- Louis Pasteur. Provided by : Wikimedia. Located at : commons.wikimedia.org/wiki/File:Louis_Pasteur.jpg%23file. License : Public Domain: No Known Copyright
- Experiment Pasteur English. Provided by : Wikimedia. Located at : commons.wikimedia.org/wiki/File:Experiment_Pasteur_English.jpg. License : Public Domain: No Known Copyright
- Koch's postulates. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Koch's_postulates%23Koch.E2.80.99s_postulates_for_the_21st_century. License : CC BY-SA: Attribution-ShareAlike
- Microbiological culture. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Microbiological_culture%23Isolation_of_pure_cultures. License : CC BY-SA: Attribution-ShareAlike
- Robert Koch. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Robert_Koch. License : CC BY-SA: Attribution-ShareAlike
- Koch's postulates. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Koch's_postulates%23Koch.E2.80.99s_postulates_for_the_21st_century. License : CC BY-SA: Attribution-ShareAlike
- Anthrax. Provided by : Wikipedia. Located at : en.Wikipedia.org/wiki/Anthrax. License : CC BY-SA: Attribution-ShareAlike
- metazoa. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/metazoa. License : CC BY-SA: Attribution-ShareAlike
- anthrax. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/anthrax. License : CC BY-SA: Attribution-ShareAlike
- tuberculosis. Provided by : Wiktionary. Located at : en.wiktionary.org/wiki/tuberculosis. License : CC BY-SA: Attribution-ShareAlike
- Provided by : Wikimedia. Located at : upload.wikimedia.org/Wikipedia/commons/7/75/Hassall_-_Microbes_in_Thames_at_Brentford_and_Hungerford.jpg. License : Public Domain: No Known Copyright
- Antoni van Leeuwenhoek (by Jan Verkolje, 1686). Provided by : Wikimedia. Located at : commons.wikimedia.org/wiki/File:Antoni_van_Leeuwenhoek_(by_Jan_Verkolje,_1686).jpg. License : Public Domain: No Known Copyright
- Louis Pasteur. Provided by : Wikimedia. Located at : commons.wikimedia.org/wiki/File:Louis_Pasteur.jpg%23file. License : Public Domain: No Known Copyright
- Experiment Pasteur English. Provided by : Wikimedia. Located at : commons.wikimedia.org/wiki/File:Experiment_Pasteur_English.jpg. License : Public Domain: No Known Copyright
- Robert Koch. Provided by : Wikimedia. Located at : commons.wikimedia.org/wiki/File:Robert_Koch.jpg. License : Public Domain: No Known Copyright