A Google Doodle for Robert Koch

Microbiology
STEM
Environmental and Science Education
Edward Hessler

Today's Google Doodle celebrates Robert Koch, a German physician and microbiologist who was awarded the 1905 Nobel Prize in Physiology or Medicine "for his investigations and discoveries in relation to tuberculosis."

You may remember his postulates from a first course in biology. 

1. The microorganism must be present in every case of the disease.
2. The microorganism must be isolated from a host organism with the disease and grown in pure culture.
3. Samples of the organism grown in pure culture muct cause the same disease when inoculated into a healthy animal in the laboratory.
4. The organism must be isolated from the inoculated animal and be identified as the same organism first isolaated from the orginally diseased host.

Koch recognized limitations of these postulates, e.g., some diseases to not meet all four requirements of the postulates, some disease causing organisms can be isolated from both sick and healthy organisms, and a third limitation, not discovered until well after Koch, are diseases caused by viruses.

New methods based in molecular biology, discussed at the Virology Blog, have made the original postulates even less applicable.  The entry linked at the Virology Blog discusses post-Koch details as well as includes a new list of Koch's postulates for the 21st century. There are seven.

Note added: And just what did Koch really do?  Before his meticulous work, wonderfully recounted in the Microbe Hunters, tuberculosis was thought to be inherited. Koch showed it was not inherited but caused by a microbe, Mycobacterium tuberculosis.

Koch with Pasteur are sometimes considered the "fathers" of bacteriology. There are other candidates as well. Whether two or more, an impressive lineage.