7.1.2

Question 1

Germ Theory

Answer 1

Spontaneous generation: Germs and other micro-organisms were discovered as early as the 17th century. Scientists believed that microbes were created from decaying matter (rotting food, waste). It led people to believe that diseases caused germs, rather then the other way.

Pasteur’s Germ Theory: germs caused disease and decay, not the other way round.

• Pasteur worked in the wine industry – recognised that wine sours over a period of time.
• He discovered that the sour wine had been contaminated by smaller microbial cells in addition to yeast cells (for fermentation). These small cells were bacteria that produce lactic acid rather than ethanol when underging anaerobic respiration, giving the wine a sour taste.

Question 2

Evidence of the germ theory

Answer 2

Nutrient broth was boiled in a swan neck flask to kill any existing microbes, and left to cool for several days. Broth in the normal flask/broken swan neck showed microbial growth.

This proved that germs are present in the environment, fall into the flask and multiply in the broth. Therefore, cells arise from existing cells.

The swan neck prevented airborne particles from entering.

Question 3

Robert Koch

Answer 3

Developed the agar plate technique. He used agar plates to isolate the microbe that caused the anthrax disease. It was not just caused from general uncleanliness, but from the anthrax bacillus.

Koch’s postulates were principles used to identify the specific microorganism responsible for a specific disease:

1. The micro-organism caused the disease in the host is isolated.
2. The micro-organism must be isolated and cultured in the laboratory and accurately described and recorded.
3. When a sample of the pure culture is innoculated into a healthy host, it would develop the same symptoms of the original host.
4. The same micro-organism must be able to be isolated from the second host, and identified as the same micro-organism.

Each disease is caused by a specific microorganism –> Nobel Prize.

Question 4

Pasture and Koch

Answer 4

Robert Koch: superior laboratory techniques, and proved that specific germs caused anthrax, cholera, tuberculosis. Koch’s postulates proved that specific germs cause specific diseases and that disease gers transmit disease from one body to another, are fundamental to germ theory.

Louis Pasteur:

Question 5

Timeline

dont worry about dates, just the order of events

Answer 5

1677: Antonie van Leeuwenhoek invented the microscope.

1857: Pasteur reasearch of sour wine. He proved that sterilised water in a closed flask stayed sterile, whilst sterilised water in an open flask bred germs.

1861: Pasteur published his Germ Theory

1876: Koch built upon Pasteur’s work by proving that specific microbes caused specific diseases - “Microbe hunting”. He used agar jelly to create solid cultures, stained bacteria, recorded findings with newly invented photography.

1877: Pasteur heard of Koch’s discovery of the anthrax bacteria, and started to compete to label new microbes.

1881: Pasteur showed that a weakened dose of anthrax bacteria on a sheep made them immune to the disease.
* Charles Chamberland’s error: injected chickens with a cholera culture that had been weakened by accident as it was left on the desk while on holiday. The chickens survived, and when injected with a fresh culture, they still survived.