Lecture 2: History and scope Flashcards
What was the reaction to Redi’s experiment?
People didn’t really believe that he’d disproven spontaneous generation. It raised more questions, notably whether microorganisms caused decomposition or vice versa.
What did Needham and Spallanzani do? How were their experiments perceived?
They both did similar experiments after Redi’s, putting broth in a flask and sealing it. Needham boiled the broth before putting it in the flash, and microorganisms appeared, seemingly supporting spontaneous generation. Spallanzani boiled it after putting it in the flash and no microorganisms appeared, seemingly disproving spontaneous generation.
After these experiments, it was thought that maybe spontaneous generation requires air.
How was spontaneous generation finally disproven?
It was disproven after a competition held by the French Academy of Science. Louis Pasteur boiled meat broth in a flash with a curved (swan) neck, while allowed air to enter but not dust, as it accumulated in the curve of the neck. No microorganisms developed. But when he broke off the neck or tilted the brother into the neck where the dust was, microorganisms did grow. This disproved spontaneous generation.
Explain Tyndall’s experiment and what it proved.
It supported Pasteur’s swan neck flask experiment, which implied that microorganisms are carried by dust. He let dust settle in a closed box coated with glycerin to trap the dust and prevent it from touching the tubes. He then filled the tubes in the box with broth and boiled it. The box also had curved tubes that allowed air to enter but not dust. No microorganisms appeared even after a long time.
Before microbiology, what were the believed sources of disease?
Supernatural forces, poisonous vapours from miasma (rotting smell), and imbalances between the four humours (fluids) of the body: blood, phlegm, yellow bile, and black bile.
What is the germ theory of disease? Who started it?
The germ theory of disease is the theory that microorganisms are the cause of disease. it was prompted by Agostino Bassi, who showed that a fungus could cause disease in silkworms.
Explain the role of Berkeley and Pasteur in supporting the germ theory of disease.
Berkeley showed that the great potato blight of Ireland was also caused by a fungus.
Pasteur showed that silkworms were parasitized by a protozoan (go back to lecture recording)
What did Lister do?
He was a surgeon influenced by Pasteur’s work, which showed that heat and phenol could kill microorganisms. He started heat sterilizing his instruments and using phenol on surgical dressings and wounds, and this was highly effective in preventing infections. His success suggested the role of microorganisms in causing disease.
Who are the two fathers of microbiology? What did they each do?
Pasteur and Koch. Pasteur did the swan neck flask experiment and showed that heat and phenol could kill microorganisms. Koch demonstrated that a bacterium was causing anthrax.
Explain how Koch showed that a bacterium caused anthrax.
He injected healthy mice with biological material by transferring anthrax through 20 mice. He then incubated a piece of spleen from the 20th mouse in beef broth, which caused endospores to grow. The endospores were then isolated and injected into healthy mice, which also developed anthrax.
What are Koch’s postulates?
They pertain to demonstrating the relationship between a microorganisms and a specific disease.
1. The microorganism must be present in every case of the disease but absent from healthy organisms.
2. The suspected microorganisms must be isolated and grown in a pure culture.
3. The same disease must result when the isolated microorganism is innoculated into a healthy host.
4. The same microorganism must be isolated again from the diseased host.
Describe three challenges involved in the development of techniques and how they were resolved (and by whom).
- To isolate suspected pathogens, working with liquid cultures was too hard due to the mix of many microorganisms. The solution was to grow bacteria on a solid surface so as to separate the microorganisms.
- Growing bacteria was too hard on gelatin, because it is degraded by microorganisms and melts at 37 degrees, which is the optimal growth temperature for human pathogens. Hesse suggested agar.
- Also had to determine the type of cover to use to prevent dust entering but that still allows oxygen to enter to allow growth. The solution was the Petri dish, developed by Richard Petri.
- Needed media similar to body fluids, as pathogens often adapt to thrive in the human body. This was developed by Kock.
Where did the concept of immunology come from?
Once more was known about bacteria and pathogens, we sought to understand why some people got infected and survived and others died, and why some people never got sick in the first place.
What did Edward Jenner do?
He is considered the father of immunology. He immunized people against smallpox using the cowpox virus (fluid from cowpox blisters) and saved more lives than the work of any other human in history.
What role did Louis Pasteur play in immunological studies?
He created the first attenuated live vaccine. He grew pure culture of human pathogens and grew them in environments that made them less effective (high temperature or in potassium bichromate). They could then confer immunity for avian cholera and rabies.
