Explain the theories explaining the history of Microbiology.

(A) Leeuwenhoek (1632 -1723)
• First scientist to use microscopes to observe microorganisms.
• Made small hand held microscopes. He called micro-organisms “animalcules”

(B) Robert Hooke
He first described “culture” (small rooms) in cork in 1665. His discovery led to the formulation of the cell theory, which states that cells are the basic organizational unit of all living things.

(C) Redi & Spontaneous Generation
• Living organisms arise from non-living things (e.g.) maggots come from rotting meat.
• Francisco Redi – late I6oo’s showed that maggots developed only in meat that flies could reach to lay eggs on.

(D) Needham vs Spallanzani – Still trying to prove or disprove the theory of spontaneous generation.
Knew boiling killed microbes, so he would boil chicken broth, put it in a flask and seal it. If microbes grew, then it could only be only because of spontaneous generation. They did grow.
NB: Known microbes grew because the flask was not sterilized before he poured in the broth.
Spallanzani – Was not convinced by Needham’s experiment. He put broth in a flask, sealed it and boiled it. There were no microbes in the cooled broth.

(E) Pasteur’s Epic Experiments (1859)
• To offset the argument that air was necessary for spontaneous generation
• Pasteur allowed the free passage of air, but prevented the entry of microbes.
• He boiled meat broth in a flask and covered the neck of the flask in a flame. No microbes grew in the flask.
• When he tilted the flask so some broth flowed into the curved neck and then tilted it back so the broth was returned to the base of the flask. Microbes grew.
• Gravity had caused the microbes to settle at the low point of the neck, never reaching the broth in the base until the broth washed them in.
Pasteur’s experiment proved that
? No living things arise by spontaneous generation
? Microbes are everywhere – even in air and dust
? The growth of microbes causes dead plant and animal tissue to decompose and food to spoil. This led him to develop the technique of pasteurization to keep wine from spoiling.
NB. Pasteur also contributed to the development of vaccines

(F) The Germ Theory of Disease
Robert Koch – late 1870s
What is the germ theory of disease?
Microbes (germs) cause disease and specific microbes cause specific diseases.

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Kavungya answered the question on March 12, 2019 at 12:59