Lecture 1A - History of Microbiology

History of Microbiology

What does life look like? First Recorded Observations of Microbes Businessman Used the previous work of Robert Hooke (English philosopher), who published in 1665 his observations with microscopes; coined the word “cell” Leeuwenhoek refused to tell others how he made his lenses, so he had a monopoly His lenses were of superior quality Called the “father of microbiology” Antony van Leeuwenhoek

Early Microscopy ~1670 Antony van Leeuwenhoek made hand-held lenses ~300X magnification first to observe live microbes – “animalcules”

What major contribution was made by Hooke? What major contribution was made by van Leeuwenhoek?

The Golden Age of Microbiology Scientists searched for answers to four questions Is spontaneous generation of microbial life possible? What causes fermentation? What causes disease? How can we prevent infection and disease? 6

Spontaneous Generation vs. Biogenesis Spontaneous Generation – life arises from non-living things (soil, the environment, bad air) Biogenesis – life arises only from living organisms, which may be too small to see

Spontaneous Generation vs. Biogenesis Francesco Redi - 1668 Question: What causes maggots on rotting meat? Observation: Meat attracts flies Hypothesis: Meat forms maggots when flies are present Method: Meat placed in open and covered jars First person to challenge theory of spontaneous generation by demonstrating that maggots comes from eggs laid by flies.

Spontaneous Generation vs. Biogenesis Francesco Redi - 1668 Results: Only open jars produced maggots Conclusion: Results support hypothesis Maggots form only when flies are present and allowed to leave their larvae on meat. Rotting meat does not spontaneously produce maggots.

Spontaneous Generation vs. Biogenesis Louis Pasteur 1861 Hired by Napoleon III to determine the cause of souring in wine. Found that many wineries in France were afflicted by some disease, souring or preventing flavor in wine Found that sterile grape juice would not ferment into wine Deduced that natural source of yeast was found on skin of grape Was criticized, because this did not follow laws of spontaneous generation, which was held true by some Pasteur crushed “spontaneous generation” using the swan necked flask experiments “swan-necked” flasks

Spontaneous Generation vs. Biogenesis Louis Pasteur 1861 Question: What causes growth of microbes in broth? Observations: Open broth containers  Broth heated & covered  Hypothesis: Heating & and blocking airborne microorganisms from entering the flask (using a swan-necked flask) prevents microbial growth Method: Boiled broth in regular, open or swan-necked flasks Flasks were observed for several days

Spontaneous Generation vs. Biogenesis Louis Pasteur 1861 Results: Regular, open flasks – Swan-necked flasks – Conclusions: Hypothesis supported Heating in swan-necked flasks where airborne microbes cannot fall into the broth prevents growth of microbes Microbes do not arise spontaneously in broth Led to the idea and use of aseptic techniques

Fermentation and Pasteurization Why did beer/wine sour? Yeast converts sugar to alcohol without air. With air, alcohol is converted to acetic acid by bacteria. Acetobacter species convert ethanol to acetic acid in the presence of oxygen. Spoil wine. Used to make vinegar intentionally from wine.

Fermentation and Pasteurization Pasteurization (1864) is the application of high heat for a short time Gentle heat kills most bacteria Gentle heat = 55 C Developed rabies vaccine. Figure 1.4

What were the major contributions of the following scientists? Pasteur Redi Leeuwenhoek Hooke 2. Explain pasteurization. 3. What is fermentation? 4. Explain the relevance Pasteur’s swan-necked flask experiments.

Joseph Lister Pioneer of surgical antisepsis. Lister published in 1867: Phenol applied to wound prevents infection Surgeons should disinfect between patients with 5% phenol Surgical instruments should be disinfected 5% phenol should be sprayed in operating room Father of modern surgery

Germ Theory of Disease – Koch’s Postulates Robert Koch – 1876 Proved bacteria cause disease Studied anthrax cattle disease Developed “Germ Theory” “Koch’s Postulates” – a sequence of experimental steps that verified the germ theory. Developed pure culture methods

Koch’s Postulates Observation Cultivation

Koch’s Postulates Introduction

Koch’s Postulates Recovery

Koch’s Postulates Observation of disease signs & symptoms Cultivation of organism in pure culture Introduction of pure culture into healthy experimental animal Recovery of same organism from experimental animals

Significance of Koch’s Postulates scientific method to prove causation of disease links specific organisms with specific diseases gives a target for treatment of disease Microbes cause disease!!! can test treatments on cultured organism in the laboratory

What were the major contributions of the following scientists? Pasteur Redi Koch Leeuwenhoek Lister Hooke Explain Koch’s postulates and why they are medically relevant. Contrast spontaneous generation and biogenesis.