1 The advent of microbiology Microbiology influenced and affected mankind before the knowledge of “invisible” organisms e.g. pestilence and disease A scene from the Black Plague Yersinia pestis © Dennis Kunkel

2 The advent of microbiology Microbiology influenced and affected mankind before the knowledge of “invisible” organisms e.g. alcoholic beverages; Making brew Yeast © Dennis Kunkel

3 The advent of microbiology The science of microbiology resulted from ideological and technological developments some of which are visited here

4 Seeing Robert Hooke (1635 – 1703) Micrographia (1660) Detailed drawings and descriptions of biological specimens “Cells” of cork

5 Seeing 2 Antonie van Leeuwenhoek (1632 – 1723) The first to see and describe bacteria (1676)

6 Seeing 3 “I discovered in a tiny drop of water, incredibly many very little animalcules, and these of diverse sorts and sizes. They moved with bendings, as an eel always swims with its head in front, and never tail first, yet these animalcules swam well backwards as forwards, though their motion was very slow.” June 16, 1675 Antonie van Leeuwenhoek (1632 – 1723)

7 Ideas Debunking the theory of the spontaneous generation of life (abiogenesis) Francesco Redi (1626 – 1697) Experiments on the origin of maggots (1668) Used meat in containers open/closed to flies Spallazani (1729 – 1799) Heated broths sealed in containers did not become cloudy with growth of microorganisms Opponents argued that air was required for abiogenesis

8 Ideas 2 Debunking spontaneous generation continued Schwann (1810 – 1882) Improved on previous experiments by allowing entry of heated air Opponents argued that heating air destroyed its ability to generate life Pasteur (1822 – 1895) Settled the issue by using curved- necked vessels These allowed the entry of air but not microorganisms

9 Germ theory Solved the problem of bad wine fermentation Louis Pasteur that consistently good wine is obtained when juice is heated to rid it of its associated microbes, and then subsequently inoculated with a specific microbe (from good wine) Thus, “cause and effect” of using a particular microbe was demonstrated Later, using a similar approach he solved the problem plaguing silkworm production

10 Germ theory 2 Worked on what caused anthrax Robert Koch (1843 – 1910) Found rod-shaped bacteria in the blood of diseased animals He isolated the bacterium from others When this bacterium was injected into mice, they developed the disease Again, “cause and effect” with a specific microbe was demonstrated This work, with that of Pasteur validated the germ theory of disease (1882) Koch Postulates (1884) are four criteria to prove a specific association between microbe and a disease

11 The “Golden Age” (1857 – 1914) Rapid progress led mainly by Koch and Pasteur Microbiology established as a science Discoveries in: Etiology, immunity and vaccines, techniques, and cure of disease e.g. Mycobacterium tuberculosis and Vibrio cholerae (Koch) Gram staining (Gram) Theory of immunity (Ehrlich) Clostridium tetani (Kitasato)

12 Exclusion of microorganisms Pure cultures The requirement for and importance of pure cultures Essential in the determination of physiological, biochemical and etiological characteristics How obtained Isolation: Separation and selection Solid media and plate culture Angelina Hesse (Agar; 1882) Julius Richard Petri (Dish; 1887)

13 Exclusion of microorganisms Antisepsis Sepsistoxic effects of microorganisms during infection Antisepsismeasures to prevent sepsis Oliver Wendell Holmes (1809 – 1894) Insisted that puerperal fever (serious infection after childbirth) is contagious (1843 i.e. before germ theory was established) Ignaz Phillip Semmelweis (1818 – 1865) Use of chlorine solution to disinfect hands of surgeons cut down mortality from puerperal fever

14 Exclusion of microorganisms Antisepsis 2 Joseph Lister (1827 – 1912) In 1864 Lister noted that 45% of his patients died from post-surgery infections He controlled infections by improving hygiene and the use of diluted phenol in dressings and to spray the operating room

15 Control of microorganisms Heat treatment Pasteurisation Clostridium botulinum © Dennis Kunkel Swelling containing an endospore Pasteur’s experiments on disproving abiogenesis established the use of heat to destroy microbes Pasteurization is the use of sub-boiling temperatures to destroy microbes However, not suitable for spore-formers

16 Control of microorganisms Heat treatment 2 Tyndallization John Tyndall (1820 – 1893) found that hay infusions boiled for 5 h still contained viable microbes Used 3 boiling cycles to allow spores to germinate (consequently more more easily destroyed) Effectively not used in microbiology – difficulties (not all spores are destroyed/microbial growth between boilings)

17 Control of microorganisms Heat treatment 2 Sterilization Extension of pasteurization and tyndallization Heat treatment with moist steam at temperatures > boiling e.g. 121 o C, using an autoclave (vessel within which steam is raised under pressure)

18 Control of microorganisms Chemotherapy Chemicals 1600s to mid 1800s cinchona bark was the most used treatment for malaria Quinine In 1820 a quinoline alkaloid in the bark which provided the highest anti- malarial effect was isolated and named Quinine 1944 the quinoline alkaloid synthesized in the laboratory

19 Control of microorganisms Chemotherapy 2 Chemicals Paul Ehrlich (1854 – 1915) Looked for “magic bullets” that would kill microbes but not human cells Salvarsan (1910), an arsenic compound for treating syphilis

20 Control of microorganisms Chemotherapy 2 Antibiotics Alexander Fleming Penicillin (1928) Inhibition zone Penicillium notatum Bacterial colonies

21 Immunization Jenner ( ) Hypothesis: Exposure to cowpox confers protection against smallpox Experiment: Inoculated James Phipps with material from cowpox sores Small pox did not develop Observation: Milkmaids; cowpox; smallpox

22 Immunization Pasteur 1880 Used Koch’s methods to isolate and culture the bacterium that causes chicken cholera Routinely caused chickens to die when inoculated with the bacterium But one experiment failed Discovered that the culture was old He had stumbled on avirulence Acknowledging the work of Jenner, he validated the theory of vaccinations against anthrax (1877) and rabies (1885)