The advent of microbiology Microbiology influenced and affected

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

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

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

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

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

Seeing 3 Antonie van Leeuwenhoek (1632 – 1723) “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 6

Ideas Debunking 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 7

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 curvednecked vessels • These allowed the entry of air but not microorganisms 8

Germ theory Louis Pasteur • Solved the problem of bad wine fermentation • 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) • Later, using a similar approach he solved the problem plaguing silkworm production • Thus, “cause and effect” of using a particular microbe was demonstrated 9

Germ theory 2 Robert Koch (1843 – 1910) • Worked on what caused anthrax • 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 10

The “Golden Age” (1857 – 1914) Microbiology established as a science • Rapid progress led mainly by Koch and Pasteur • 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) 11

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) 12

Exclusion of microorganisms Antisepsis Sepsis Antisepsis toxic effects of microorganisms during infection measures 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 13

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 14

Control of microorganisms Heat treatment Pasteurisation • 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 Clostridium botulinum © Dennis Kunkel Swelling containing an endospore 15

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 easily destroyed) • Effectively not used in microbiology – difficulties (not all spores are destroyed/microbial growth between boilings) 16

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) 17

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

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 19

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

Immunization Jenner (1749 -1823) • Observation: Milkmaids; cowpox; smallpox • Hypothesis: Exposure to cowpox confers protection against smallpox • Experiment: Inoculated James Phipps with material from cowpox sores Small pox did not develop 21

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 theory of vaccinations against anthrax (1877) and rabies (1885) 22