Ch.1 Historical Developments

1. Ch.1 Historical Developments Discovery of microorganisms Golden Age of Microbiology Disciplines of microbiology

2. Discovery of microorganisms • What is microbiology? • Study of small organisms generally too small to be seen with the naked eye • Biomass of Earth • 50% microorganisms • 35% plants • 15% animals • 1674: van Leeuwenhoek discovered “animalcules” • Father of microbiology • Interest in microbes came about because of 2 Qs: • Where do living things come from? • What causes disease?

3. Where do microbes come from? • Spontaneous generation Theory • 346 B.C. Aristotle: Life appears from nonliving, often decaying matter spontaneously • All organisms arise from other organisms like themselves (Pasteur) Experiments occur both on a macroscopic level and a microscopic level

4. Proponents Aristotle: worms appear on decayed meat Van Helmont: mice arise in a jar containing corn that was stored in the dark Opponents Redi: Experiments with rotting meat and flies Meat containers with lids Meat containers with nets Meat containers without lid or net Results: ??? Macroscopic studies of spontaneous generation

5. Proponents Needham Experiment: Heat meat broth Stopper the flask Observe for growth Results: microbes arose even in boiled broth Opponents Spallanzani: Boiled broth in hermatically sealed flasks and no growth Schwann: Sterilize air by heating it Schroeder & Dusch: Air enters through sterile cotton & is not heated Pasteur: Microscopic studies of spontaneous generation

6. Pasteur’s experiment for disproving spontaneous generation

7. Outcomes of the great debate • Microbes give rise to other like microbes • Methods to study microbes must prevent contamination ( entry of any organism) • Sterile materials required to prevent contamination • Sterilization: killing of all organisms • Pasteurization: reduction of numbers of organisms in fluids by heat

8. Contamination of media • Tyndall (1877) • Microbes were carried on dust particles in air • Microbes exist in two forms • Heat sensitive • Heat stable: requires repeated heating and cooling to kill, called Tyndallization • Cohn (1877) • Bacteria produced spores which where responsible for heat stable forms • Spores: resistant and dormant forms of some microbes (Bacillus anthracis)

9. Golden Age of Microbiology • Koch’s postulates • Lister’s sterilization experiments • Jenner’s vaccination experiments • Pasteur’s rabies vaccine

10. Koch’s postulates • Isolation: same organism can be found in all and only sick animals • Cultivation: organisms can be obtained and grown in pure cultures • Transference: inoculation of cultured cells into healthy animals transfers disease • Reisolation: same organism can be reisolated from the infected animal and cultured again

11. Koch’s Materials • Growth of microbes on solid nutrient media • Potato slices were clumpsy • Nutrient media in gelatin caused problems: • Melted during inoculations with heat • Some organisms digested it • Nutrient media in agar solves problems: • Polysaccharide from seaweed (Frau Hesse) • Dissolves and melts at ~100ºC, solidifies at ~45ºC • Petri dishes (Richard Petri)

12. Organisms isolated using Koch’s Postulates • 1876: Koch ~ Bacillus anthracis – ? • 1879: Neisser ~ Neisseria gonorrhoeae – ? • 1882: Koch ~ Mycobacterium tuberculosis - ? • 1894: Yersin ~ Yersinia pestis - ?

13. Lister’s sterilization experiments • Surgical procedures often resulted in death of the patient from bacterial infections • Defend against disease by eliminating germs • Lister used chemicals to sterilize operating rooms and surgical tools • Room and instruments sprayed with a phenol (carbolic acid) solution • Figure 1-10

14. Jenner’s vaccination experiments • Animals have natural defense mechanisms against disease • Immunity: resistance to disease • Phagocytes, antibodies • Immunology: study of mechanisms of immunity • Started with Jenner who developed the 1st vaccination for smallpox

15. Smallpox Immunization • Smallpox was caused by a that cannot be grown in culture on any laboratory media • Two forms of the disease: • Variola major (30% fatalities) • Variola minor (1% fatalities) • Survivor of either disease became immune to both • Variolation: deliberate infection w/ mild form (Variola minor) • Jenner noticed that milkmaids were also immune to smallpox but had attracted cowpox • Vaccination: Infection with cowpox

16. Pasteur’s rabies vaccine • No mild form of rabies ~all fatal • Reservoir generally dogs and cats • Attenuation**: method to reduce virulence of pathogen and then the less virulent form is used as vaccination • injected rabbits with rabies virus • took spinal fluid of infected rabbits for reinfection of other rabbits and then finally as a vaccine ** now use recombinant DNA to do this

17. Disciplines of microbiology • Chemotherapy (Erhlich) • Chemicals which act as ‘magic bullets’ to cure disease • Used arsenic to cure syphilis • Sulfa drugs in 1930 • Penicillin developed during WWII • Molecular Biology • Gene therapy, recombinant DNA technology • Microbial genetics, microbial ecology, pathogentic microbiology, immunology