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

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ch 1 historical developments

Ch.1 Historical Developments

Discovery of microorganisms

Golden Age of Microbiology

Disciplines of microbiology

discovery of microorganisms
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?
where do microbes come from
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

macroscopic studies of spontaneous generation

Aristotle: worms appear on decayed meat

Van Helmont: mice arise in a jar containing corn that was stored in the dark


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
microscopic studies of spontaneous generation

Needham Experiment:

Heat meat broth

Stopper the flask

Observe for growth


microbes arose even in boiled broth



Boiled broth in hermatically sealed flasks and no growth


Sterilize air by heating it

Schroeder & Dusch:

Air enters through sterile cotton & is not heated


Microscopic studies of spontaneous generation
outcomes of the great debate
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
contamination of media
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)
golden age of microbiology
Golden Age of Microbiology
  • Koch’s postulates
  • Lister’s sterilization experiments
  • Jenner’s vaccination experiments
  • Pasteur’s rabies vaccine
koch s postulates
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
koch s materials
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)
organisms isolated using koch s postulates
Organisms isolated using Koch’s Postulates
  • 1876: Koch ~ Bacillus anthracis – ?
  • 1879: Neisser ~ Neisseria gonorrhoeae – ?
  • 1882: Koch ~ Mycobacterium tuberculosis - ?
  • 1894: Yersin ~ Yersinia pestis - ?
lister s sterilization experiments
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
jenner s vaccination experiments
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
smallpox immunization
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
pasteur s rabies vaccine
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

disciplines of microbiology
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