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Historical Background. Discovery of microorganisms Spontaneous generation vs. Biogenesis Pure culture technique Significance of microbes. Discovery of Microbes. Anton van Leeuwanhoek Mid-1600s Developed early microscope First to observe microbes: “animicules”

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historical background
Historical Background
  • Discovery of microorganisms
  • Spontaneous generation vs. Biogenesis
  • Pure culture technique
  • Significance of microbes
discovery of microbes
Discovery of Microbes
  • Anton van Leeuwanhoek
    • Mid-1600s
    • Developed early microscope
    • First to observe microbes: “animicules”
    • Did not appreciate the significance or impact of microbes on human life
spontaneous generation vs biogenesis
Spontaneous Generation vs Biogenesis
  • Aristotle
    • Suggested that mice could develop by spontaneous generation
  • Redi
    • Mid-1600s
    • Experimentally demonstrated that maggots (fly larvae) do not develop via spontaneous generation
spontaneous generation vs biogenesis4
Spontaneous Generation vs Biogenesis
  • Needham vs Spallanzani
    • Mid-1700s
    • Spallanzani demonstrated that microbes do not develop by spontaneous generation in sterile nutrient media sealed in flasks
    • Needham criticized Spallanzani’s work: asserted that spontaneous generation required fresh air in the flask
spontaneous generation vs biogenesis5
Spontaneous Generation vs Biogenesis
  • Pasteur
    • Mid to late-1800s
    • French chemist and a “founder” of the modern science of microbiology
    • Settled the Spallanzani-Needham debate with the “swan-necked flask” experiment
    • Worked on many important problems in microbiology, most notably in vaccine production
    • Aseptic technique
spontaneous generation vs biogenesis6
Spontaneous Generation vs Biogenesis
  • Tyndall
    • Late 1800s
    • Demonstrated directly that the growth of microbes in contaminated flasks was due to microbial cells from airborne dust particles, not from spontaneous generation
    • Developed a method (tyndallization) to ensure sterilization of media through repeated boiling
pure culture technique
Pure Culture Technique
  • Pure culture
    • A sample of microbial growth that contains only a single species
    • Challenging to obtain because of the large numbers and small sizes of microbes
  • Early attempts
    • “Limiting dilution” method in broth medium used by Pasteur and others
    • Difficult to ensure that a single species exists in the culture
pure culture technique8
Pure Culture Technique
  • Streak plate method
    • Developed in the 1870s by Koch and his co-workers
    • The objective: to obtain isolated colonies – spots of microbial growth that come from a single parent cell
    • The method: streak the sample on semisolid medium, containing a gelling agent
    • Agar: the most commonly used gelling agent
significance of microbes
Significance of Microbes
  • Microbes and disease: late 1700s – late 1800s
    • Jenner – small pox vaccine
    • Snow – epidemic control via public health measures
    • Semmelweis – importance of hand-washing
    • Lister – antiseptic surgical methods
    • Pasteur – rabies vaccine
    • Koch – isolated anthrax and tuberculosis bacteria; Developed Koch’s postulates
significance of microbes12
Significance of Microbes
  • Microbes and the environment: late 1800s
    • Winogradsky, Beijerinck, and others: established the role of microbes in biogeochemical cycling
  • Twentieth century microbiology
    • Public health microbiology
    • Discovery of viruses
    • Antimicrobial chemotherapy
    • Microbial cell structure and biochemistry
    • Microbial genetics and genetic engineering