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Historical Background


Historical Background Discovery of microorganisms Spontaneous generation vs. Biogenesis Pure culture technique Significance of microbes Discovery of Microbes Anton ... – PowerPoint PPT presentation

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Title: Historical Background

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
  • Did not appreciate the significance or impact of
    microbes on human life

Spontaneous Generation vs Biogenesis
  • Aristotle
  • Suggested that mice could develop by spontaneous
  • Redi
  • Mid-1600s
  • Experimentally demonstrated that maggots (fly
    larvae) do not develop via spontaneous generation

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 Spallanzanis work asserted
    that spontaneous generation required fresh air in
    the flask

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 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
  • 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 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

Pure Culture Technique
Pure Culture Technique
Significance of Microbes
  • Microbes and disease late 1700s late 1800s
  • Jenner small pox vaccine
  • Snow epidemic control via public health
  • Semmelweis importance of hand-washing
  • Lister antiseptic surgical methods
  • Pasteur rabies vaccine
  • Koch isolated anthrax and tuberculosis
    bacteria Developed Kochs postulates

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
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