Chapter 1 : Introduction to Microbiology

Topics covered in this snack-sized chapter:



Introduction to Microbiology arrow_upward


  • Microbiology is the study of microorganisms, which are tiny organisms that live around us and inside our body.
  • The study of living things those are too small to see without magnification. For example:
    • Viruses
    • Bacteria
    • Fungi
    • Algae
    • Protozoans
  • Some organisms studied by microbiologists can be visualized without the aid of amplification.
    • These organisms are included in the discipline of microbiology because of similarities in the properties and techniques used to study them.
  • Techniques necessary to isolate and culture microorganisms are:
    • Isolation
    • Sterilization
    • Culture in artificial media
  • Microbiologists may be interested in specific types of organisms:
    • Virologists – Viruses
    • Bacteriologists – Bacteria
    • Phycologists or Algologists – Algae
    • Mycologists – Fungi
    • Protozoologists – Protozoa
  • Microbiologists may have a more applied focus:
    • Medical microbiology, including immunology
    • Food and dairy microbiology
    • Public health microbiology
    • Industrial microbiology
    • Agricultural microbiology

    Role of Microorganisms in Disease arrow_upward


  • The following list is made up of the microbiologists and chemists who discovered the role of microorganisms in disease.
  • Agostino Bassi (1773 - 1856):
    • Showed that a silkworm disease was caused by a fungus
  • M. J. Berkeley (ca. 1845):
    • Demonstrated that the Great Potato Blight in Ireland was caused by a fungus
  • Louis Pasteur (1822-1895):
    • Showed that the pebrine disease of silkworms was caused by a protozoan parasite
  • Joseph Lister (1827 - 1912):
    • Developed a system of surgery designed to prevent microorganisms from entering wounds – phenol sprayed in the air around a surgical incision.
    • Decreased number of post-operative infections in patients
    • His published findings (1867) transformed the practice of surgery.
  • Charles Chamberland (1851 - 1908):
    • Identified viruses as disease-causing agents – Tobacco Mosaic Virus
  • Edward Jenner (ca. 1798):
    • Used a vaccination procedure to protect individuals from smallpox
  • Louis Pasteur (1822-1895):
    • Developed other vaccines including those for chicken cholera, anthrax, and rabies
  • Ignaz Semmelweiss (~1850): Demonstrated that childbed fever (puerperal fever), caused by streptococcal infections, and was transmitted to patients by doctor’s hands.
    • Pioneer of antisepsis in obstetrics
    • Women giving birth in hospitals by medical students and physicians were 4x more likely to contract puerperal fever compared to those by midwives.
  • Emil von Behring (1854 - 1917) and Shibasaburo Kitasato (1852 - 1931):
    • Induced the formation of diphtheria tetanus antitoxins in rabbits which were effectively used to treat humans; thus demonstrating humeral immunity.
  • Elie Metchnikoff (1845 - 1916):
    • Demonstrated the existence of phagocytic cells in the blood, thus demonstrating cell-mediated immunity.
  • Robert Koch (1843 - 1910):
    • Using criteria developed by his teacher, Jacob Henle (1809-1895), established the relationship between Bacillus anthracis and anthrax.
    • His criteria became known as Koch’s Postulates and are still used to establish the link between a particular microorganism and a particular disease.

    Koch’s Postulates arrow_upward


  • Four criteria were established by Robert Koch to identify the causative agent of a particular disease, these include:
    • The microorganism or other pathogen must be present in all cases of the disease.
    • The pathogen can be isolated from the diseased host and grown in pure culture.
    • The pathogen from the pure culture must cause the disease when inoculated into a healthy, susceptible laboratory animal.
    • The pathogen must be reisolated from the new host and shown to be the same as the originally inoculated pathogen.


    Thank You from Kimavi arrow_upward


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