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  1. Microbiology - An Introduction
    1. Microbiology is the study of organisms too small to be clearly seen by the unaided eye (i.e., microorganisms); these include viruses, bacteria, archaea, protozoa, algae, and fungi
    2. Some microbes (e.g., algae and fungi) are large enough to be visible, but are still included in the field of microbiology; it has been suggested that microbiology be defined not only by the size of the organisms studied but by techniques employed to study them (isolation, sterilization, culture in artificial media)
  2. The Discovery of Microorganisms
    1. Invisible living creatures were thought to exist and were thought to be responsible for disease long before they were observed
    2. Antony van Leeuwenhoek (1632-1723) constructed microscopes and was the first person to observe and describe microorganisms accurately
  3. The Conflict over Spontaneous Generation
    1. The proponents of the concept of spontaneous generation claimed that living organisms could develop from nonliving or decomposing matter
    2. Francesco Redi (1626-1697) challenged this concept by showing that maggots on decaying meat came from fly eggs deposited on the meat, and not from the meat itself
    3. John Needham (1713-1781) showed that mutton broth boiled in flasks and then sealed could still develop microorganisms, which supported the theory of spontaneous generation
    4. Lazzaro Spallanzani (1729-1799) showed that flasks sealed and then boiled had no growth of microorganisms, and he proposed that air carried germs to the culture medium; he also commented that external air might be needed to support the growth of animals already in the medium; the latter concept was appealing to supporters of spontaneous generation
    5. Louis Pasteur (1822-1895) trapped airborne organisms in cotton; he also heated the necks of flasks, drawing them out into long curves, sterilized the media, and left the flasks open to the air; no growth was observed because dust particles carrying organisms did not reach the medium, instead they were trapped in the neck of the flask; if the necks were broken, dust would settle and the organisms would grow; in this way Pasteur disproved the theory of spontaneous generation
    6. John Tyndall (1820-1893) demonstrated that dust did carry microbes and that if dust was absent, the broth remained sterile-even if it was directly exposed to air; Tyndall also provided evidence for the existence of heat-resistant forms of bacteria
  4. The Role of Microorganisms in Disease
    1. Recognition of the relationship between microorganisms and disease
      1. Agostino Bassi (1773-1856) showed that a silkworm disease was caused by a fungus
      2. M. J. Berkeley (ca. 1845) demonstrated that the Great Potato Blight of Ireland was caused by a fungus
      3. Louis Pasteur showed that the péine disease of silkworms was caused by a protozoan parasite
      4. Joseph Lister (1872-1912) developed a system of surgery designed to prevent microorganisms from entering wounds; his patients had fewer postoperative infections, thereby providing indirect evidence that microorganisms were the causal agents of human disease; his published findings (1867) transformed the practice of surgery
      5. 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:
        1. The microorganisms must be present in every case of the disease but absent from healthy individuals
        2. The suspected microorganisms must be isolated and grown in pure culture
        3. The same disease must result when the isolated microorganism is inoculated into a healthy host
        4. The same microorganism must be isolated again from the diseased host
      6. Koch's work was independently confirmed by Pasteur
    2. The development of techniques for studying microbial pathogens
      1. Koch and his associates developed techniques, reagents, and other materials for culturing bacterial pathogens on solid growth media; these enable microbiologists to isolate microbes in pure culture
      2. Charles Chamberland (1851-1908) constructed a bacterial filter that removed bacteria and larger microbes from specimens; this led to the discovery of viruses as disease-causing agents
    3. Immunological studies
      1. Edward Jenner (ca. 1798) used a vaccination procedure to protect individuals from smallpox
      2. Louis Pasteur developed other vaccines including those for chicken cholera, anthrax, and rabies
      3. Emil von Behring (1854-1917) and Shibasaburo Kitasato (1852-1931) induced the formation of diphtheria toxin antitoxins in rabbits; the antitoxins were effectively used to treat humans and provided evidence for humoral immunity
      4. Elie Metchnikoff (1845-1916) demonstrated the existence of phagocytic cells in the blood, thus demonstrating cell-mediated immunity
  5. Industrial Microbiology and Microbial Ecology
    1. Louis Pasteur demonstrated that alcoholic fermentations were the result of microbial activity, that some organisms could decrease alcohol yield and sour the product, and that some fermentations were aerobic and some anaerobic; he also developed the process of pasteurization to preserve wine during storage
    2. Sergei Winogradsky (1856-1953) worked with soil bacteria and discovered that they could oxidize iron, sulfur, and ammonia to obtain energy; he also studied anaerobic nitrogen fixation and cellulose decomposition
    3. Martinus Beijerinck (1851-1931) isolated aerobic nitrogen-fixing bacteria, a root-nodule bacterium capable of fixing nitrogen, and sulfate reducing bacteria
    4. Beijerinck and Winogradsky pioneered the use of enrichment cultures and selective media
  6. The Members of the Microbial World
    1. Procaryotes have a relatively simple morphology and lack a true membrane-delimited nucleus
    2. Eucaryotes are morphologically complex and have a true, membrane-enclosed nucleus
    3. In a commonly used classification scheme, organisms are divided into five kingdoms: the Monera or Procaryotae, Protista, Fungi, Animalia, and Plantae; microbiologists are concerned primarily with members of the first three kingdoms and also with viruses, which are not classified with living organisms
    4. Recently a classification scheme consisting of three domains (Bacteria, Archaea, and Eucarya) has become widely accepted; this scheme is followed in this textbook
  7. The Scope and Relevance of Microbiology
    1. Microorganisms were the first living organisms on the planet, live everywhere life is possible, are more numerous than any other kind of organism, and probably constitute the largest component of the earth's biomass
    2. The entire ecosystem depends on the activities of microorganisms, and microorganisms influence human society in countless ways
    3. Microbiology has an impact on many fields including medicine, agriculture, food science, ecology, genetics, biochemistry, and molecular biology
    4. Microbiologists may be interested in specific types of organisms:
      1. Virologists-viruses
      2. Bacteriologists-bacteria
      3. Phycologists or Algologists-algae
      4. Mycologists-fungi
      5. Protozoologists-protozoa
    5. Microbiologists may be interested in various characteristics or activities of microorganisms:
      1. Microbial morphology
      2. Microbial cytology
      3. Microbial physiology
      4. Microbial ecology
      5. Microbial genetics and molecular biology
      6. Microbial taxonomy
    6. Microbiologists may have a more applied focus:
      1. Medical microbiology, including immunology
      2. Food and dairy microbiology
      3. Public health microbiology
      4. Agricultural microbiology
      5. Industrial microbiology
  8. The Future of Microbiology
    1. Microbiology has had and will continue to have a profound influence on society.
    2. In the future microbiologists will be:
      1. Trying to better understand and control existing, emerging, and reemerging infectious diseases
      2. Studying the association between infectious agents and chronic diseases
      3. Learning more about host defenses and host-pathogen interactions
      4. Developing new uses for microbes in industry, agriculture, and environmental control
      5. Still discovering the many microbes that have not yet been identified and cultured
      6. Trying to better understand how microbes interact and communicate
      7. Analyzing and interpreting the ever-increasing amount of data from genome studies
      8. Continuing to use microbes as model systems for answering fundamental questions in biology
      9. Assessing and communicating the potential impact of new discoveries and technologies on society

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