Microbiology - An Introduction

Subject: Microbiology - An Introduction Wed Feb 18, 2009 7:16 pm

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
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)

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
</li>
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
</li>
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
    </li>
  6. Koch's work was
    independently confirmed by Pasteur
  </li>
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
  </li>
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
  </li>
</li>
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
</li>
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
</li>
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
  </li>
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
  </li>
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
  </li>
</li>
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
  </li>
</li>

» HISTORY OF MICROBIOLOGY