Microbiology
Microbiology is the study of
microorganisms, which are
unicellular or cell-cluster
microscopic organisms. This includes
eukaryotes (with a
nucleus) such as
fungi and
protists, and
prokaryotes (without a nucleus) such as
bacteria and
viruses (though viruses are not strictly classed as living organisms).
Although much is now known in the field of microbiology, advances are being made regularly. In actual fact, the most common estimates suggest that we have studied only about 1% of all of the microbes in any given environment. Thus, despite the fact that over three hundred years have passed since the discovery of microbes, the field of microbiology is clearly in its infancy relative to other biological disciplines such as
zoology,
botany or even
entomology.
Bacteria were first observed by
Anton van Leeuwenhoek in
1676 using a single-lens microscope of his own design. The name "bacterium" was introduced much later, by
Ehrenberg in
1828, derived from the
Greek word βακτηριον meaning "small stick". While
Antony van Leeuwenhoek is often cited as the first
microbiologist, the first recorded microbiological observation, that of the fruiting bodies of molds, was made earlier in
1665 by
Robert Hooke.
The field of
bacteriology (later a subdiscipline of microbiology) is generally considered to have been founded by
Ferdinand Cohn (
1828-
1898), a botanist whose studies on algae and photosynthetic bacteria led him to describe several bacteria including
Bacillus and
Beggiatoa. Ferdinand Cohn was also the first to formulate a scheme for the taxonomic classification of bacteria.
Louis Pasteur (
1822-
1895) and
Robert Koch (
1843-
1910) were contemporaries of Cohn's and are often considered to be the founders of
medical microbiology. Pasteur is most famous for his series of experiments designed to disprove the then widely held
theory of spontaneous generation, thereby solidifying microbiology's identity as a biological science. Pasteur also designed methods for food preservation (
pasteurization) and vaccines against several diseases such as
anthrax, fowl cholera and
rabies. Robert Koch is best known for his contributions to the
germ theory of disease, proving that specific diseases were caused by specific pathogenic microorganisms. He developed a series of criteria that have become known as the
Koch's postulates. Koch was one of the first scientists to focus on the isolation of bacteria in
pure culture resulting in his description of several novel bacteria including
Mycobacterium tuberculosis, the causative agent of
tuberculosis.
While Louis Pasteur and Robert Koch are often considered the founders of microbiology, their work did not accurately reflect the true diversity of the microbial world because of their exclusive focus on microorganisms having medical relevance. It was not until the work of
Martinus Beijerinck (
1851-
1931) and
Sergei Winogradsky (
1856-
1953), the founders of
general microbiology (an older term encompassing aspects of microbial physiology, diversity and ecology), that the true breadth of microbiology was revealed. Martinus Beijerinck made two major contributions to microbiology: the discovery of
viruses and the development of enrichment culture techniques. While his work on the
Tobacco Mosaic Virus established the basic principles of virology, it was his development of
enrichment culturing that had the most immediate impact on microbiology by allowing for the cultivation of a wide range of microbes with wildly different physiologies. Sergei Winogradsky was the first to develop the concept of
chemolithotrophy and to thereby reveal the essential role played by microorganisms in geochemical processes. He was responsible for the first isolation and description of both nitrifying and nitrogen-fixing bacteria.
The field of microbiology can be generally divided into several subdisciplines:
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Microbial physiology: The study of how the microbial cell functions biochemically. Includes the study of microbial growth, microbial
metabolism and
microbial cell structure.
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Microbial genetics: The study of how genes are organised and regulated in microbes in relation to their cellular functions. Closely related to the field of
molecular biology.
*
Medical microbiology: The study of the role of microbes in human illness. Includes the study of microbial
pathogenesis and
epidemiology and is related to the study of disease
pathology and
immunology.
*
Veterinary microbiology: The study of the role in microbes in veterinary medicine.
*
Environmental microbiology: The study of the function and diversity of microbes in their natural environments. Includes the study of
microbial ecology, microbially-mediated
nutrient cycling,
geomicrobiology, microbial diversity and
bioremediation. Characterisation of key bacterial habitats such as the
rhizosphere and
phyllosphere.
*
Evolutionary microbiology: The study of the evolution of microbes. Includes the study of bacterial
systematics and
taxonomy.
*
Industrial microbiology: The exploitation of microbes for use in industrial processes. Examples include
industrial fermentation and
wastewater treatment. Closely linked to the
biotechnology industry. This field also includes
brewing, an important application of microbiology.
*
Aeromicrobiology: The study of Airborne Microorganisms.
*
Food Microbiology: The study of Microorganisms causing Food Spoilage.
While microbes are often viewed negatively due to their association with many human illnesses, microbes are also responsible for many beneficial processes such as
industrial fermentation (e.g. the production of
alcohol and
dairy products),
antibiotic production and as vehicles for cloning in higher organsisms such as plants. Scientists have also exploited their knowledge of microbes to produce biotechnologically important enzymes such as
Taq polymerase,
reporter genes for use in other genetic systems and novel molecular biology techniques such as the
yeast two-hybrid system.
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Biochemistry*
Biotechnology*
Genetics*
Geomicrobiology*
Immunology*
Medicine*
Mycology*
Virology*
Archaea*
Eukaryote*
Prokaryote*
Important publications in microbiology*
GIDEON Microbiology tutorial*
Online Microbiology textbook*
Nature Reviews Microbiology (
journal home)
*
Bacteriology textbook*
Microbiology News*
American Society for Microbiology*
Society for General Microbiology
