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Salem Health: Infectious Diseases & Conditions, 2nd Edition

Microbiology

by Brandy Weidow, , M.S.

Category: Epidemiology

Definition

“Microbiology,” a term derived from Greek words essentially meaning “examination of small life,” is the study of microorganisms, a large and diverse group of microscopic organisms existing as single cells or cell clusters. Of note, viruses are also studied in microbiology, although they are not considered to be cellular. Microbes are distinct from animal and plant cells because they can, mostly, carry out their life processes (such as growth and reproduction) and survive independent of other cells or a host (with the exception of viruses).

In general, microorganisms can be divided into prokaryotes (organisms such as bacteria that lack a cell nucleus and other membrane-bound organelles), eukaryotes (organisms such as algae, fungi, and protists that have a cell nucleus), and viruses (noncellular organisms that rely on host cells for achievement of life processes and survival). Of note, in modern classification systems, prokaryotes are commonly further divided into the domains Bacteria and Archaea, whereby the latter domain represents microbes that are phylogenetically related to the former domain, but that have many structural, genetic, and biochemical distinctions. In general, eukaryotes are larger than prokaryotes, which are larger than viruses, although the range of each of these groups can vary widely.

History and Modern Progress

Scientists hypothesized the existence of microorganisms for many centuries before they were actually discovered, although these early claims were not based on observation or data. Robert Hooke is credited with publishing the first report of the fruiting bodies of molds in 1665, and he is notable for coining the term “cell” to refer to the basic unit of life. However, microbes were directly observed for the first time more than three hundred years ago, when Antoni van Leeuwenhoek designed a single-lens microscope for research purposes and reported the observation of bacteria and other microorganisms in 1676.

Louis Pasteur in his laboratory, observing an experiment. Image courtesy of Britannica Kids via Wikimedia Commons.

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Louis Pasteur and Robert Koch are considered the founders of microbiology and medical microbiology, respectively. Pasteur is well known for his experiments disproving the theory of spontaneous generation, giving microbiological studies a basis. Koch is best known for his contributions to the germ theory of disease, which proved that diseases were indeed caused by specific microbes called pathogens, or harmful microbes.

Robert Koch. Wellcome Images via Wikimedia Commons.

Since the early years of microbiological studies, the field has evolved tremendously. In particular, a few significant advances that have stemmed from microbiology include the development of antibiotics, vaccines, and bioremediation agents. However, because microbiology (and its various subdisciplines) is a relatively new field, it is still considered to be in its infancy, especially when compared with long-established disciplines such as botany and zoology.

Subdisciplines

The field of microbiology is tremendously broad, in that it includes a number of general areas, including bacteriology (the study of bacteria), mycology (the study of fungi), parasitology (the study of parasites), and virology (the study of viruses and, more recently, virus-like agents, including prions, viroids, and satellites). These areas can be further divided into a variety of subtopics. For example, a virologist can focus on deoxyribonucleic acid (DNA) viruses only. A microbiologist can, by definition, study any or all of these topics, although microbiology researchers typically specialize and practice in either of several scientific fields: human medicine, veterinary medicine, environmental studies, agricultural studies, food science, pharmaceuticals, and biotechnology and bioengineering, among many others. Furthermore, a researcher may also focus on a particular aspect of a certain microorganism or group or organisms, such as microbial growth, structure, metabolism, genetics, and evolution.

Because the immune system typically interacts with and influences microbes (especially pathogens), immunology is often coupled with the study of microbiology. Although immunology can be studied independently of microbiology (or in the context of other disciplines), these two fields are often coupled because much of the pertinent information intersects. Thus, many academic institutions offer joint programs in the study of both disciplines.

With modern advances in research, medicine, and technology, new subdisciplines of microbiology continue to emerge. For instance, nanomicrobiology and industrial microbiology are two fairly novel fields that study microbes at the nanoscale (nanomicrobiology) and study the use of microorganisms for the production of food or industrial products (industrial microbiology).

Impact

Harmful microbes (pathogens) make up a small fraction of the total population of microorganisms on Earth, yet they play a particularly powerful role in human life. Given the significance of these harmful microbes, microbiology is critical to the fields of health and medicine. In addition, because microbes contribute to the pathogenesis of many diseases that affect nonhuman animals, plants, water, and soil, for example, microbiology also plays a critical role in the environmental and agricultural sciences.

Even more, microbiology studies the microbes that are responsible for a number of beneficial processes, including antibody production (for treating humans, animals, and plants), fermentation (producing dairy products, alcohol, and other consumables), and a variety of other biotechnological applications in research and medicine (producing useful enzymes and amino acids).

Several agencies monitor and regulate the various aspects of infectious diseases associated with microbiological organisms. These agencies include the World Health Organization, the Centers for Disease Control and Prevention, the U.S. Food and Drug Administration, and the U.S. Environmental Protection Agency. With scientific researchers, clinicians, industry professionals, support organizations, and other contributors, these agencies work to advance knowledge of microbes, both good and bad.

Further Reading

1 

Gladwin, Mark, and Bill Trattler. Clinical Microbiology Made Ridiculously Simple. 4th ed. Miami: MedMaster, 2007.

2 

Madigan, Michael T., and John M. Martinko. Brock Biology of Microorganisms. 12th ed. Upper Saddle River, N.J.: Pearson/Prentice Hall, 2010.

3 

Ryan, Kenneth J., and C. George Ray, eds. Sherris Medical Microbiology: An Introduction to Infectious Diseases. 5th ed. New York: McGraw-Hill, 2010.

4 

Through the Microscope: A Look at All Things Small. Available at http://www.microbiologytext.com.

5 

Tortora, Gerard J., Berdell R. Funke, and Christine L. Case. Microbiology: An Introduction. 10th ed. San Francisco: Benjamin Cummings, 2010.

Web Sites of Interest

American Society for Microbiology

http://www.asm.org

Microbiology and Immunology On-line

http://pathmicro.med.sc.edu/book/welcome.htm

Microbiology Information Portal

http://www.microbes.info

Mycology Online

http://www.mycology.adelaide.edu.au

Todar’s Online Textbook of Bacteriology

http://www.textbookofbacteriology.net

U.S. Environmental Protection Agency

http://www.epa.gov/nerlcwww

Virology.net

http://www.virology.net

See also: Bacteria: Classification and types; Bacteria: Structure and growth; Bacterial infections; Bacteriology; Centers for Disease Control and Prevention (CDC); Epidemiology; Fungal infections; Fungi: Classification and types; Fungi: Structure and growth; Koch’s postulates; Microscopy; Parasites: Classification and types; Parasitic diseases; Pathogenicity; Pathogens; Prion diseases; protozoan diseases; Serology; Viral infections; Virology; Virulence; Viruses: Types; World Health Organization (WHO).

Citation Types

Type
Format
MLA 9th
Weidow, Brandy. "Microbiology." Salem Health: Infectious Diseases & Conditions, 2nd Edition, edited by H. Bradford Hawley, Salem Press, 2020. Salem Online, online.salempress.com/articleDetails.do?articleName=Infect2e_0357.
APA 7th
Weidow, B. (2020). Microbiology. In H. B. Hawley (Ed.), Salem Health: Infectious Diseases & Conditions, 2nd Edition. Salem Press. online.salempress.com.
CMOS 17th
Weidow, Brandy. "Microbiology." Edited by H. Bradford Hawley. Salem Health: Infectious Diseases & Conditions, 2nd Edition. Hackensack: Salem Press, 2020. Accessed September 16, 2025. online.salempress.com.