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An agar plate streaked with microorganisms Colonies de legionelles.jpg
An agar plate streaked with microorganisms

Bacteriology is the branch and specialty of biology that studies the morphology, ecology, genetics and biochemistry of bacteria as well as many other aspects related to them. This subdivision of microbiology involves the identification, classification, and characterization of bacterial species. [1] Because of the similarity of thinking and working with microorganisms other than bacteria, such as protozoa, fungi, and viruses, there has been a tendency for the field of bacteriology to extend as microbiology. [2] The terms were formerly often used interchangeably. [3] However, bacteriology can be classified as a distinct science.



Bacteriology is the study of bacteria and their relation to medicine. Bacteriology evolved from physicians needing to apply the germ theory to test the concerns relating to the spoilage of foods and wines in the 19th century. Identification and characterizing of bacteria being associated to diseases led to advances in pathogenic bacteriology. Koch's postulates played a role into identifying the relationships between bacteria and specific diseases. Since then, bacteriology has had many successful advances like effective vaccines, for example, diphtheria toxoid and tetanus toxoid. There have also been some vaccines that were not as effective and have side effects for example, typhoid vaccine. Bacteriology has also provided discovery of antibiotics.[ citation needed ]


A bacteriologist is a microbiologist or a professional [4] trained in bacteriology. The duties of a bacteriologist primarily include prevention, diagnosis and prognosis of diseases. Alongside health care, they may carry out various functions such as epidemiological surveillance, quality auditing with biotechnology development, basic research, management and teaching related to the career, scientist management, laboratory coordination and blood banks. [5]


Antonie van Leeuwenhoek, the first microbiologist and the first person to observe bacteria using a microscope. Anthonie van Leeuwenhoek (1632-1723). Natuurkundige te Delft Rijksmuseum SK-A-957.jpeg
Antonie van Leeuwenhoek, the first microbiologist and the first person to observe bacteria using a microscope.
Louis Pasteur in his laboratory, painting by A. Edelfeldt in 1885 Albert Edelfelt - Louis Pasteur - 1885.jpg
Louis Pasteur in his laboratory, painting by A. Edelfeldt in 1885
Statue of Koch in Berlin Statue of Robert Koch in Berlin.jpg
Statue of Koch in Berlin

Bacteria were first observed by the Dutch microscopist Antonie van Leeuwenhoek in 1676, using a single-lens microscope of his own design. He then published his observations in a series of letters to the Royal Society of London. [6] His observations had also included protozoans which he called animalcules. [7]

Christian Gottfried Ehrenberg introduced the word "bacterium" in 1828. [8] In fact, his Bacterium was a genus that contained non-spore-forming rod-shaped bacteria, [9] as opposed to Bacillus, a genus of spore-forming rod-shaped bacteria defined by Ehrenberg in 1835. [10]

Louis Pasteur demonstrated in 1859 that the growth of microorganisms causes the fermentation process, and that this growth is not due to spontaneous generation (yeasts and molds, commonly associated with fermentation, are not bacteria, but rather fungi). Along with his contemporary Robert Koch, Pasteur was an early advocate of the germ theory of disease. [11] Before them, Ignaz Semmelweis and Joseph Lister had realised the importance of sanitized hands in medical work. Semmelweis ideas was rejected and his book on the topic condemned by the medical community, but after Lister doctors started sanitizing their hands in the 1870s. While Semmelweis who started with rules about handwashing in his hospital in the 1840s predated the spread of the ideas about germs themselves and attributed diseases to "decomposing animal organic matter", Lister was active later. [12]

The discovery of the connection of microorganisms to disease can be dated back to the nineteenth century, when German physician Robert Koch introduced the science of microorganisms to the medical field. [13] He identified bacteria as the cause of infectious diseases and process of fermentation in diseases. [14] [15] [16] Koch, a pioneer in medical microbiology, worked on cholera, anthrax and tuberculosis. In his research into tuberculosis Koch finally proved the germ theory, for which he received a Nobel Prize in 1905. [17] In Koch's postulates, he set out criteria to test if an organism is the cause of a disease, and these postulates are still used today. [18] Louis Pasteur developed techniques to produce vaccines. Both Koch and Pasteur played a role in improving antisepsis in medical treatment. This had an enormous positive effect on public health and gave a better understanding of the body and diseases. In 1870-1885 the modern methods of bacteriology technique were introduced by the use of stains and by the method of separating mixtures of organisms on plates of nutrient media. Between 1880 and 1881 Pasteur produced two successful vaccinations for animals against diseases caused by bacteria and it was successful. The importance of bacteria was recognized as it led to a study of disease prevention and treatment of diseases by vaccines. [14] [15] [16]

Ferdinand Cohn is said to be a founder of bacteriology, studying bacteria from 1870. Cohn was the first to classify bacteria based on their morphology. [19] [20]

Though it was known in the nineteenth century that bacteria are the cause of many diseases, no effective antibacterial treatments were available. [21] In 1910, Paul Ehrlich developed the first antibiotic, by changing dyes that selectively stained Treponema pallidum —the spirochaete that causes syphilis—into compounds that selectively killed the pathogen. [22] Ehrlich had been awarded a 1908 Nobel Prize for his work on immunology, and pioneered the use of stains to detect and identify bacteria, with his work being the basis of the Gram stain and the Ziehl–Neelsen stain. [23]

A major step forward in the study of bacteria came in 1977 when Carl Woese recognised that archaea have a separate line of evolutionary descent from bacteria. [24] This new phylogenetic taxonomy depended on the sequencing of 16S ribosomal RNA, and divided prokaryotes into two evolutionary domains, as part of the three-domain system. [25] Bacteriology has developed and can be studied in agriculture, marine biology, water pollution, bacterial genetics and biotechnology. [14] [15] [16]

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Robert Koch 19/20th-century German physician and bacteriologist

Heinrich Hermann Robert Koch was a German physician and microbiologist. As the discoverer of the specific causative agents of deadly infectious diseases including tuberculosis, cholera, and anthrax, he is regarded as one of the main founders of modern bacteriology. As such he is popularly nicknamed the father of microbiology, and as the father of medical bacteriology. His discovery of the anthrax bacterium in 1876 is considered as the birth of modern bacteriology. His discoveries directly provided proofs for the germ theory of diseases, and the scientific basis of public health.

Louis Pasteur French chemist and microbiologist

Louis Pasteur was a French chemist and microbiologist renowned for his discoveries of the principles of vaccination, microbial fermentation, and pasteurization. His research in chemistry led to remarkable breakthroughs in the understanding of the causes and preventions of diseases, which laid down the foundations of hygiene, public health and much of modern medicine. His works are credited to saving millions of lives through the developments of vaccines for rabies and anthrax. He is regarded as one of the founders of modern bacteriology and has been honored as the "father of bacteriology" and as the "father of microbiology".

Microorganism Microscopic living organism

A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells.

Infection Invasion of an organisms body by pathogenic agents

An infection is the invasion of an organism's body tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agents and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable disease, is an illness resulting from an infection.

Kochs postulates Four criteria showing a causal relationship between a causative microbe and a disease

Koch's postulates are four criteria designed to establish a causative relationship between a microbe and a disease. The postulates were formulated by Robert Koch and Friedrich Loeffler in 1884, based on earlier concepts described by Jakob Henle, and refined and published by Koch in 1890. Koch applied the postulates to describe the etiology of cholera and tuberculosis, both of which are now ascribed to bacteria. The postulates have been controversially generalized to other diseases. More modern concepts in microbial pathogenesis cannot be examined using Koch's postulates, including viruses and asymptomatic carriers. They have largely been supplanted by other criteria such as the Bradford Hill criteria for infectious disease causality in modern public health, and Falkow's criteria for microbial pathogenesis.

Germ theory of disease Prevailing theory about diseases

The germ theory of disease is the currently accepted scientific theory for many diseases. It states that microorganisms known as pathogens or "germs" can lead to disease. These small organisms, too small to see without magnification, invade humans, other animals, and other living hosts. Their growth and reproduction within their hosts can cause disease. "Germ" may refer to not just a bacterium but to any type of microorganism, such as protists or fungi, or even non-living pathogens that can cause disease, such as viruses, prions, or viroids. Diseases caused by pathogens are called infectious diseases. Even when a pathogen is the principal cause of a disease, environmental and hereditary factors often influence the severity of the disease, and whether a potential host individual becomes infected when exposed to the pathogen. Pathogens are diseases that can pass from one individual to another, both in humans and animals. Infectious diseases are caused by biological agents such as pathogenic microorganisms as well as parasites.

Pathophysiology – a convergence of pathology with physiology – is the study of the disordered physiological processes that cause, result from, or are otherwise associated with a disease or injury. Pathology is the medical discipline that describes conditions typically observed during a disease state, whereas physiology is the biological discipline that describes processes or mechanisms operating within an organism. Pathology describes the abnormal or undesired condition, whereas pathophysiology seeks to explain the functional changes that are occurring within an individual due to a disease or pathologic state.

Pasteur Institute French disease research organization

The Pasteur Institute is a French non-profit private foundation dedicated to the study of biology, micro-organisms, diseases, and vaccines. It is named after Louis Pasteur, who invented pasteurization and vaccines for anthrax and rabies. The institute was founded on June 4, 1887, and inaugurated on November 14, 1888.

Kiyoshi Shiga Japanese physician

Kiyoshi Shiga was a Japanese physician and bacteriologist. He had a well-rounded education and career that lead to many scientific discoveries. In 1897, Shiga was credited with the discovery and identification of the Shigelladysenteriae microorganism which causes dysentery, and the Shiga toxin which is produced by the bacteria. He conducted research on other diseases such as tuberculosis and trypanosomiasis, and made many advancements in bacteriology and immunology.

Ziehl–Neelsen stain A type of acid-fast stain

Ziehl–Neelsen staining is a type of acid-fast stain, first introduced by Paul Ehrlich. Ziehl–Neelsen staining is a bacteriological stain used to identify acid-fast organisms, mainly Mycobacteria. It is named for two German doctors who modified the stain: the bacteriologist Franz Ziehl (1859–1926) and the pathologist Friedrich Neelsen (1854–1898).

Asepsis Absence of disease-causing microorganisms

Asepsis is the state of being free from disease-causing micro-organisms. There are two categories of asepsis: medical and surgical. The modern day notion of asepsis is derived from the older antiseptic techniques, a shift initiated by different individuals in the 19th century who introduced practices such as the sterilizing of surgical tools and the wearing of surgical gloves during operations. The goal of asepsis is to eliminate infection, not to achieve sterility. Ideally, a surgical field is sterile, meaning it is free of all biological contaminants, not just those that can cause disease, putrefaction, or fermentation. Even in an aseptic state, a condition of sterile inflammation may develop. The term often refers to those practices used to promote or induce asepsis in an operative field of surgery or medicine to prevent infection.

Antoine Béchamp French scientist

Pierre Jacques Antoine Béchamp was a French scientist now best known for breakthroughs in applied organic chemistry and for a bitter rivalry with Louis Pasteur.

In microbiology, pleomorphism is the ability of some microorganisms to alter their morphology, biological functions or reproductive modes in response to environmental conditions. Pleomorphism has been observed in some members of the Deinococcaceae family of bacteria. The modern definition of pleomorphism in the context of bacteriology is based on variation of morphology or functional methods of the individual cell, rather than a heritable change of these characters as previously believed.

Günther Enderlein

Günther Enderlein was a German zoologist, entomologist, microbiologist, researcher, physician for 60 years, and later a manufacturer of pharmaceutical products. Enderlein received international renown for his insect research, and in Germany became famous due to his concept of the pleomorphism of microorganisms and his hypotheses about the origins of cancer, based on the work of other scientists. His hypotheses about pleomorphism and cancer have now been disproved by science and have only some historical importance today. Some of his concepts, however, are still popular in alternative medicine. A blood test is named after him: dark field microscopy according to Enderlein.

Bacteria Domain of micro-organisms

Bacteria are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised and there are many species that cannot be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology.

Medical microbiology Branch of medical science concerned with the prevention, diagnosis and treatment of infectious diseases

Medical microbiology, the large subset of microbiology that is applied to medicine, is a branch of medical science concerned with the prevention, diagnosis and treatment of infectious diseases. In addition, this field of science studies various clinical applications of microbes for the improvement of health. There are four kinds of microorganisms that cause infectious disease: bacteria, fungi, parasites and viruses, and one type of infectious protein called prion.

Gerald Domingue is an American medical researcher and academic who served as Professor of Urology, Microbiology and Immunology in the Tulane University School of Medicine and Graduate School for thirty years and also as Director of Research in Urology. He is currently retired and resides in Zurich, Switzerland, where he is engaged in painting and creative writing. At retirement he was honored with the title of Professor Emeritus at Tulane (1967–1997). Prior to Tulane, he served on the faculty of St. Louis University ; was a lecturer at Washington University and director of clinical microbiology in St. Louis City Hospital, St. Louis, Missouri.

Microbiology Study of microscopic organisms

Microbiology is the scientific study of microorganisms, those being unicellular, multicellular, or acellular. Microbiology encompasses numerous sub-disciplines including virology, bacteriology, protistology, mycology, immunology and parasitology.

The French Louis Pasteur (1822–1895) and German Robert Koch (1843–1910) are the two greatest figures in medical microbiology and in establishing acceptance of the germ theory of disease. In 1882, fueled by national rivalry and a language barrier, the tension between Pasteur and the younger Koch erupted into an acute conflict.

Branches of microbiology

The branches of microbiology can be classified into pure and applied sciences. Microbiology can be also classified based on taxonomy, in the cases of bacteriology, mycology, protozoology, and phycology. There is considerable overlap between the specific branches of microbiology with each other and with other disciplines, and certain aspects of these branches can extend beyond the traditional scope of microbiology In general the field of microbiology can be divided in the more fundamental branch and the applied microbiology (biotechnology). In the more fundamental field the organisms are studied as the subject itself on a deeper (theoretical) level. Applied microbiology refers to the fields where the micro-organisms are applied in certain processes such as brewing or fermentation. The organisms itself are often not studied as such, but applied to sustain certain processes.


  1. Wassenaar, T. M. "Bacteriology: the study of bacteria". Archived from the original on 24 July 2011. Retrieved 18 June 2011.
  2. MacNeal, Ward J.; Williams, Herbert Upham (1914). Pathogenic micro-organisms; a text-book of microbiology for physicians and students of medicine. P. Blakiston's Sons. pp.  1. Retrieved 18 June 2011.
  3. Poindexter, Jeanne Stove (30 November 1986). Methods and special applications in bacterial ecology. Springer. p. 87. ISBN   978-0-306-42346-8 . Retrieved 18 June 2011.
  4. "Bacteriologist: Job Description, Duties and Salary". Retrieved 2017-04-03.
  5. "Act 841 of 2003" (PDF). By which the exercise of the profession is regulated bacteriologist, // the code of bioethics and other provisions are issued (in Spanish). Ministry of Education. Retrieved 15 May 2014.
  6. Wheelis 2008.
  7. Pommerville 2014, p. 7.
  8. Ehrenberg CG (1828). Symbolae Physioe. Animalia evertebrata. Berlin: Decas prima.
  9. Breed RS, Conn HJ (May 1936). "The Status of the Generic Term Bacterium Ehrenberg 1828". Journal of Bacteriology. 31 (5): 517–18. doi:10.1128/jb.31.5.517-518.1936. PMC   543738 . PMID   16559906.
  10. Ehrenberg CG (1835). Dritter Beitrag zur Erkenntniss grosser Organisation in der Richtung des kleinsten Raumes[Third contribution to the knowledge of great organization in the direction of the smallest space] (in German). Berlin: Physikalische Abhandlungen der Koeniglichen Akademie der Wissenschaften. pp. 143–336.
  11. "Pasteur's Papers on the Germ Theory". LSU Law Center's Medical and Public Health Law Site, Historic Public Health Articles. Archived from the original on 18 December 2006. Retrieved 23 November 2006.
  12. ‘Wash your hands’ was once controversial medical advice , National Geographic.
  13. Lakhtakia, R. (February 2014). "The Legacy of Robert Koch". Sultan Qaboos University Medical Journal. 14 (1): e37–41. PMC   3916274 . PMID   24516751.
  14. 1 2 3 Kreuder‐Sonnen, Katharina (2016). "History of Bacteriology". eLS. Wiley. pp. 1–11. doi:10.1002/9780470015902.a0003073.pub2. ISBN   9780470015902.
  15. 1 2 3 Baron, S. (1996). "Introduction to Bacteriology". In Baron, S. (ed.). Medical Microbiology (4th ed.). University of Texas Medical Branch at Galveston. ISBN   0-9631172-1-1. PMID   21413299. NBK8120.
  16. 1 2 3 "Bacteriology". Encyclopædia Britannica. Encyclopædia Britannica, Inc. 7 September 2010. Retrieved 22 November 2017.
  17. "The Nobel Prize in Physiology or Medicine 1905". Archived from the original on 10 December 2006. Retrieved 22 November 2006.
  18. O'Brien SJ, Goedert JJ (October 1996). "HIV causes AIDS: Koch's postulates fulfilled". Current Opinion in Immunology. 8 (5): 613–18. doi:10.1016/S0952-7915(96)80075-6. PMID   8902385.
  19. Chung K. "Ferdinand Julius Cohn (1828–1898): Pioneer of Bacteriology" (PDF). Department of Microbiology and Molecular Cell Sciences, The University of Memphis. Archived (PDF) from the original on 27 July 2011.
  20. Drews, Gerhart (1999). "Ferdinand Cohn, a founder of modern microbiology" (PDF). ASM News. 65 (8): 547–52. Archived from the original (PDF) on 13 July 2017.
  21. Thurston AJ (December 2000). "Of blood, inflammation and gunshot wounds: the history of the control of sepsis". The Australian and New Zealand Journal of Surgery. 70 (12): 855–61. doi:10.1046/j.1440-1622.2000.01983.x. PMID   11167573.
  22. Schwartz RS (March 2004). "Paul Ehrlich's magic bullets". The New England Journal of Medicine. 350 (11): 1079–80. doi:10.1056/NEJMp048021. PMID   15014180.
  23. "Biography of Paul Ehrlich". Archived from the original on 28 November 2006. Retrieved 26 November 2006.
  24. Woese CR, Fox GE (November 1977). "Phylogenetic structure of the prokaryotic domain: the primary kingdoms". Proceedings of the National Academy of Sciences of the United States of America. 74 (11): 5088–90. Bibcode:1977PNAS...74.5088W. doi: 10.1073/pnas.74.11.5088 . PMC   432104 . PMID   270744.
  25. Hall 2008, p. 145.


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