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An agar plate streaked with microorganisms Agar plate with colonies.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.

Biology is the natural science that studies life and living organisms, including their physical structure, chemical processes, molecular interactions, physiological mechanisms, development and evolution. Despite the complexity of the science, there are certain unifying concepts that consolidate it into a single, coherent field. Biology recognizes the cell as the basic unit of life, genes as the basic unit of heredity, and evolution as the engine that propels the creation and extinction of species. Living organisms are open systems that survive by transforming energy and decreasing their local entropy to maintain a stable and vital condition defined as homeostasis.

Morphology (biology) In biology, the form and structure of organisms

Morphology is a branch of biology dealing with the study of the form and structure of organisms and their specific structural features.

Ecology Scientific study of the relationships between living organisms and their environment

Ecology is the branch of biology which studies the interactions among organisms and their environment. Objects of study include interactions of organisms that include biotic and abiotic components of their environment. Topics of interest include the biodiversity, distribution, biomass, and populations of organisms, as well as cooperation and competition within and between species. Ecosystems are dynamically interacting systems of organisms, the communities they make up, and the non-living components of their environment. Ecosystem processes, such as primary production, pedogenesis, nutrient cycling, and niche construction, regulate the flux of energy and matter through an environment. These processes are sustained by organisms with specific life history traits. Biodiversity means the varieties of species, genes, and ecosystems, enhances certain ecosystem services.



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.

Germ theory of disease

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 or even non-living pathogen that can cause disease, such as protists, fungi, 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.

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, but they have been controversially generalized to other diseases. These postulates were generated prior to understanding of modern concepts in microbial pathogenesis that cannot be examined using Koch's postulates, including viruses or asymptomatic carriers. They have largely been supplanted by other criteria such as the Bradford Hill criteria for infectious disease causality in modern public health.

Typhoid vaccines are vaccines that prevent typhoid fever. Several types are widely available: typhoid conjugate vaccine (TCV), Ty21a and Vi capsular polysaccharide vaccine (ViPS). They are about 30 to 70% effective for the first two years depending on the specific vaccine in question. The Vi-rEPA vaccine has been shown to be efficacious in children.


Statue of Koch in Berlin Statue of Robert Koch in Berlin.jpg
Statue of Koch in Berlin
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

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. He identified bacteria as the cause of infectious diseases and process of fermentation in diseases. French scientist 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. Bacteriology has developed and can be studied in agriculture, marine biology, water pollution, bacterial genetics and biotechnology. [4] [5] [6] [7]

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

Heinrich Hermann Robert Koch was a German physician and microbiologist. As one of the main founders of modern bacteriology, he identified the specific causative agents of tuberculosis, cholera, and anthrax and gave experimental support for the concept of infectious disease, which included experiments on humans and other animals. Koch created and improved laboratory technologies and techniques in the field of microbiology, and made key discoveries in public health. His research led to the creation of Koch's postulates, a series of four generalized principles linking specific microorganisms to specific diseases that remain today the "gold standard" in medical microbiology. For his research on tuberculosis, Koch received the Nobel Prize in Physiology or Medicine in 1905. The Robert Koch Institute is named in his honor.

Louis Pasteur French chemist and microbiologist

Louis Pasteur was a French biologist, microbiologist and chemist renowned for his discoveries of the principles of vaccination, microbial fermentation and pasteurization. He is remembered for his remarkable breakthroughs in the causes and prevention of diseases, and his discoveries have saved many lives ever since. He reduced mortality from puerperal fever, and created the first vaccines for rabies and anthrax.

Agriculture Cultivation of plants and animals to provide useful products

Agriculture is the science and art of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people to live in cities. The history of agriculture began thousands of years ago. After gathering wild grains beginning at least 105,000 years ago, nascent farmers began to plant them around 11,500 years ago. Pigs, sheep and cattle were domesticated over 10,000 years ago. Plants were independently cultivated in at least 11 regions of the world. Industrial agriculture based on large-scale monoculture in the twentieth century came to dominate agricultural output, though about 2 billion people still depended on subsistence agriculture into the twenty-first.

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Microorganism Microscopic living organism

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


A pilus is a hair-like appendage found on the surface of many bacteria and archaea. The terms pilus and fimbria can be used interchangeably, although some researchers reserve the term pilus for the appendage required for bacterial conjugation. All pili in the latter sense are primarily composed of pilin proteins, which are oligomeric.

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 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 made some of the greatest breakthroughs in modern medicine at the time, including pasteurization and vaccines for anthrax and rabies. The institute was founded on June 4, 1887, and inaugurated on November 14, 1888.

Bacterial capsule

The bacterial capsule is a very large structure of many bacteria. It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell. It is a well-organized layer, not easily washed off, and it can be the cause of various diseases.

Stanley Falkow American microbiologist

Stanley Falkow was an American microbiologist and a professor of microbiology and immunology at Stanford University School of Medicine. He discovered molecular mechanisms of infectious diseases, like antibiotic resistance and sounded the alarm for antibiotic-resistant bacteria. He championed the benefits of microorganisms. He formulated molecular Koch's postulates, which have guided the study of the microbial determinants of infectious diseases since the late 1980s.

In microbiology, pleomorphism(from greek πλέω- more, and -μορφή form) is the ability of some micro-organisms to alter their shape or size in response to environmental conditions. Pleomorphism has been observed in some members of the Deinococcaceae family. The modern definition of pleomorphism in the context of bacteriology is based on variation of size or shape of the cell, rather than a change of shape as previously believed.

Artificial induction of immunity is the artificial induction of immunity to specific diseases – making people immune to disease by means other than waiting for them to catch the disease. The purpose is to reduce the risk of death and suffering.

Medical microbiology medical specialty

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.

<i>Clostridium tetani</i> species of bacterium

Clostridium tetani is a common soil bacterium and the causative agent of tetanus. When growing in soil, C. tetani are rod-shaped and up to 2.5 micrometres long. However, when forming spores C. tetani becomes substantially enlarged at one end, resembling tennis rackets or drumsticks. C. tetani spores are extremely hardy and can be found globally in soil or in the gastrointestinal tract of animals. If inoculated into a wound, C. tetani can grow and produce a potent toxin, tetanospasmin, which interferes with motor neurons, causing tetanus. All mammals are susceptible to the disease. The toxin's action can be prevented with tetanus toxoid vaccines, which are often administered to children worldwide.

Pathogenic bacteria

Pathogenic bacteria are bacteria that can cause disease. This article deals with human pathogenic bacteria. Although most bacteria are harmless or often beneficial, some are pathogenic, with the number of species estimated as fewer than a hundred that are seen to cause infectious diseases in humans. By contrast, several thousand species exist in the human digestive system.

Vibrion may also refer to: the singular form of vibrio, a genus of anaerobic bacteria with a comma-like shape. Vibrion is an antiquated term for microorganisms, especially pathogenic ones; see Germ theory of disease. The term was specifically used in reference to motile microorganisms, and the name of the genus Vibrio derives from this term. The term is closely tied to the history of the study of cholera. It was used in biological literature between the late 19th century and the 1920s.

Microbiology Study of microscopic organisms

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

Philippe Sansonetti French microbiologist

Philippe J. Sansonetti is a microbiologist, Professor at the Pasteur Institute and the Collège de France in Paris. He is the Director of the Inserm Unit 786 and of the Institut Pasteur laboratory Pathogénie Microbienne Moléculaire.

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.

In biology, a pathogen, in the oldest and broadest sense, is anything that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ.

Wilhelm Kolle was a German bacteriologist and hygienist. He served as the second director of the Royal Institute for Experimental Therapy, succeeding its founder, the Nobel laureate Paul Ehrlich. He was also the original author, with Heinrich Hetsch, of the famous book Experimental Bacteriology, one of the most authoritative works in microbiology in the first half of the 20th century.

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. Ward J. MacNeal; Herbert Upham Williams (1914). Pathogenic micro-organisms; a text-book of microbiology for physicians and students of medicine. P. Blakiston's sons & co. pp. 1–. Retrieved 18 June 2011.
  3. Jeanne Stove Poindexter (30 November 1986). Methods and special applications in bacterial ecology. Springer. p. 87. ISBN   978-0-306-42346-8 . Retrieved 18 June 2011.
  4. Kreuder‐Sonnen, Katharina(Aug 2016) History of Bacteriology. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0003073.pub2]
  5. Kreuder‐Sonnen, Katharina(Aug 2016) History of Bacteriology. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0003073.pub2]
  6. Baron, Samuel. “Introduction to Bacteriology.” Medical Microbiology. 4th Edition., U.S. National Library of Medicine, 1 Jan. 1996, Retrieved 22 November 2017
  7. The Editors of Encyclopædia Britannica. “Bacteriology.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 7 Sept. 2010, Retrieved 22 November 2017

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