Bacteriology is the branch and specialty of

biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...

that studies the

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

ecology Ecology () is the study of the relationships between living organisms, including humans, and their physical environment. Ecology considers organisms at the individual, population, community, ecosystem, and biosphere level. Ecology overlaps wi ...

genetics Genetics is the study of genes, genetic variation, and heredity in organisms.Hartl D, Jones E (2005) It is an important branch in biology because heredity is vital to organisms' evolution. Gregor Mendel, a Moravian Augustinian friar wor ...

and

biochemistry Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...

bacteria Bacteria (; singular: bacterium) 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 ...

as well as many other aspects related to them. This subdivision of

microbiology Microbiology () is the scientific study of microorganisms, those being unicellular (single cell), multicellular (cell colony), or acellular (lacking cells). Microbiology encompasses numerous sub-disciplines including virology, bacteriology, prot ...

involves the identification, classification, and characterization of bacterial species. Because of the similarity of thinking and working with

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s other than bacteria, such as

protozoa Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

, and

virus A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Since Dmitri Ivanovsky's 1 ...

es, there has been a tendency for the field of bacteriology to extend as microbiology. The terms were formerly often used interchangeably. However, bacteriology can be classified as a distinct science.

Overview

Definition

Bacteriology is the study of bacteria and their relation to medicine. Bacteriology evolved from physicians needing to apply the

germ theory 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 be seen without magnification, invade ...

to address the concerns relating to disease spreading in hospitals the 19th century. Identification and characterizing of bacteria being associated to diseases led to advances in pathogenic bacteriology.

Koch's postulates Koch's postulates ( )"Koch"
''

diphtheria toxoid Diphtheria vaccine is a toxoid vaccine against diphtheria, an illness caused by ''Corynebacterium diphtheriae''. Its use has resulted in a more than 90% decrease in number of cases globally between 1980 and 2000. The first dose is recommended a ...

and

tetanus toxoid Tetanus vaccine, also known as tetanus toxoid (TT), is a toxoid vaccine used to prevent tetanus. During childhood, five doses are recommended, with a sixth given during adolescence. After three doses, almost everyone is initially immune, but a ...

. Bacteriology can be studied and applied in many sub-fields relating to

agriculture Agriculture or farming is the practice 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 ...

marine biology Marine biology is the scientific study of the biology of marine life, organisms in the sea. Given that in biology many phyla, families and genera have some species that live in the sea and others that live on land, marine biology classifies s ...

water pollution Water pollution (or aquatic pollution) is the contamination of water bodies, usually as a result of human activities, so that it negatively affects its uses. Water bodies include lakes, rivers, oceans, aquifers, reservoirs and groundwater. Water ...

bacterial genetics Bacterial genetics is the subfield of genetics devoted to the study of bacterial genes. Bacterial genetics are subtly different from eukaryotic genetics, however bacteria still serve as a good model for animal genetic studies. One of the major dis ...

veterinary medicine Veterinary medicine is the branch of medicine that deals with the prevention, management, diagnosis, and treatment of disease, disorder, and injury in animals. Along with this, it deals with animal rearing, husbandry, breeding, research on nutri ...

biotechnology Biotechnology is the integration of natural sciences and engineering sciences in order to achieve the application of organisms, cells, parts thereof and molecular analogues for products and services. The term ''biotechnology'' was first used b ...

and others.

Bacteriologists

bacteriologist A bacteriologist is a microbiologist, or similarly trained professional, in bacteriology -- a subdivision of microbiology that studies bacteria, typically Pathogenic bacteria, pathogenic ones. Bacteriologists are interested in studying and learnin ...

is a

microbiologist A microbiologist (from Ancient Greek, Greek ) is a scientist who studies microscopic life forms and processes. This includes study of the growth, interactions and characteristics of Microorganism, microscopic organisms such as bacteria, algae, f ...

or other trained professional in bacteriology. Bacteriologists are interested in studying and learning about bacteria, as well as using their skills in clinical settings. This includes investigating properties of bacteria such as morphology, ecology, genetics and biochemistry, phylogenetics, genomics and many other areas related to bacteria like disease diagnostic testing. They can also work as medical scientists, veterinary scientists, or diagnostic technicians in locations like clinics, blood banks, hospitals, laboratories and animal hospitals. Bacteriologists working in public health or biomedical research help develop vaccines for public use.

Culturing bacteria

The growth of bacteria in laboratory cultures is the mainstay method used by bacteriologists. Both solid and liquid culture media are used. Solid culture medium is usually

nutrient agar Nutrient agar is a general purpose liquid medium supporting growth of a wide range of non-fastidious organisms. It typically contains ( mass/volume): * 0.5% peptone - this provides organic nitrogen * 0.3% beef extract/yeast extract - the wate ...

in a

petri dish A Petri dish (alternatively known as a Petri plate or cell-culture dish) is a shallow transparent lidded dish that biologists use to hold growth medium in which cells can be cultured,R. C. Dubey (2014): ''A Textbook Of Biotechnology For Class- ...

. The constituents of the nutrient agar vary according to the bacteria under investigation. For growing the bacterium ''

Haemophilus influenzae ''Haemophilus influenzae'' (formerly called Pfeiffer's bacillus or ''Bacillus influenzae'') is a Gram-negative, non-motile, coccobacillary, facultatively anaerobic, capnophilic pathogenic bacterium of the family Pasteurellaceae. The bacteria ...

'', for example, which is dependent on

hemin Hemin (haemin; ferric chloride heme) is an iron-containing porphyrin with chlorine that can be formed from a heme group, such as heme B found in the hemoglobin of human blood. Chemistry Hemin is protoporphyrin IX containing a ferric iron (Fe3 ...

and

nicotinamide adenine dinucleotide Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an aden ...

for its growth, blood (usually from a sheep or a horse) is added to the medium. When growing bacteria that are found in the intestines of mammals, such as

salmonella ''Salmonella'' is a genus of rod-shaped (bacillus) Gram-negative bacteria of the family Enterobacteriaceae. The two species of ''Salmonella'' are ''Salmonella enterica'' and ''Salmonella bongori''. ''S. enterica'' is the type species and is fur ...

XLD agar Xylose Lysine Deoxycholate agar (XLD agar) is a selective growth medium used in the isolation of ''Salmonella'' and ''Shigella'' species from clinical samples and from food. The agar was developed by Welton Taylor in 1965. It has a pH of approxi ...

which contains, among other ingredients

deoxycholic acid Deoxycholic acid is a bile acid. Deoxycholic acid is one of the secondary bile acids, which are metabolic byproducts of intestinal bacteria. The two primary bile acids secreted by the liver are cholic acid and chenodeoxycholic acid. Bacteria met ...

is used.

History

Bacteria were first observed by the Dutch microscopist

Antonie van Leeuwenhoek Antonie Philips van Leeuwenhoek ( ; ; 24 October 1632 – 26 August 1723) was a Dutch microbiologist and microscopist in the Golden Age of Dutch science and technology. A largely self-taught man in science, he is commonly known as " the ...

in 1676, using a single-lens

microscope A microscope () is a laboratory instrument used to examine objects that are too small to be seen by the naked eye. Microscopy is the science of investigating small objects and structures using a microscope. Microscopic means being invisibl ...

of his own design. He then published his observations in a series of letters to the

Royal Society of London The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...

. His observations also included protozoans, which he called

animalcule Animalcule ('little animal', from Latin ''animal'' + the diminutive suffix ''-culum'') is an old term for microscopic organisms that included bacteria, protozoans, and very small animals. The word was invented by 17th-century Dutch scientist An ...

s. The German

Ferdinand Cohn Ferdinand Julius Cohn (24 January 1828 – 25 June 1898) was a German biologist. He is one of the founders of modern bacteriology and microbiology. Ferdinand J. Cohn was born in the Jewish quarter of Breslau in the Kingdom of Prussia, Prussia ...

began studying bacteria in 1870 and is also said to be a founder of bacteriology, as he was the first to classify bacteria based on their

Louis Pasteur Louis Pasteur (, ; 27 December 1822 – 28 September 1895) was a French chemist and microbiologist renowned for his discoveries of the principles of vaccination, microbial fermentation and pasteurization, the latter of which was named afte ...

demonstrated in 1859 that microorganisms cause the

fermentation Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen. In food ...

process, and that this growth is not due to

spontaneous generation Spontaneous generation is a superseded scientific theory that held that living creatures could arise from nonliving matter and that such processes were commonplace and regular. It was hypothesized that certain forms, such as fleas, could arise fr ...

(

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...

s and molds, commonly associated with fermentation, are not bacteria, but rather

). Along with his contemporary

Robert Koch Heinrich Hermann Robert Koch ( , ; 11 December 1843 – 27 May 1910) was a German physician and microbiologist. As the discoverer of the specific causative agents of deadly infectious diseases including tuberculosis, cholera (though the Vibrio ...

, Pasteur was an early advocate of the

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 be seen without magnification, invade h ...

. Between 1880 and 1881 Pasteur produced two successful

vaccination Vaccination is the administration of a vaccine to help the immune system develop immunity from a disease. Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organism. In stimulating ...

s for animals against diseases caused by bacteria. The importance of bacteria was recognized as it led to a study of disease prevention and treatment of diseases by vaccines. Pasteur's research led to

Ignaz Semmelweis Ignaz Philipp Semmelweis (; hu, Semmelweis Ignác Fülöp ; 1 July 1818 – 13 August 1865) was a Hungarian physician and scientist, who was an early pioneer of antiseptic procedures. Described as the "saviour of mothers", he discovered that t ...

and

Joseph Lister Joseph Lister, 1st Baron Lister, (5 April 182710 February 1912) was a British surgeon, medical scientist, experimental pathologist and a pioneer of antiseptic surgery and preventative medicine. Joseph Lister revolutionised the craft of s ...

researching the importance of sanitized hands in medical work. In the 1840s, Semmelweis' observations and ideas surrounding sanitary techniques were rejected and his book on the topic condemned by the medical community due to its conflict with the prevailing theory and practice of

humorism Humorism, the humoral theory, or humoralism, was a system of medicine detailing a supposed makeup and workings of the human body, adopted by Ancient Greek and Roman physicians and philosophers. Humorism began to fall out of favor in the 1850s ...

at the time. After Lister's publications, which supported hand washing and sanitation with germ theory, doctors started sanitizing their hands in the 1870s; mandatory handwashing was not incorporated into common health practice until as late as the 1980s. The discovery of the connection of microorganisms to disease came later in the nineteenth century, when Italian anatomist

Filippo Pacini Filippo Pacini (25 May 1812 – 9 July 1883) was an Italian anatomist, posthumously famous for isolating the cholera bacterium ''Vibrio cholerae'' in 1854, well before Robert Koch's more widely accepted discoveries 30 years later. Pacini was born ...

isolated the

cholera Cholera is an infection of the small intestine by some strains of the bacterium ''Vibrio cholerae''. Symptoms may range from none, to mild, to severe. The classic symptom is large amounts of watery diarrhea that lasts a few days. Vomiting and ...

bacterium ''

Vibrio cholerae ''Vibrio cholerae'' is a species of Gram-negative, facultative anaerobe and comma-shaped bacteria. The bacteria naturally live in brackish or saltwater where they attach themselves easily to the chitin-containing shells of crabs, shrimps, and oth ...

'' in 1854 in Florence during the Asiatic Cholera Pandemic of 1846-63 and clearly linked the presence of the bacterium in the intestinal mucosa of dead cholera patients to the disease. Although Pacini's work was available to the international scientific community via French and English translations, the discovery of the cholera-causing agent is often attributed to the German physician

who rediscovered it in 1884. Koch is credited for introducing the science of microorganisms including bacteria to the medical field. Koch, a pioneer in medical microbiology, worked on

anthrax Anthrax is an infection caused by the bacterium ''Bacillus anthracis''. It can occur in four forms: skin, lungs, intestinal, and injection. Symptom onset occurs between one day and more than two months after the infection is contracted. The sk ...

and

tuberculosis Tuberculosis (TB) is an infectious disease usually caused by '' Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can also affect other parts of the body. Most infections show no symptoms, in ...

. In his research into tuberculosis Koch finally proved the germ theory, for which he received a

Nobel Prize The Nobel Prizes ( ; sv, Nobelpriset ; no, Nobelprisen ) are five separate prizes that, according to Alfred Nobel's will of 1895, are awarded to "those who, during the preceding year, have conferred the greatest benefit to humankind." Alfr ...

in 1905. In

Koch's postulates Koch's postulates ( )"Koch"
''

disease A disease is a particular abnormal condition that negatively affects the structure or function of all or part of an organism, and that is not immediately due to any external injury. Diseases are often known to be medical conditions that a ...

, and these postulates are still used today. Both Koch and Pasteur played a role in improving antisepsis in medical treatment. In 1870-1885 the modern methods of bacteriology technique were introduced by the use of

stains A stain is an unwanted localized discoloration, often in fabrics or textiles. Stain(s) or The Stain(s) may also refer to: Color * Stain (heraldry), a non-standard tincture * Staining, in biology, a technique used to highlight contrast in samples ...

, and by the method of separating mixtures of organisms on plates of nutrient media. Though it had been known since the nineteenth century that bacteria are a cause of many diseases, no effective

antibacterial An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention of ...

treatments were available until the 20th century. In 1910,

Paul Ehrlich Paul Ehrlich (; 14 March 1854 – 20 August 1915) was a Nobel Prize-winning German physician and scientist who worked in the fields of hematology, immunology, and antimicrobial chemotherapy. Among his foremost achievements were finding a cure ...

developed the first antibiotic, by changing dyes that selectively stained ''

Treponema pallidum ''Treponema pallidum'', formerly known as ''Spirochaeta pallida'', is a spirochaete bacterium with various subspecies that cause the diseases syphilis, bejel (also known as endemic syphilis), and yaws. It is transmitted only among humans. It is ...

''—the

spirochaete A spirochaete () or spirochete is a member of the phylum Spirochaetota (), (synonym Spirochaetes) which contains distinctive diderm (double-membrane) gram-negative bacteria, most of which have long, helically coiled (corkscrew-shaped or s ...

that causes

syphilis Syphilis () is a sexually transmitted infection caused by the bacterium ''Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, an ...

—into compounds that selectively killed the pathogen. Ehrlich was awarded a 1908 Nobel Prize for his work on

immunology Immunology is a branch of medicineImmunology for Medical Students, Roderick Nairn, Matthew Helbert, Mosby, 2007 and biology that covers the medical study of immune systems in humans, animals, plants and sapient species. In such we can see there ...

, and pioneered the use of stains to detect and identify bacteria, with his work being the basis of the

Gram stain In microbiology and bacteriology, Gram stain (Gram staining or Gram's method), is a method of staining used to classify bacterial species into two large groups: gram-positive bacteria and gram-negative bacteria. The name comes from the Danish ...

and the

Ziehl–Neelsen 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 modif ...

. A major step forward in the study of bacteria came in 1977 when

Carl Woese Carl Richard Woese (; July 15, 1928 – December 30, 2012) was an American microbiologist and biophysicist. Woese is famous for defining the Archaea (a new domain of life) in 1977 through a pioneering phylogenetic taxonomy of 16S ribosomal RNA, ...

recognised that

archaea Archaea ( ; singular archaeon ) is a domain of single-celled organisms. These microorganisms lack cell nuclei and are therefore prokaryotes. Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebac ...

have a separate line of evolutionary descent from bacteria. This new

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

came from the

sequencing In genetics and biochemistry, sequencing means to determine the primary structure (sometimes incorrectly called the primary sequence) of an unbranched biopolymer. Sequencing results in a symbolic linear depiction known as a sequence which succ ...

16S ribosomal RNA 16 S ribosomal RNA (or 16 S rRNA) is the RNA component of the 30S subunit of a prokaryotic ribosome (SSU rRNA). It binds to the Shine-Dalgarno sequence and provides most of the SSU structure. The genes coding for it are referred to as 16S rRNA ...

and divided prokaryotes into two evolutionary domains as part of the

three-domain system The three-domain system is a biological classification introduced by Carl Woese, Otto Kandler, and Mark Wheelis in 1990 that divides cellular life forms into three domains, namely Archaea, Bacteria, and Eukaryota or Eukarya. The key difference fr ...

References

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