Strain (biology) in the context of "Animal testing on rodents"

Cholera (/ˈkɒlərə/) 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 lasting a few days. Vomiting and muscle cramps may also occur. Diarrhea can be so severe that it leads within hours to severe dehydration and electrolyte imbalance. This can in turn result in sunken eyes, cold or cyanotic skin, decreased skin elasticity, wrinkling of the hands and feet, and, in severe cases, death. Symptoms start two hours to five days after exposure.

Cholera is caused by a number of types of Vibrio cholerae, with some types producing more severe disease than others. It is spread mostly by unsafe water and unsafe food that has been contaminated with human feces containing the bacteria. Undercooked shellfish is a common source. Humans are the only known host for the bacteria. Risk factors for the disease include poor sanitation, insufficient clean drinking water, and poverty. Cholera can be diagnosed by a stool test, or a rapid dipstick test, although the dipstick test is less accurate.

Escherichia coli (/ˌɛʃəˈrɪkiə ˈkoʊlaɪ/ ESH-ə-RIK-ee-ə KOH-lye) is a gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms. Most E. coli strains are part of the normal microbiota of the gut, where they constitute about 0.1%, along with other facultative anaerobes. These bacteria are mostly harmless or even beneficial to humans. For example, some strains of E. coli benefit their hosts by producing vitamin K₂ or by preventing the colonization of the intestine by harmful pathogenic bacteria. These mutually beneficial relationships between E. coli and humans are a type of mutualistic biological relationship—where both the humans and the E. coli are benefitting each other. E. coli is expelled into the environment within fecal matter. The bacterium grows massively in fresh fecal matter under aerobic conditions for three days, but its numbers decline slowly afterwards.

Some serotypes, such as EPEC and ETEC, are pathogenic, causing serious food poisoning in their hosts. Fecal–oral transmission is the major route through which pathogenic strains of the bacterium cause disease. This transmission method is occasionally responsible for food contamination incidents that prompt product recalls. Cells are able to survive outside the body for a limited amount of time, which makes them potential indicator organisms to test environmental samples for fecal contamination. A growing body of research, though, has examined environmentally persistent E. coli which can survive for many days and grow outside a host.

In biological taxonomy, race is an informal rank in the taxonomic hierarchy for which various definitions exist. Sometimes it is used to denote a level below that of subspecies, while at other times it is used as a synonym for subspecies. It has been used as a higher rank than strain, with several strains making up one race. Races may be genetically distinct populations of individuals within the same species, or they may be defined in other ways, e.g. geographically, or physiologically. Genetic isolation between races is not complete, but genetic differences may have accumulated that are not (yet) sufficient to separate species.

The term is recognized by some, but not governed by any of the formal codes of biological nomenclature. Taxonomic units below the level of subspecies are not typically applied to animals.

In microbiology, isolation is the technique of separating one strain from a mixed population of living microorganisms. This allows identification of microorganisms in a sample taken from the environment, such as water or soil, or from a person or animal. Laboratory techniques for isolating bacteria and parasites were developed during the 19th century, and for viruses during the 20th century.

Baker's yeast is the common name for the strains of yeast commonly used in baking bread and other bakery products, serving as a leavening agent which causes the bread to rise (expand and become lighter and softer) by converting the fermentable sugars present in the dough into carbon dioxide and ethanol. Baker's yeast is of the species Saccharomyces cerevisiae, and is the same species (but a different strain) as the kind commonly used in alcoholic fermentation, which is called brewer's yeast or the deactivated form nutritional yeast. Baker's yeast is also a single-cell microorganism found on and around the human body.

The use of steamed or boiled potatoes, water from potato boiling, or sugar in a bread dough provides food for the growth of yeasts; however, too much sugar will dehydrate them. Yeast growth is inhibited by both salt and sugar, but more so by salt than sugar. Some sources say fats, such as butter and eggs, slow down yeast growth; others say the effect of fat on dough remains unclear, presenting evidence that small amounts of fat are beneficial for baked bread volume.

Allogamy or cross-fertilization is thefertilization of an ovum from one individual with the spermatozoa of another. By contrast, autogamy is the term used for self-fertilization. In humans, the fertilization event is an instance of allogamy. Self-fertilization occurs in hermaphroditic organisms where the two gametes fused in fertilization come from the same individual. This is common in plants (see Sexual reproduction in plants) and certain protozoans.

In plants, allogamy is used specifically to mean the use of pollen from one plant to fertilize the flower of another plant and usually synonymous with the term "cross-fertilization" or "cross-pollination" (outcrossing). The latter term can be used more specifically to mean pollen exchange between different plant strains or even different plant species (where the term cross-hybridization can be used) rather than simply between different individuals.

Escherichia coli (/ˌɛʃəˈrɪkiə ˈkoʊlaɪ/ ESH-ə-RIK-ee-ə KOH-ly; commonly abbreviated E. coli) is a gram-negative, rod-shaped bacterium that is commonly found in the lower intestine of warm-blooded organisms (endotherms). Most E. coli strains are harmless, but pathogenic varieties cause serious food poisoning, septic shock, meningitis, or urinary tract infections in humans. Unlike normal flora E. coli, the pathogenic varieties produce toxins and other virulence factors that enable them to reside in parts of the body normally not inhabited by E. coli, and to damage host cells. These pathogenic traits are encoded by virulence genes carried only by the pathogens.

Bacillus thuringiensis (or Bt) is a gram-positive, soil-dwelling bacterium, and is the most commonly used biological pesticide worldwide. B. thuringiensis also occurs naturally in the gut of caterpillars of various types of moths and butterflies, as well as on leaf surfaces, aquatic environments, animal feces, insect-rich environments, flour mills and grain-storage facilities. It has also been observed to parasitize moths such as Cadra calidella—in laboratory experiments working with C. calidella, many of the moths were diseased due to this parasite.

During sporulation, many Bt strains produce crystal proteins (proteinaceous inclusions), called delta endotoxins, that have insecticidal action. This has led to their use as insecticides, and more recently to genetically modified crops using Bt genes, such as Bt corn. Many crystal-producing Bt strains, though, do not have insecticidal properties. Bacillus thuringiensis israelensis (Bti) was discovered in 1976 by Israeli settler researchers Yoel Margalith and B. Goldberg in the Negev Desert of occupied Palestine. While investigating mosquito breeding sites in the region, they isolated a bacterial strain from a stagnant pond that exhibited potent larvicidal activity against various mosquito species, including Anopheles, Culex, and Aedes. This subspecies, israelensis, is now commonly used for the biological control of mosquitoes and fungus gnats due to its effectiveness and environmental safety.

Laboratory rats or lab rats are strains of the rat subspecies Rattus norvegicus domestica (Domestic Norwegian rat) which are bred and kept for scientific research. While less commonly used for research than laboratory mice, rats have served as an important animal model for research in psychology and biomedical science, and "lab rat" is commonly used as an idiom for a test subject.