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Motility
Motility is the ability of an organism to move independently, using metabolic energy. Definitions Motility, the ability of an organism to move independently, using metabolic energy, can be contrasted with sessility, the state of organisms that do not possess a means of self-locomotion and are normally immobile. Motility differs from mobility, the ability of an object to be moved. The term vagility encompasses both motility and mobility; sessile organisms including plants and fungi often have vagile parts such as fruits, seeds, or spores which may be dispersed by other agents such as wind, water, or other organisms. Motility is genetically determined, but may be affected by environmental factors such as toxins. The nervous system and musculoskeletal system provide the majority of mammalian motility. In addition to animal locomotion, most animals are motile, though some are vagile, described as having passive locomotion. Many bacteria and other microorganisms, and multicel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gliding Motility
Gliding motility is a type of translocation used by microorganisms that is independent of propulsive structures such as flagella, pili, and fimbriae. Gliding allows microorganisms to travel along the surface of low aqueous films. The mechanisms of this motility are only partially known. Twitching motility also allows microorganisms to travel along a surface, but this type of movement is jerky and uses pili as its means of transport. Bacterial gliding is a type of gliding motility that can also use pili for propulsion. The speed of gliding varies between organisms, and the reversal of direction is seemingly regulated by some sort of internal clock. For example the apicomplexans are able to travel at fast rates between 1–10 µm/s. In contrast ''Myxococcus xanthus'' bacteria glide at a rate of 0.08 µm/s. Cell-invasion and gliding motility have TRAP (thrombospondin-related anonymous protein), a surface protein, as a common molecular basis that is both essential for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Twitching Motility
Twitching motility is a form of crawling bacterial motility used to move over surfaces. Twitching is mediated by the activity of hair-like filaments called type IV pili which extend from the cell's exterior, bind to surrounding solid substrates and retract, pulling the cell forwards in a manner similar to the action of a grappling hook. The name ''twitching motility'' is derived from the characteristic jerky and irregular motions of individual cells when viewed under the microscope. It has been observed in many bacterial species, but is most well studied in ''Pseudomonas aeruginosa'', ''Neisseria gonorrhoeae'' and '' Myxococcus xanthus''. Active movement mediated by the twitching system has been shown to be an important component of the pathogenic mechanisms of several species. Mechanisms Pilus structure The type IV pilus complex consists of both the pilus itself and the machinery required for its construction and motor activity. The pilus filament is largely composed of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flagellum
A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have from one to many flagella. A gram-negative bacterium ''Helicobacter pylori'' for example uses its multiple flagella to propel itself through the mucus lining to reach the stomach epithelium, where it may cause a gastric ulcer to develop. In some bacteria the flagellum can also function as a sensory organelle, being sensitive to wetness outside the cell. Across the three domains of Bacteria, Archaea, and Eukaryota the flagellum has a different structure, protein composition, and mechanism of propulsion but shares the same function of providing motility. The Latin word means "whip" to describe its lash-like swimming motion. The flagellum in archaea is called the archaellum to note its difference from the bacterial flagellum. Eukaryotic f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flagellar Motility
A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have from one to many flagella. A gram-negative bacterium ''Helicobacter pylori'' for example uses its multiple flagella to propel itself through the mucus lining to reach the stomach epithelium, where it may cause a gastric ulcer to develop. In some bacteria the flagellum can also function as a sensory organelle, being sensitive to wetness outside the cell. Across the three domains of Bacteria, Archaea, and Eukaryota the flagellum has a different structure, protein composition, and mechanism of propulsion but shares the same function of providing motility. The Latin word means "whip" to describe its lash-like swimming motion. The flagellum in archaea is called the archaellum to note its difference from the bacterial flagellum. Eukaryotic fl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Swarming Motility
Swarming motility is a rapid (2–10 μm/s) and coordinated translocation of a bacterial population across solid or semi-solid surfaces, and is an example of bacterial multicellularity and swarm behaviour. Swarming motility was first reported by Jorgen Henrichsen and has been mostly studied in genus ''Serratia'', '' Salmonella'', ''Aeromonas'', ''Bacillus'', '' Yersinia'', ''Pseudomonas'', ''Proteus'', ''Vibrio'' and ''Escherichia''. This multicellular behavior has been mostly observed in controlled laboratory conditions and relies on two critical elements: 1) the nutrient composition and 2) viscosity of culture medium (i.e. % agar). One particular feature of this type of motility is the formation of dendritic fractal-like patterns formed by migrating swarms moving away from an initial location. Although the majority of species can produce tendrils when swarming, some species like '' Proteus mirabilis'' do form concentric circles motif instead of dendritic patterns. Biosurfacta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amoeboid Movement
Amoeboid movement is the most typical mode of locomotion in adherent eukaryotic cells. It is a crawling-like type of movement accomplished by protrusion of cytoplasm of the cell involving the formation of pseudopodia ("false-feet") and posterior uropods. One or more pseudopodia may be produced at a time depending on the organism, but all amoeboid movement is characterized by the movement of organisms with an amorphous form that possess no set motility structures. Movement occurs when the cytoplasm slides and forms a pseudopodium in front to pull the cell forward. Some examples of organisms that exhibit this type of locomotion are amoebae (such as ''Amoeba proteus'' and '' Naegleria gruberi'',) and slime molds, as well as some cells in humans such as leukocytes. Sarcomas, or cancers arising from connective tissue cells, are particularly adept at amoeboid movement, thus leading to their high rate of metastasis. This type of movement has been linked to changes in action potential ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gastrointestinal Physiology
Gastrointestinal physiology is the branch of human physiology that addresses the physical function of the gastrointestinal (GI) tract. The function of the GI tract is to process ingested food by mechanical and chemical means, extract nutrients and excrete waste products. The GI tract is composed of the alimentary canal, that runs from the mouth to the anus, as well as the associated glands, chemicals, hormones, and enzymes that assist in digestion. The major processes that occur in the GI tract are: motility, secretion, regulation, digestion and circulation. The proper function and coordination of these processes are vital for maintaining good health by providing for the effective digestion and uptake of nutrients. Motility The gastrointestinal tract generates motility using smooth muscle subunits linked by gap junctions. These subunits fire spontaneously in either a tonic or a phasic fashion. Tonic contractions are those contractions that are maintained from several minutes up ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spermatozoa
A spermatozoon (; also spelled spermatozoön; ; ) is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote. (A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo.) Sperm cells contribute approximately half of the nuclear genetic information to the diploid offspring (excluding, in most cases, mitochondrial DNA). In mammals, the sex of the offspring is determined by the sperm cell: a spermatozoon bearing an X chromosome will lead to a female (XX) offspring, while one bearing a Y chromosome will lead to a male (XY) offspring. Sperm cells were first observed in Antonie van Leeuwenhoek's laboratory in 1677. Mammalian spermatozoon structure, function, and size Humans The human sperm cell is the reproductive cell in males and will only survive in warm environments; once it leaves the male body the sperm's survival likelihood is reduced and it may die, thereby ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pilus
A pilus (Latin for 'hair'; plural: ''pili'') is a hair-like appendage found on the surface of many bacteria and archaea. The terms ''pilus'' and '' fimbria'' (Latin for 'fringe'; plural: ''fimbriae'') can be used interchangeably, although some researchers reserve the term ''pilus'' for the appendage required for bacterial conjugation. All conjugative pili are primarily composed of pilin – fibrous proteins, which are oligomeric. Dozens of these structures can exist on the bacterial and archaeal surface. Some bacteria, viruses or bacteriophages attach to receptors on pili at the start of their reproductive cycle. Pili are antigenic. They are also fragile and constantly replaced, sometimes with pili of different composition, resulting in altered antigenicity. Specific host responses to old pili structures are not effective on the new structure. Recombination genes of pili code for variable (V) and constant (C) regions of the pili (similar to immunoglobulin diversity). As t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shigella
''Shigella'' is a genus of bacteria that is Gram-negative, facultative anaerobic, non-spore-forming, nonmotile, rod-shaped, and genetically closely related to '' E. coli''. The genus is named after Kiyoshi Shiga, who first discovered it in 1897. The causative agent of human shigellosis, ''Shigella'' causes disease in primates, but not in other mammals. It is only naturally found in humans and gorillas. During infection, it typically causes dysentery. ''Shigella'' is one of the leading bacterial causes of diarrhea worldwide, causing an estimated 80–165 million cases. The number of deaths it causes each year is estimated at between 74,000 and 600,000. It is one of the top four pathogens that cause moderate-to-severe diarrhea in African and South Asian children. Classification ''Shigella'' species are classified by three serogroups and one serotype: * Serogroup ''A'': '' S. dysenteriae'' (15 serotypes) * Serogroup ''B'': '' S. flexneri'' (9 serotypes) * Serogroup ''C'': ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Segmentation Contractions
Segmentation contractions (or movements) are a type of intestinal motility. Unlike peristalsis, which predominates in the esophagus, segmentation contractions occur in the large intestine and small intestine, while predominating in the latter. While peristalsis involves one-way motion in the caudal direction, segmentation contractions move chyme in both directions, which allows greater mixing with the secretions of the intestines. Segmentation involves contractions of the circular muscles in the digestive tract, while peristalsis involves rhythmic contractions of the longitudinal muscles in the gastrointestinal tract The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans a .... Unlike peristalsis, segmentation actually can slow progression of chyme through the system. External links * Anima ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
