Flagella


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flagella

[flə′jel·ə]
(biology)
Relatively long, whiplike, centriole-based locomotor organelles on some motile cells.

Flagella

 

cytoplasmic processes of a cell, characteristic of all flagellates and many bacteria, zoospores, and spermatozoa of all plants and animals.

Earlier, flagella were considered in contraposition to cilia. Electron-microscope investigations have shown the structural resemblance of these processes, which differ from one another only in number: a cell usually has one or several flagella and many cilia (up to several thousand). For this reason the terms “flagella” and “cilia” are often used as synonyms. The lengths of flagella vary greatly from cell to cell, and their diameters are each approximately 0.2 microns. Each flagellum has a shaft covered with a plasmic membrane (a continuation of the cell membrane) and consisting of a homogeneous substance, of which there are nine double fibrils along the periphery and two single fibrils in the center (thickness 250-600 A) with an electronically denser edge and a less dense central area; for this reason the fibrils are called microtubules. At the base of the flagellum is the basal body, a homologue of the centriole. Several forms of movement are distinguished in flagella: rotary, including spiral, motion; undulating motion, with wavelike movement from the free end to the base of the flagellum; and paddle-stroke motion. A similarity between the protein of flagella and the proteins of muscle has been discovered.

M. E. ASPIZ

References in periodicals archive ?
For these characteristics and for their curved, fluted, beaklike tip, the type 1 sensilla are also similar to the denticulate setae described in other decapod shrimp (Bauer and Caskey, 2006), which are much shorter and can be compared to the type 2 sensilla found in large numbers on both flagella. With their curved-beaked tip, the type 1 and type 2 sensilla could also be considered a variant of the long- and short-beaked sensilla of crayfish (Mellon, 2012).
FlaA is the most important constituent of the outer surface of flagella. This protein is recognized by the normal immune response system, such that the body's first line of defense would respond against the bacterium.
For examination and recording of the disintegration of sperm flagella by microtubule sliding, the 40x BM objective was usually used, while the 100x DL objective was for more precise measurement.
However, while both prokaryotic and eukaryotic flagella are used for swimming, they vary significantly in protein composition, structure, and mechanism of propulsion [110, 111].
Flagella, Gioli and other young designers attended a party hosted by Vogue Italia and French luxury giant Kering, owner of Gucci among other top brands.
In some bacteria, they interfere with iron metabolism, while in others they impair the expression of a gene called fliC, which is needed to produce the flagella bacteria use to swim and crawl along surfaces.
Note: The holotype is a moderately well preserved specimen with tips of both antennae (flagella contain 6 and 12 segments, respectively), one fore leg, tarsi behind basitarsus of one mid and one hind leg, and apices of ovipositor and sheath absent; mesosoma slightly deformed.
In 1954, Brisou and Prevot proposed the genus Acinetobacter to indicate that the bacteria were nonmotile because they lacked flagella. Acinetobacter are still generally described as nonmotile, but most isolates exhibit "twitching" motility.
Generally, bacterial signaling acts in the opposite way: Bacteria use flagella to swim into areas where they accumulate to high concentrations.
Pili and flagella; current research and future trends.