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The prokaryotic flagellum uses a rotary motor, and the eukaryotic flagellum uses a complex sliding filament system. Eukaryotic flagella are ATP-driven, while prokaryotic flagella can be ATP-driven (Archaea) or proton-driven (Bacteria). [11] The three types of flagella are bacterial, archaeal, and eukaryotic.
As such, the type three secretory system supports the hypothesis that the flagellum evolved from a simpler bacterial secretion system. However, the true relationship could be the reverse: recent phylogenetic research strongly suggests the type three secretory system evolved from the flagellum through a series of gene deletions. [7]
Some of the bacteria possessing a T3SS have flagella as well and are motile (Salmonella, for instance), and some do not (Shigella, for instance). Technically speaking, type III secretion is used both for secreting infection-related proteins and flagellar components.
Flagella in eukaryotes are supported by microtubules in a characteristic arrangement, with nine fused pairs surrounding two central singlets. These arise from a basal body. In some flagellates, flagella direct food into a cytostome or mouth, where food is ingested. Flagella role in classifying eukaryotes.
Model of the base of a bacterial flagellum, a true biological example of a freely rotating structure. The only known example of a biological "wheel" or "propeller"—a system capable of providing continuous propulsive torque about a fixed body—is the flagellum, a corkscrew-like tail used by single-celled prokaryotes for propulsion.
Eukaryotic flagella are complex cellular projections that lash back and forth, rather than in a circular motion. Prokaryotic flagella use a rotary motor, and the eukaryotic flagella use a complex sliding filament system. Eukaryotic flagella are ATP-driven, while prokaryotic flagella can be ATP-driven (archaea) or proton-driven (bacteria). [22]
Flagellins are a family of proteins present in flagellated bacteria [1] which arrange themselves in a hollow cylinder to form the filament in a bacterial flagellum. Flagellin has a mass on average of about 40,000 daltons. [2] [3] Flagellins are the principal component of bacterial flagella that have a crucial role in bacterial motility.
Perhaps the most recognizable extracellular bacterial cell structures are flagella. Flagella are whip-like structures protruding from the bacterial cell wall and are responsible for bacterial motility (movement). The arrangement of flagella about the bacterial cell is unique to the species observed. Common forms include: