Propulsion, bacterial

Two examples where actin polymerization is observed in eukaryotes are in the bacterial pathogens Listeria monocytogenes and Shigella flexneri. The motion that the eukaryote pathogens exhibit is the actin based motility in the cytoplasm of their host. Actin polymerization is known to occur via an insertion polymerization mechanism. The movement is a result of site-directed tread-milling of the actin filaments. This type of movement is classified as a propulsive type motion. The driving force for actin pol)unerization as well as the next motor is the conversion of adenosine triphosphate (ATP) to adenosine diphosphate (ADP). ... 

Loperamide is a narcotic agonist acting on opioid JL receptors. Loperamide has mild antisecretory effects but its primary effects are to increase segmental intestinal contractions and slow the propulsion of intestinal contents (Ruppin 1987). Loperamide has been associated with reduction in diarrhea in many clinical studies in humans but has minimal impact on the patient s fluid and electrolyte balance because the secreted fluid remains in the bowel lumen. Loperamide can have dose-dependent CNS depressant effects. Loperamide also has been shown to promote intestinal bacterial overgrowth because of promoting the retention of fluid within bowel segments (Duval-Iflah et al 1999), which may favor the proliferation of enteropathogenic bacteria. 

A new problem that arises in the post-metamorphic, nursery stage is the collision of the juveniles with tank or net walls. This is due to the fish s remarkable propulsive power created by a fully formed caudal fin, whilst lacking the adult braking and steering capability due to the pectoral and abdominal fins not being as well developed (Normile, 2009). Such collisions may be instantly fatal due to a broken vertebral colunrn, or caused by secondary bacterial infections due to the skin abrasions. Many of these... 

NASA s Jet Propulsion Laboratory (JPL) developed a bacterial spore-detection system for Mars-bound spacecraft that can also recognize anthrax and other harmful, spore-forming bacteria on Earth and alert people of the impending danger. 

This model predicted that the bacterial velocity should depend on its diffusion coefficient, and thereby on its size. However, experiments showed that the velocity did not depend on the cell size, so the model was modified to allow thermal fluctuations of the actin filament tips [36], This resolved the size independence issue but the model ran afoul of another observation the actin tail appeared to be attached to the surface of the cell [30,37,38]. This problem was resolved by a further generalization of the model. The tethered ratchet model assumed that the filaments are initiated while attached to the bacterial surface, but subsequently detach and become working filaments as in the elastic ratchet model (Figure 3(a), [19]). The attached fibers are in tension and resist the forward progress of the bacterium. At the same time, the dissociated fibers are in compression, and generate the force of propulsion, each filament developing a force of a few pN. 

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