Nutritional changes may also cause bacterial filamentation. For example, if bacteria are deprived of the nucleobase thymine by starvation, this disrupts DNA synthesis and induces SOS-mediated filamentation.
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UV light damages bacterial DNA and induces filamentation via the SOS response.
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If bacteria are deprived of the nucleobase thymine by treatment with folic acid synthesis inhibitors (eg. trimethoprim), this also disrupts DNA synthesis and induces SOS-mediated filamentation. Direct obstruction of Z-ring formation by SulA and other FtsZ inhibitors (eg. berberine) induces filamentation too.
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Farnesol is used by the fungus Candida albicans as a quorum sensing molecule that inhibits filamentation.
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In this relate, filamentation could be not only a virulence, but also a resistance factor in these bacteria.
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However, in the situation of laser filamentation, the beam will quickly recollapse. This divergence and refocusing will continue indefinitely.
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Some peptidoglycan synthesis inhibitors (eg. cefuroxime, ceftazidime) induce filamentation by inhibiting the penicillin binding proteins (PBPs) responsible for crosslinking peptidoglycan at the septal wall (eg. PBP3 in E. coli and P. aeruginosa). Because the PBPs responsible for lateral wall synthesis are relatively unaffected by cefuroxime and ceftazidime, cell elongation proceeds without any cell division and filamentation is observed.
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A Bacillus cereus cell that has undergone filamentation following antibacterial treatment (upper electron micrograph; top right) and regularly sized cells of untreated B. cereus (lower electron micrograph) Filamentation is the anomalous growth of certain bacteria, such as Escherichia coli, in which cells continue to elongate but do not divide (no septa formation). The cells that result from elongation without division have multiple chromosomal copies. In the absence of antibiotics or other stressors, filamentation occurs at a low frequency in bacterial populations (4-8% short filaments and 0-5% long filaments in 1- to 8-hour cultures), the increased cell length protecting bacteria from protozoan predation and neutrophil phagocytosis by making ingestion of the cells more difficult. Filamentation is also a virulence factor thought to protect bacteria from antibiotics, and is associated with other aspects of bacterial virulence such as biofilm formation.
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B.pseudomallei filaments revert to normal forms when the antibiotics are removed, and daughter cells maintain cell-division capacity and viability when re-exposed to antibiotics. Thus, filamentation may be a bacterial survival strategy. In Pseudomonas aeruginosa, antibiotic-induced filamentation appears to trigger a change from normal growth phase to stationary growth phase. Filamentous bacteria also release more endotoxin (lipopolysaccharide), one of the toxins responsible for septic shock.
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A Bacillus cereus cell that has undergone filamentation following antibacterial treatment (upper electron micrograph; top right) and regularly sized cells of untreated B. cereus (lower electron micrograph) Antibiotics can induce a broad range of morphological changes in bacterial cells including spheroplast, protoplast and ovoid cell formation, filamentation (cell elongation), localized swelling, bulge formation, blebbing, branching, bending, and twisting. Some of these changes are accompanied by altered antibiotic susceptibility or altered bacterial virulence. In patients treated with β-lactam antibiotics, for example, filamentous bacteria are commonly found in their clinical specimens. Filamentation is accompanied by both a decrease in antibiotic susceptibility and an increase in bacterial virulence.
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This has implications for both disease treatment and disease progression. Antibiotics used to treat Burkholderia pseudomallei infection (mellioidosis), for example β-lactams, fluoroquinolones and thymidine synthesis inhibitors, can induce filamentation and other physiological changes. The ability of some β-lactam antibiotics to induce bacterial filamentation is attributable to their inhibition of certain penicillin-binding proteins (PBPs). PBPs are responsible for assembly of the peptidoglycan network in the bacterial cell wall.
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Nutritional stress can change bacterial morphology. A common shape alteration is filamentation which can be triggered by a limited availability of one or more substrates, nutrients or electron acceptors. Since the filament can increase a cell's uptake–surface area without significantly changing its volume appreciably. Moreover, the filamentation benefits bacterial cells attaching to a surface because it increases specific surface area in direct contact with the solid medium.
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Adv Funct Materials, 16, 885. # Gehrig, E., Hess, O., Ribbat, C., Sellin, R. L., & Bimberg, D. (2004). Dynamic filamentation and beam quality of quantum-dot lasers. Appl Phys Lett, 84, 1650.
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Inhibition of PBP-2 changes normal cells to spheroplasts, while inhibition of PBP-3 changes normal cells to filaments. PBP-3 synthesizes the septum in dividing bacteria, so inhibition of PBP-3 leads to the incomplete formation of septa in dividing bacteria, resulting in cell elongation without separation. Ceftazidime, ofloxacin, trimethoprim and chloramphenicol have all been shown to induce filamentation. Treatment at or below the minimal inhibitory concentration (MIC) induces bacterial filamentation and decreases killing within human macrophages.
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Some protein synthesis inhibitors (eg. kanamycin), RNA synthesis inhibitors (eg. bicyclomycin) and membrane disruptors (eg. daptomycin, polymyxin B) cause filamentation too, but these filaments are much shorter than the filaments induced by the above antibiotics.
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Filamentation (top right) can indicate that an antibacterial agent is targeting PBP3, FtsZ or DNA. Bioactive compounds induce phenotypic changes in target cells, changes that are observable by microscopy, and which can give insight into the mechanism of action of the compound. With antibacterial agents, the conversion of target cells to spheroplasts can be an indication that peptidoglycan synthesis is being inhibited, and filamentation of target cells can be an indication that PBP3, FtsZ or DNA synthesis is being inhibited. Other antibacterial agent-induced changes include ovoid cell formation, pseudomulticellular forms, localized swelling, bulge formation, blebbing and peptidoglycan thickening.
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The filaments, having made a plasma, turn the narrowband laser pulse into a broadband pulse having a wholly new set of applications. An interesting aspect of the filamentation induced plasma is the limited density of the electrons, a process which prevents the optical breakdown.
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The number and length of filaments within a bacterial population increases when the bacteria are treated with various chemical and physical agents (eg. DNA synthesis- inhibiting antibiotics, UV light). Some of the key genes involved in filamentation in E. coli include sulA and minCD.
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The ability to switch between yeast cells and hyphal cells is an important virulence factor. Many proteins play a role in this process. Filamentation in C. albicans is a very complex process. The formation of hyphae can for example help Candida albicans to escape from macrophages in the human body.
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This causes filamentation, and the induction of UmuDC-dependent mutagenic repair. As a result of these properties, some genes may be partially induced in response to even endogenous levels of DNA damage, while other genes appear to be induced only when high or persistent DNA damage is present in the cell.
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Overview of MAPK pathways in yeast. Non-canonical components of the five known modules (mating, filamentation, hyperosmosis, cell wall integrity, sporulation pathways) are colored in blue. MAPK pathways of fungi are also well studied. In yeast, the Fus3 MAPK is responsible for cell cycle arrest and mating in response to pheromone stimulation.
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Neural precursor cell expressed developmentally down-regulated protein 9 (NEDD-9) is a protein that in humans is encoded by the NEDD9 gene. NEDD-9 is also known as enhancer of filamentation 1 (EF1), CRK-associated substrate- related protein (CAS-L), and Cas scaffolding protein family member 2 (CASS2). An important paralog of this gene is BCAR1.
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Extreme phenomena have been observed in single-shot studies of the temporal dynamics of optical beam filamentation in air and the two-dimensional transverse profiles of beams forming multiple filaments in a nonlinear Xenon cell. In the former studies, spectral analysis of self-guided optical filaments, which were generated with pulses close to the critical power for filamentation in air, showed that the shot-to-shot statistics become heavy-tailed at the short wavelength and long wavelength edges of the spectrum. Termed optical rogue wave statistics, this behavior was studied in simulations, which supported an explanation based on pump noise transfer by self-phase modulation. In the latter experimental study, filaments of extreme intensity described as optical rogue waves were observed to emerge due to mergers between filament strings when multiple filaments are generated.
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DNA synthesis-inhibiting and DNA damaging antibiotics (eg. metronidazole, mitomycin C, the fluoroquinolones, novobiocin) induce filamentation via the SOS response. The SOS response inhibits septum formation until the DNA can be repaired, this delay stopping the transmission of damaged DNA to progeny. Bacteria inhibit septation by synthesizing protein SulA, an FtsZ inhibitor that halts Z-ring formation, thereby stopping recruitment and activation of PBP3.
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In addition, the filamentation may allows bacterial cells to access nutrients by enhancing the possibility that part of the filament will contact a nutrient-rich zone and pass compounds to the rest of the cell's biomass. For example, Actinomyces israelii grows as filamentous rods or branched in the absence of phosphate, cysteine, or glutathione. However, it returns to a regular rod-like morphology when adding back these nutrients.
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Serine-arginine family of RNA-binding protein Slr1 was found exert control on the polarized growth in Candida albicans. Slr1 mutations in mice results in decreased filamentation and reduces damage to epithelial and endothelial cells that leads to extended survival rate compared to the Slr1 wild-type strains. Therefore, this research reveals that SR-like protein Slr1 plays a role in instigating the hyphal formation and virulence in C. albicans.
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DicF RNA is a non-coding RNA that is an antisense inhibitor of cell division gene ftsZ. DicF is bound by the Hfq protein which enhances its interaction with its targets. Pathogenic E. coli strains possess multiple copies of sRNA DicF in their genomes, while non-pathogenic strains do not. DicF and Hfq are both necessary to reduce FtsZ protein levels, leading to cell filamentation under anaerobic conditions.
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At the first glance this definition may appear to be too limiting. Fortunately, due to the delicately balanced behavior of the pulses in dense media, the threshold cannot be reached easily. The phenomenon responsible for the balance is the intensity clamping through the onset of filamentation process during the propagation of strong laser pulses in dense media. A potentially important development to LIBS involves the use of a short laser pulse as a spectroscopic source.
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In addition to the mechanism described above, some antibiotics induce filamentation via the SOS response. During repair of DNA damage, the SOS response aids bacterial propagation by inhibiting cell division. DNA damage induces the SOS response in E.coli through the DpiBA two-component signal transduction system, leading to inactivation of the ftsl gene product, penicillin binding protein 3 (PBP-3). The ftsl gene is a group of filamentous temperature-sensitive genes implicated in cell division.
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First fic gene was discovered in the late 1980s in Escherichia coli. Mutation in this gene impaired cell division under stress conditions (cyclic AMP in growth medium at high temperature), which led to annotation as fic-1 for filamentation induced by cAMP. The product of fic-1 was later characterized as toxin from toxin-antitoxin system. Fic domain protein from the Vibrio parahaemolyticus VopS is a toxin secreted by type III secretion system.
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In contrast, the statistical properties were found to be approximately Gaussian for low filament numbers. It was noted that extreme spatio-temporal events are found only in certain nonlinear media even though other media have larger nonlinear responses, and the experimental findings suggested that laser-induced thermodynamic fluctuations within the nonlinear medium are the origin of the extreme events observed in multifilamention. Numerical predictions of extreme occurrences in multiple beam filamentation have also been performed, with some differences in conditions and interpretation.
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Self-focusing can also been observed in a number of soft matter systems, such as solutions of polymers and particles as well as photo- polymers. Self-focusing was observed in photo-polymer systems with microscale laser beams of either UV or visible light. The self-trapping of incoherent light was also later observed. Self-focusing can also be observed in wide-area beams, wherein the beam undergoes filamentation, or Modulation Instability, spontaneous dividing into a multitude of microscale self-focused beams, or filaments.
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The tighter focused laser has a higher peak brightness (irradiance) that forms a plasma. The plasma has an index of refraction lower than one, and causes a defocusing of the laser beam. The interplay of the focusing index of refraction, and the defocusing plasma makes the formation of a long filament of plasma that can be micrometers to kilometers in length. One interesting aspect of the filamentation generated plasma is the relatively low ion density due to defocusing effects of the ionized electrons.
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Magnetic anisotropy, for example, may occur in a plasma, so that its magnetic field is oriented in a preferred direction. Plasmas may also show "filamentation" (such as that seen in lightning or a plasma globe) that is directional. An anisotropic liquid has the fluidity of a normal liquid, but has an average structural order relative to each other along the molecular axis, unlike water or chloroform, which contain no structural ordering of the molecules. Liquid crystals are examples of anisotropic liquids.
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The Weibel instability is a plasma instability present in homogeneous or nearly homogeneous electromagnetic plasmas which possess an anisotropy in momentum (velocity) space. This anisotropy is most generally understood as two temperatures in different directions. Burton Fried showed that this instability can be understood more simply as the superposition of many counter-streaming beams. In this sense, it is like the two-stream instability except that the perturbations are electromagnetic and result in filamentation as opposed to electrostatic perturbations which would result in charge bunching.
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Adopting filamentous structures, bacteria resist these phagocytic cells and their neutralizing activity (which include antimicrobial peptides, degradative enzyme and reactive oxygen species). It is believed that filamentation is induced as a response of DNA damage (by the mechanisms previously exposed), participating SulA mechanism and additional factors. Furthermore, the length of the filamentous bacteria could have a stronger attachment to the epithelial cells, with an increased number of adhesins participating in the interaction, making even harder the work for (PMN). The interaction between phagocyte cells and adopting filamentous-shape bacteria provide an advantage to their survival.
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In order to avoid filamentation or damage to the optical elements, the entire end of the beamline is placed in a large vacuum chamber. Although Petawatt was instrumental in advancing the practical basis for the concept of fast ignition fusion, by the time it was operational as a proof-of-concept device, the decision to move ahead with NIF had already been taken. Further work on the fast ignition approach continues, and will potentially reach a level of development far in advance of NIF at HiPER, an experimental system under development in the European Union.
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A moat in a tropical cyclone is a clear ring outside the eyewall, or between concentric eyewalls, characterized by subsidence--slowly sinking air--and little or no precipitation. The air flow in the moat is dominated by the cumulative effects of stretching and shearing. The moat between eyewalls is an area in the storm where the rotational speed of the air changes greatly in proportion to the distance from the storm's center; these areas are also known as rapid filamentation zones. Such areas can potentially be found near any vortex of sufficient strength, but are most pronounced in strong tropical cyclones.
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PBPs are all involved in the final stages of the synthesis of peptidoglycan, which is the major component of bacterial cell walls. Bacterial cell wall synthesis is essential to growth, cell division (thus reproduction) and maintaining the cellular structure in bacteria. Inhibition of PBPs leads to defects in cell wall structure and irregularities in cell shape, for example filamentation, pseudomulticellular forms, lesions leading to spheroplast formation, and eventual cell death and lysis. PBPs have been shown to catalyze a number of reactions involved in the process of synthesizing cross-linked peptidoglycan from lipid intermediates and mediating the removal of D-alanine from the precursor of peptidoglycan.
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For silica, n0 ≈ 1.453, n2 ≈ 2.4×10−20 m2/W, and the critical power is Pcr ≈ 2.8 MW. Kerr-induced self-focusing is crucial for many applications in laser physics, both as a key ingredient and as a limiting factor. For example, the technique of chirped pulse amplification was developed to overcome the nonlinearities and damage of optical components that self-focusing would produce in the amplification of femtosecond laser pulses. On the other hand, self-focusing is a major mechanism behind Kerr-lens modelocking, laser filamentation in transparent media, self-compression of ultrashort laser pulses, parametric generation, and many areas of laser-matter interaction in general.
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Inhibition of FtsZ disrupts septum formation, resulting in filamentation of bacterial cells (top right of electron micrograph). During cell division, FtsZ is the first protein to move to the division site, and is essential for recruiting other proteins that produce a new cell wall (septum) between the dividing cells. FtsZ's role in cell division is analogous to that of tubulin in eukaryotic cell division, but, unlike the actin-myosin ring in eukaryotes, FtsZ has no known motor protein associated with it. The origin of the cytokinetic force, thus, remains unclear, but it is believed that the localized synthesis of new cell wall produces at least part of this force.
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The biochemicals trigger the fungal organism to react in a specific manner, while if the same chemical molecules are not part of biotic messages, they do not trigger the fungal organism to react. This implies that fungal organisms can differentiate between molecules taking part in biotic messages and similar molecules being irrelevant in the situation. So far five different primary signalling molecules are known to coordinate different behavioral patterns such as filamentation, mating, growth, and pathogenicity. Behavioral coordination and production of signaling substances is achieved through interpretation processes that enables the organism to differ between self or non-self, a biotic indicator, biotic message from similar, related, or non-related species, and even filter out "noise", i.e.
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The balance between the self-focusing refraction and self-attenuating diffraction by ionization and rarefaction of a laser beam of terawatt intensities, created by chirped pulse amplification, in the atmosphere creates "filaments" which act as waveguides for the beam thus preventing divergence. Competing theories, that the observed filament was actually an illusion created by an axiconic (bessel) or moving focus instead of a "waveguided" concentration of the optical energy, were put to rest by workers at Los Alamos National Laboratory in 1997. Though sophisticated models have been developed to describe the filamentation process, a model proposed by Akozbek et al.N Aközbek, CM Bowden, A Talebpour, SL Chin, Femtosecond pulse propagation in air: Variational analysis, Phys. Rev.
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She showed that the CZF1 gene is a regulator of the filamentation response, and that Mkc1 and Cek1 (MAP kinases) are activated when cells are grown in contact with the agar. She has demonstrated that certain dietary fats, including coconut oil, can suppress the growth of C. albicans in the gut, decreasing the risk of fungal infections. It has been proposed that this finding will decrease the need for antifungal drugs and could be used to decrease the amount of C. albicans in the guts of premature infants. In 2019, Kumamoto reported the first results of a clinical trial that involved supplementing the diets of preterm infants with medium-chain triglycerides to reduce the amount of C. albicans in the gastrointestinal tract.
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Striations or string-like structures, also known as Birkeland currents, are seen in many plasmas, like the plasma ball, the aurora, lightning, electric arcs, solar flares, and supernova remnants.. The University of Arizona They are sometimes associated with larger current densities, and the interaction with the magnetic field can form a magnetic rope structure. High power microwave breakdown at atmospheric pressure also leads to the formation of filamentary structures. (See also Plasma pinch) Filamentation also refers to the self-focusing of a high power laser pulse. At high powers, the nonlinear part of the index of refraction becomes important and causes a higher index of refraction in the center of the laser beam, where the laser is brighter than at the edges, causing a feedback that focuses the laser even more.
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Observation of NGC 6810 with XMM-Newton reveals the presence of extended soft X-ray emission within the optical disc of the galaxy (which is closely associated with star-forming regions) and also beyond the optical disc. This, along with Hα filamentation and peculiar minor axis ionized gas kinematics, strongly suggest that NGC 6810 is host to a galactic- scale superwind which is streaming from the starburst region. The actively star-forming regions and the base radius of the outflow are unusually spread out, and extend out to a radius of ∼6.5 kpc from the nucleus. Most superwinds in other galaxies appear to arise in ≲ 1 kpc-scale nuclear starburst regions. That makes NGC 6810 one of the few ‘disc-wide’ superwinds currently known, because NGC 6810's superwind base extends across nearly 70 percent of the entire galaxy's diameter.
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This failure by Shiva to efficiently heat the compressed plasma pointed to the use of optical frequency multipliers as a solution which would frequency triple the infrared light from the laser into the ultraviolet at 351 nm. Newly discovered schemes to efficiently frequency triple high intensity laser light discovered at the Laboratory for Laser Energetics in 1980 enabled this method of target irradiation to be experimented with in the 24 beam OMEGA laser and the NOVETTE laser, which was followed by the Nova laser design with 10 times the energy of Shiva, the first design with the specific goal of reaching ignition conditions. Nova also failed in its goal of achieving ignition, this time due to severe variation in laser intensity in its beams (and differences in intensity between beams) caused by filamentation which resulted in large non- uniformity in irradiation smoothness at the target and asymmetric implosion. The techniques pioneered earlier could not address these new issues.
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