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Статті в журналах з теми "Bactéries flagellées"
Szelag-Wasielewska, E. "Biocénose pélagique du lac oligomésotrophe de Poméranie (Pologne) : étude des communautés de la boucle mocrobienne et du pytoplancton." Revue des sciences de l'eau 15, no. 1 (April 12, 2005): 27–35. http://dx.doi.org/10.7202/705433ar.
Повний текст джерелаKaur, Bhavleen, and Henrietta Mann. "ULTRASTRUCTURE AND CHARACTERISTICS OF A DEEP-SEA BACTERIUM." Proceedings of the Nova Scotian Institute of Science (NSIS) 42, no. 2 (November 1, 2004). http://dx.doi.org/10.15273/pnsis.v42i2.3616.
Повний текст джерелаДисертації з теми "Bactéries flagellées"
Duchesne, Ismael. "La motilité des bactéries flagellées en milieu anisotrope." Doctoral thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/34999.
Повний текст джерелаBacteria play an essential role in nature. We can simply think of their impact on human health to convince ourselves. To be able to play their role in the environment, bacteria often need to reach specific locations. The most common bacterial locomotion system is the flagellar motor. To propel themselves, the flagellated bacteria possess one (or few) rotary motor anchored in their membrane. This motor transfers its rotation to a long helical filament located outside the bacterium thanks to a universal joint called the hook. This motor was the first biological rotary motor discovered. Furthermore, several studies have shown the importance of the flagellar motor during bacterial infections. Thus, it has been the subject of intensive studies for several decades. Most of these studies, however, have been conducted in simple media that represent only a small fraction of natural biological environment. Indeed, bacteria often move in anisotropic media, where the physical properties depend on the direction. For example, mucus found throughout the human body, synovial fluid that lubricates our joints, skin and biofilms are all media that can be anisotropic and where bacteria proliferate. This thesis by article presents our study of the motility of flagellar bacteria in anisotropic media. Since natural biological media are difficult to manipulate in the laboratory, a synthetic medium was first chosen to mimic the properties of natural anisotropic media. Two types of anisotropic media were tested, the liquid crystals (LCs) 5CB and DSCG. Only the LC DSCG has been used since bacteria cannot penetrate the LC 5CB. To create the DSCG LC, molecules of disodium cromoglycate (DSCG) are dissolved in a water-based solvent. At low concentration, the medium is isotropic, and at high concentration the medium becomes anisotropic (a LC). First, the speed and the orientation of the body of the bacteria were recorded while changing the concentration of the DSCG LC to bring the solution from the isotropic phase to the anisotropic phase. These measurements first confirmed that, in an anisotropic environment, the bacteria move in a straight line and reverse their movement rather than performing a random walk as in isotropic media. Observation of bacterial behavior also demonstrated the presence of a pretransition zone in isotropic solutions of DSCG. At these concentrations of DSCG, the molecules begin to organize into rods. This organization explains why bacteria become sticky (via the depletion force), and why the viscosity increases in the pretransition zone. To understand how bacteria can reverse their motion in anisotropic media, the filaments have also been studied. These observations have shown that during the change of direction of the bacteria, the hook is no longer a universal joint and momentarily locks, thus changing the orientation of the filament. This reorientation of the filament does not only reverse the movement of the bacteria in the LC, but it also triggers the reorientation of the filament in other media as in porous media. This observation, supplemented by results from literature, suggests that the blocked hook is a universal phenomenon occurring in all environments. Finally, light-guided dark field microscopy and a microrheological technique will be exposed. These techniques were used during the characterization of the pretransition zone. Throughout this work, it will also be highlighted how our multidisciplinary approach has been beneficial.
Chalmeau, Jérôme. "Contribution from nanotechnologies to the study and assembly of the flagellar nano-motor of bacteria." Toulouse, INSA, 2009. http://eprint.insa-toulouse.fr/archive/00000343/.
Повний текст джерелаThe bacteria flagellar nanomotor is a nature marvel due to its structure and importance for bacteria. It allows the rotation at high frequency ( 300 Hz) of a long external filament. This filament plays a role comparable to a submarine helix and propels its host in the liquid environment. Despite its size, 45 nm at the largest diameter, this nano-bio-machine is composed of thousands of proteins. These proteins work together in order to generate the flagellar rotation and allow bacteria to swim freely in a liquid environment. Despite its importance for bacteria’s life, its precise mechanism remains unclear today. This motor was discovered more than 3o years ago and a large number of experimental data and hypotheses about its structure and mechanism have been accumulated. The overall assembly, the crystal structure of some constitutive proteins, and the role played by each component permit to draw a possible architecture of the motor. Others experiments has also highlighted some crucial aspects of this machine, through mechanical measurement of the torque developed by the motor, in order to define the torque/speed relationship. However, the nanoscale description of the motor remains limited and many interpretations are still questionable. In this work, I have developed two ambitious parallel and complementary ways to elucidate some open questions: the in vitro re-assembly in a control maner of an essential part of the motor, and a large scale study of the interactions between identified motor’s proteins crucial for the motor rotation. These approaches have been supported by the use of new tools, which had never been used before for studying this nano-motor: the Atomic Force Microscope (AFM), for visualizing in a close native environment part of the motor reassembled, and the Quartz Micro Balance for the interactions study. New experimental datas have been obtained and permitted to propose a new hypothesis of the mechanism of the Bacteria Flagellar Nano-Motor
Lemaire, Laurine. "Étude des propriétés physico-chimiques de la membrane plasmique comme facteurs modulant l'interaction de molécules et des structures protéiques exogènes." Electronic Thesis or Diss., Compiègne, 2022. http://www.theses.fr/2022COMP2713.
Повний текст джерелаThe plasma membrane was often described as a structure delimiting and protecting the cell from its external environment. However, his role is much more complex and multifunctional. The membrane is an exchange platform at the cellular external and internal environments. Many cellular functions are closely related to it, such as migration, transport of molecules, some pathways of metabolic signaling, or the contact with micro-organisms. This thesis focuses on the study of some cellular processes occurring at the membrane interface using a system that can mimic the lipid bilayer properties. This membrane models that allow a precise control of the in vitro conditions, represent a good alternative to the often inconclusive studies on whole cells. Liposomes allow focusing on a particular function or constituent. In this thesis, the use of the biomimetic model was declined for the study of several processes. The mechanisms of adhesion of flagellated bacteria to lipid bilayers were studied as a function of the physical properties of the lipid bilayers. This information is of paramount importance in the context of antibiotic resistance, giving more information for the potential development of alternative therapies. The liposome model was also used for forming proteoliposomes to study of a transmembrane protein, MRP4 (multidrug resistance associated protein). The study of this protein is an issue in multi-drug treatments. Indeed, this protein is widely involved in drug interactions. Finally, the liposome model was used to characterize the interaction with lipid bilayers of molecules with high therapeutic potential: polyphenols. All of this work was done in collaboration with the team of the Prof Patrick Trouillas (INSERM U1248 team, Limoges University Hospital) working on the development of biomimetic cell models in silico
Arnold, Françoise. "Étude de la flagelline de Clostridium tyrobutyricum ATCC 25755 : analyse biochimique et séquencage de la partie codante du gène." Brest, 1997. http://www.theses.fr/1997BRES2042.
Повний текст джерелаHoury, Ali. "Rôle des flagelles et de la mobilité dans la formation de biofilms par Bacillus cereus." Paris 11, 2009. http://www.theses.fr/2009PA112369.
Повний текст джерелаBacillus cereus is an opportunistic pathogen frequently associated with food poisoning and involved in rare but severe local or systemic infections. Contamination of food industry products by B. Cereus can result in economical injuries and might raise safety concerns. The capacity of B. Cereus to form biofilm on different surfaces increases its persistence in the food industry equipments. Here, we have determined the dynamics of biofilm formation by B. Cereus and the roles played by flagella and flagellar motility in B. Ce reus biofilm formation in different growth conditions. We have shown that, in static cultures runned in glass tubes or in microtiter plates, flagellar motility is required for biofilm formation. Motility was necessary for the bacteria to have access to the air-liquid interface where the biofilm develops. Flagellar motility was also involved in the recruitment of planktonic bacteria by the biofilm and promoted biofilm expansion on the colonized surface. We found that B. Cereus is able to form immersed biofilms in continuous flow conditions in flowcells. However, in these growth conditions, flagellar motility was not required for biofilm formation. Observation of biofilms by confocal microscopy have shown the presence of a subpopulation of bacteria able to move through the different biofilm. The speed of these mobile bacteria could reach values up to approximately 16 μm/s. This speed decreased when the biofilm became older and mature, probably as a consequence of an increase in the exopolysaccharide matrix density. Finally, we demonstrated that flagellar mobility was involved in the bacterium pathogenicity in an isect model. In this model, larvae of the wax moth Galleria mellonela was infected by the oral route. Motility, but not the simple presence of flagella, promoted adhesion of bacteria on epithelial HeLa cells
Karayanni, Héra. "Rôle des nanoflagellés hétérotrophes et des ciliés dans la régulation du pico- et nanoplancton photosynthétique et des bactéries en Atlantique NE et le recyclage de la matière organique." Aix-Marseille 2, 2004. http://www.theses.fr/2004AIX22063.
Повний текст джерелаTruchon, Dany. "Nouveaux marqueurs pour l'observation du moteur flagellaire bactérien." Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/28827/28827.pdf.
Повний текст джерелаOry, Pascaline. "Interactions entre les virus, les flagellés et les bactéries au sein du réseau microbien planctonique du bassin de Marennes-Oléron." Thesis, La Rochelle, 2010. http://www.theses.fr/2010LAROS294.
Повний текст джерелаPlanktonic microbial compartments are important in the trophic and biogeochemical functioning of marine ecosystems. This assessment brought us to place these objectives: characterization of virus, bacteria and flagellate compartments and their interactions in Marennes-Oléron Bay (France). Two different approaches have been followed: 1) In situ annual surveys were performed in 2006 and 2007 in order to characterize microbial compartments dynamics and to place them within the bay functioning, compared to Arcachon Bay. The succession of trophic models implied the importance of the microbial food web in both bays. In Marennes Oléron Bay, spatially homogeneous, large inter annual and inter seasonal variations are observed considering the strength of the common link between virioplankton and bacterioplankton. These variations are related to the occurrence of an occasional interaction of phytoplankton. 2) In vitro experiments allow to focus on the processes controlling the dynamics of viruses, flagellates and bacteria and their interactions. The impacts of viral bacteriolysis and flagellate bacterivory are assessed considering environmental variability factors: trophic models, predation pressure and influence of benthic contribution. The bacterial community composition is always influenced by viral lysis and bacterivory due to the sensitivity of bacterial groups. However, bacterial cellular production evolves differently with a stimulation by flagellates during herbivorous food web while bacterivory induces daily production loss of 16% during multivorous food web. Finally, the resuspension of benthic organic components during tide phase tends to increase the microbial loop activity
Soutourina, Olga. "Contrôle de l'expression des gènes dans le processus de motilité chez les bactéries à Gram-négatif." Versailles-St Quentin en Yvelines, 2001. http://www.theses.fr/2001VERS011V.
Повний текст джерелаGauthier, Mathieu. "Développement d'un système in vitro pour l'étude du moteur flagellaire bactérien d'Escherichia coli." Doctoral thesis, Université Laval, 2011. http://hdl.handle.net/20.500.11794/23107.
Повний текст джерелаЧастини книг з теми "Bactéries flagellées"
PENG, Chenhui, and Oleg D. LAVRENTOVICH. "Contrôle des microparticules avec des cristaux liquides." In Cristaux liquides, 103–40. ISTE Group, 2022. http://dx.doi.org/10.51926/iste.9040.ch2.
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