Bahlawane discussion Essay

Conclusion victorious in account the scheme of galactoglucan deductive reasoning code (Fig. 4. 1) and the scheme of campaign regulation (Fig. 4. 2) proposed in this study, we may try to meet the personnel of such regulation paths in the spiritedness styles of the bacterium. The suffer one is named as free living microorganism or as symbiont in the plant root. In the start case, the bacteria argon clear to dryness and nutrients starvation. At this stage, the biofilm production is a pre-requisite for survival. Therefore, the EPSs biosynthesis has to be switched ON.As it is quite improbable that the prison cellular telephone parsimony is high enough to activate the quorum perceptual experience system, we can speculate that MucR plays a get a line role in activating the succinoglycan biosynthesis. Since the speck exhibits real low level of Pi, galactoglucan is, at this point produced through the activation via phoB and WggR. Upon biofilm formation, the cell density probably increases and could activate the quorum signal detection system, allowing the bacteria to produce more than galactoglucan and bevy towards better conditions.In such conformation, the cells bring in within the centre of the swarming population are non motile and synthesized EPS thus the cells present at the migration front are highly motile only when do non synthesized EPS. It would be interesting to clarify whether a cell diametricaliation, as proposed by Soto (Soto et al. , 2002), takes place at this stage. Finally, if the host is present in the beside neighbourhood the chemotactic compounds, as well as the nutrients found in the rood exudates, provide attract the bacteria.When approaching the root, the moisture increases, along with the nutrients availability so that swarming motility bequeath be replaced by fluid motility that decline progressively. Indeed, the bacteria attached to the root, increase the cell density that may stretch forth to the inhibition o f flagella production via ExpR / QS. Instead, EPS are produced, allowing identification between the plant and the microbe as well as the invasion of the new(a) synthesized contagion thread. Once within the root, the bacteria will differentiate to bacteroid and starting line fixing nitrogen.We tried to highlight in this thesis the relevance of exopolysaccharides and motility for an economic mutualism. Great advances give up been made the last years, leadership to the identification of the quorum sensing fundamental interaction with motility. We participate in inclusion of MucR, as new regulator of motility and ExpR as requisite for swarming. However, the full understanding of the beguile of motility in symbiosis mental home will require finding push through which signals are inducing mucR and exoR/ exoS.Moreover, some tests have to be implemented to investigate the symbiosis establishment in more living conditions. Indeed, the bacteria are usually right off inoculated to the root, so that motility, via swarming or swimming is not necessitate. Acknowledgments First and foremost, I would wish well to convey Prof. Dr. Alfred Puhler, Chair of the Genetics department, for allowing me use the genuinely good infrastructure that promotes a very pleasant and conducive atmosphere during my investigate using performant techniques. I am in particular grateful to Prof.Dr. Anke Becker, my supervisor, for giving me the chance to act back to research. Without her advices, ideas and resources, this convey would not be possible and achieved. Thus, I convey her as well for the freedom she gave me, as well as her remain firm to test new ideas and her with child(p) help by conceiving and writing the manuscripts that operate the pillars of this manuscript. Within the laboratory members, I would care to thank first Dr. Birgit Baumgarth who introduced me to the lab and to the investigated organism.Then, particular(prenominal) thanks to Dr.Matthew McIntosh for the quorum sensing related work and his help for preparing the derived publication. Furthermore, I would like to late thank Dr. Natasha Pobigaylo for her friendship, her helpful discussions and for giving me bravery when I am about to digest it. I thank Manuela Mayer, too, for the assistance in microarray hybridizations as well as Dr. Lisa Krol, Javier Serrania and doubting Thomas Montfort for the everyday help in the lab. Finally, I would like to thank all Exopol convention members for the support and advices.Least, I would like to thank my family for their unending and heartwarming support in many ways. Special thanks to Rachida Bendaou, my mother-in-law, for her support in caring my children during my research. I would like to thank my children, Ines, Soraya and Jasmine, for filling up my life with love and happiness. I would like to apologize for the bad mood and stress steads that are unfortunately connected with such a thesis. My heartfelt gratitude to my understanding and loving husband, Naoufal, for his clean-living and financial support, for believing in me and for sharing the passion for science with me.Resume In order to enter symbiosis with its legume partner, Sinorhizobium meliloti has to face continual changing conditions. It has more ability to adapt quickly to the situation than the ability to face it efficiently that makes the end in term of symbiosis efficiency. For the first interactions with its host, motility is required by S. meliloti to hunt towards the chemotactic compounds released by its host when exopolysaccharides (EPSs) are required later on, for the attachment to the root as well as for the invasion of the infection thread, leading to the formation of the root nodule.We focussed in this study the regulatory networks leading to the coordination of motility and EPSs production in the strain Rm2011. Depending on the phosphate concentration encountered in the environment Rm2011 synthesizes two different exopolysaccharides (EPS). Galactoglucan (EPS II) is produced under phosphate starvation but also in the presence of particular(a) copies of the arrangingal regulator WggR (ExpG) or as a consequence of a mutation in mucR. The galactoglucan biosynthesis gene cluster contains the operons wga (expA), wge (expE), wgd (expD), and wggR (expG). both promoters, differentially controlled by WggR, PhoB, and MucR, were identified upstream of each of these operons. The proximal promoters of the wga, wge, and wgd transcription units were constitutively participating when separated from the upstream regulatory sequences. proveman activity studies and the positions of predicted PhoB and WggR salad dressing sites suggested that the proximal promoters are cooperatively induced by PhoB and WggR. MucR was shown to powerfully inhibit the distal promoters and bound to the desoxyribonucleic acid in the vicinity of the distal transcription start sites.An additional inhibitory effect on the distal promoter of the geomo rphological galactoglucan biosynthesis genes was identified as a new feature of WggR in a mucR mutant. Motility is organized in S. meliloti in a hierarchical cascade, with break Ia genes, encryption the major regulator of motility VisNR despotic the musing of the class Ib gene, rem, which encodes a cardinal regulator, activating the building of the downstream Class II and class III genes. We could wrangle that MucR binds a DNA sequence upstream of rem, following a different machine as previously observed upon binding upstream of the wg genes.By this way, MucR inhibits rem expression as well as the expression of the Rem-regulated genes such as flaF and flgG. Furthermore, we addressed a balance of the swimming and swarming abilities of several S. meliloti strains derivatives of Rm2011.We could show that all strains, able to build flagella, were swimming on low viscosity nutrient agar-agar plates. However, swarming over high viscosity agar plates required all a functional expR / sin locus, the ability to build flagellum and the production of exopolysaccharides. Finally, we propose a archetype for the coordination of motility and EPSs synthesis in S. meliloti.