Functional Differences of Two Distinct Catalases in Mesorhizobium loti MAFF303099 under Free-Living and Symbiotic Conditions▿

Protection against reactive oxygen species (ROS) is important for legume-nodulating rhizobia during the establishment and maintenance of symbiosis, as well as under free-living conditions, because legume hosts might assail incoming microbes with ROS and because nitrogenase is extremely sensitive to ROS. We generated mutants of two potential catalase genes in Mesorhizobium loti MAFF303099 to investigate their physiological significance. Biochemical results indicated that genes with the locus tags mlr2101 and mlr6940 encoded a monofunctional catalase and a bifunctional catalase-peroxidase, respectively, that were named katE and katG. Under free-living conditions, the katG mutant demonstrated an extended generation time and elevated sensitivity to exogenous H2O2, whereas the katE mutant exhibited no generation time extension and only a slight increase in sensitivity to exogenous H2O2. However, the katE mutant showed a marked decrease in its survival rate during the stationary phase. With regard to symbiotic capacities with Lotus japonicus, the katG mutant was indistinguishable from the wild type; nevertheless, the mutants with disrupted katE formed nodules with decreased nitrogen fixation capacities (about 50 to 60%) compared to those formed by the wild type. These mutant phenotypes agreed with the expression profiles showing that transcription of katG, but not katE, was high during the exponential growth phase and that transcription levels of katE versus sigA were elevated during stationary phase and were approximately fourfold higher in bacteroids than mid-exponential-phase cells. Our results revealed functional separation of the two catalases, as well as the importance of KatE under conditions of strong growth limitation

Special Beam Position Monitor With 8-Button Electrodes

To maintain the optimum collision condition of the two beams, two special BPMs with 8-button electrodes, called OCTOPOS, were installed inside the super-conducting quadrupole magnets (QCSs) at the interaction region (IR) of KEKB. We have commissioned the OCTOPOS BPMs for simultaneous measurements of both the electron and positron beam positions from their composite signal. A collision orbital feedback using OCTOPOS has been put into practical application since last November. The position of each beam is separable by analyzing the nonlinearity of the pickup sensitivity from the signal amplitudes of the eight button electrodes. This report describes the characterization of the OCTOPOS and its performance

Total synthesis and absolute stereochemistry of (+)-batzellaside B and its C8-epimer, a new class of piperidine alkaloids from the sponge Batzella sp

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