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Benzoate Decreases the Binding of cis,cis-Muconate to the BenM Regulator despite the Synergistic Effect of Both Compounds on Transcriptional Activation. Todd J. Clark, 2004.Fluorescence emission spectroscopy was used to investigate interactions between two effectors and BenM, a transcriptional regulator of benzoate catabolism . BenM had a higher affinity for cis,cis-muconate than for benzoate as the sole effector . However, the presence of benzoate increased the apparent dissociation constant [reduced the affinity] of the protein for cis,cis-muconate . Similar results were obtained with truncated BenM lacking the DNA-binding domain . High-level transcriptional activation may require that some monomers within a BenM tetramer bind benzoate and others bind cis,cis-muconate . Control of Pseudomonas aeruginosa algZ Expression by the Alternative Sigma Factor AlgT. Daniel J. Wozniak, 2003.AlgZ controls Pseudomonas aeruginosa alginate synthesis by activating algD, yet algZ expression is not detectable in nonmucoid strains . Mobility shift and Western blot assays revealed that algZ expression requires the sigma factor AlgT. The mapped algZ transcription start site revealed a consensus AlgT-dependent promoter that, when mutated, substantially reduced algZ transcription . Involvement of the Reserve Material Poly-ß-Hydroxybutyrate in Azospirillum brasilense Stress Endurance and Root Colonization. Daniel Kadouri, 2003.When grown under suboptimal conditions, rhizobacteria of the genus Azospirillum produce high levels of poly-ß-hydroxybutyrate (PHB) . Azospirillum brasilense strain Sp7 and a phbC (PHB synthase) mutant strain in which PHB production is impaired were evaluated for metabolic versatility, for the ability to endure various stress conditions, for survival in soil inoculants, and for the potential to promote plant growth . The carbon source utilization data were similar for the wild-type and mutant strains, but the generation time of the wild-type strain was shorter than that of the mutant strain with all carbon sources tested . The ability of the wild type to endure UV irradiation, heat, osmotic pressure, osmotic shock, and desiccation and to grow in the presence of hydrogen peroxide was greater than that of the mutant strain . The motility and cell aggregation of the mutant strain were greater than the motility and cell aggregation of the wild type . However, the wild type exhibited greater chemotactic responses towards attractants than the mutant strain exhibited . The wild-type strain exhibited better survival than the mutant strain in carrier materials used for soil inoculants, but no difference in the ability to promote plant growth was detected between the strains . In soil, the two strains colonized roots to the same extent . It appears that synthesis and utilization of PHB as a carbon and energy source by A . brasilense under stress conditions favor establishment of this bacterium and its survival in competitive environments . However, in A . brasilense, PHB production does not seem to provide an advantage in root colonization under the conditions tested .
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