Role of regulatory features of the trp operon of Escherichia coli in mediating a response to a nutritional shift.

摘要: Physiological studies were performed under nutritional stress and nonstress conditions to assess the relative importance of various regulatory mechanisms that Escherichia coli can use alter its rate tryptophan synthesis. Mutants examined in which trp repressor was inactive, transcription termination at attenuator altered, initiation promoter reduced, or feedback inhibition anthranilate synthase abolished. Strains media with without tryptophan, phenylalanine tyrosine, acid-hydrolyzed casein following shifts from one medium another. Growth rates levels measured. In lacking each mutants showed relief repression and/or attenuation maintained a near-normal growth rate. Following shift containing tryptophan-free tyrosine casein, abnormally low enzyme exhibited an appreciable lag before resuming growth. The wild-type strain displayed only extreme condition, upon transfer minimal tyrosine. A down-mutant had difficulty adjusting high casein. all tested, lower feedback-resistant mutant than wild type. These demonstrate capacity E. adjust synthesis maintain rapid stressful conditions.