Untersuchungen zur generellen Stressantwort von Bacillus subtilis nach Einwirkung von Umweltstress und bei niedriger Temperatur

Abstract The alternative sigma factor SigB controls the expression of the general stress regulon in Bacillus subtilis. The synthesis of general stress proteins supplies non-growing cells of Bacillus subtilis with an unspecific, multiple and precautionary resistance to future stress. To understand the function and interconnection of the general stress response in the adaptation network of Bacillus subtilis, DNA-macroarrays were used to monitor the changes in the transcriptome of cells exposed to heat, salt or ethanol. This macroarray contains PCR-products of all 4107 annotated genes of this Gram-positive model organism. In total 124 SigB-dependent genes were identified containing 62 previously known SigB-depending genes and 62 genes newly assigned to the SigB-regulon. As another result the induction of the ECF-sigma factor SigW after 4% salt stress was shown. In dot blot experiments the induction of the SigW-regulon after salt stress was osmotically controlled. Additionally, the induction of the general stress response was monitored with lacZ- and gfp-reporter fusions during the growth at low temperature. In contrast to the transient induction pattern after environmental stress the induction during the continuous growth at low temperature was continuous in exponential growing cells. The analysis of different regulator mutants of the SigB-activity confirmed the temperature sensitive phenotype of the sigB-mutant and revealed the growth defect of the rsbP- and rsbUP-mutants due to the weak induction of general stress proteins in these cells. A deletion of the rsbV-gene in the rsbUP-mutant recovered the full induction of the used gfp-reporter fusion. This rsbUPV-triple mutant also had no growth sensitive phenotype. The high and continuous induction of the general stress response supports the hypothesis of a new signal transduction pathway to activate SigB in the cold.Abstract The alternative sigma factor SigB controls the expression of the general stress regulon in Bacillus subtilis. The synthesis of general stress proteins supplies non-growing cells of Bacillus subtilis with an unspecific, multiple and precautionary resistance to future stress. To understand the function and interconnection of the general stress response in the adaptation network of Bacillus subtilis, DNA-macroarrays were used to monitor the changes in the transcriptome of cells exposed to heat, salt or ethanol. This macroarray contains PCR-products of all 4107 annotated genes of this Gram-positive model organism. In total 124 SigB-dependent genes were identified containing 62 previously known SigB-depending genes and 62 genes newly assigned to the SigB-regulon. As another result the induction of the ECF-sigma factor SigW after 4% salt stress was shown. In dot blot experiments the induction of the SigW-regulon after salt stress was osmotically controlled. Additionally, the induction of the general stress response was monitored with lacZ- and gfp-reporter fusions during the growth at low temperature. In contrast to the transient induction pattern after environmental stress the induction during the continuous growth at low temperature was continuous in exponential growing cells. The analysis of different regulator mutants of the SigB-activity confirmed the temperature sensitive phenotype of the sigB-mutant and revealed the growth defect of the rsbP- and rsbUP-mutants due to the weak induction of general stress proteins in these cells. A deletion of the rsbV-gene in the rsbUP-mutant recovered the full induction of the used gfp-reporter fusion. This rsbUPV-triple mutant also had no growth sensitive phenotype. The high and continuous induction of the general stress response supports the hypothesis of a new signal transduction pathway to activate SigB in the cold.