Plasmid-amplified comS enhances genetic competence and suppresses sinR in Bacillus subtilis.
The establishment of genetic competence in Bacillus subtilis is controlled by a vast signal transduction network involving the products of genes that function in several postexponential-phase processes. Two of these proteins, SinR and DegU, serve as molecular switches that influence a cell's decision to undergo either sporulation or genetic competence development. In order to determine the roles of SinR and DegU in competence control, multicopy suppression experiments with plasmid-amplified comS, SinR, and degU genes were undertaken. Multicopy comS was found to elevate competence gene transcription and transformation efficiency in both wild-type and sinR mutant cells but not in degU mutant cells. Multicopy degU failed to suppress comS or sinR mutations. No suppression of comS or degU by multicopy sinR was observed. The expression of a comS'::'lacZ translational fusion and srf-lacZ operon fusion was examined in sinR cells and cells bearing plasmid-amplified sinR. The expression of comS'::'lacZ gene fusion was reduced by the sinR mutation, but both comS'::'lacZ and srf-lacZ were repressed by multicopy sinR. Cells bearing plasmid-amplified sinR were poorly competent. These results suggest that sinR is required for optimal comS expression but not transcription from the srf promoter and that SinR at high concentrations represses srf transcription initiation.
Liu
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Department of Biochemistry and Molecular Biology, Louisiana State University Medical Center, Shreveport, USA.
Nakano
M M
MM
Lee
O H
OH
Zuber
P
P
D001412:Bacillus subtilis / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D007763:Lac Operon; D009154:Mutation; D009876:Operon; D010453:Peptide Synthases / Q000235:genetics; D010957:Plasmids; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics* / Q000502:physiology; D013489:Suppression, Genetic; D014158:Transcription, Genetic
D001426:Bacterial Proteins; C093539:ComS protein, Bacillus subtilis; D004268:DNA-Binding Proteins; C066497:DegU protein, Bacteria; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; C083616:mecA protein, Bacillus subtilis; C076733:FlaD protein, Bacteria; D010453:Peptide Synthases; C069542:surfactin synthetase