DegU-P represses expression of the motility fla-che operon in Bacillus subtilis.
J Bacteriol
; 186(18): 6003-14, 2004 Sep.
Article
em En
| MEDLINE
| ID: mdl-15342569
ABSTRACT
Bacillus subtilis implements several adaptive strategies to cope with nutrient limitation experienced at the end of exponential growth. The DegS-DegU two-component system is part of the network involved in the regulation of postexponential responses, such as competence development, the production of exoenzymes, and motility. The degU32(Hy) mutation extends the half-life of the phosphorylated form of DegU (DegU-P); this in turn increases the production of alkaline protease, levan-sucrase, and other exoenzymes and inhibits motility and the production of flagella. The expression of the flagellum-specific sigma factor SigD, of the flagellin gene hag, and of the fla-che operon is strongly reduced in a degU32(Hy) genetic background. To investigate the mechanism of action of DegU-P on motility, we isolated mutants of degU32(Hy) that completely suppressed the motility deficiency. The mutations were genetically mapped and characterized by PCR and sequencing. Most of the mutations were found to delete a transcriptional termination signal upstream of the main flagellar operon, fla-che, thus allowing transcriptional readthrough from the cod operon. Two additional mutations improved the sigmaA-dependent promoter sequence of the fla-che operon. Using an electrophoretic mobility shift assay, we have demonstrated that purified DegU binds specifically to the PA promoter region of the fla-che operon. The data suggest that DegU represses transcription of the fla-che operon, and they indicate a central role of the operon in regulating the synthesis and assembly of flagella.
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Bases de dados:
MEDLINE
Assunto principal:
Óperon
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Bacillus subtilis
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Proteínas de Bactérias
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Adaptação Fisiológica
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Regulação Bacteriana da Expressão Gênica
Idioma:
En
Revista:
J Bacteriol
Ano de publicação:
2004
Tipo de documento:
Article
País de afiliação:
Itália