Gradual activation of the response regulator DegU controls serial expression of genes for flagellum formation and biofilm formation in Bacillus subtilis
Gradual activation of the response regulator DegU controls serial expression of genes for flagellum formation and biofilm formation in Bacillus subtilis
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DOI：
10.1111/j.1365-2958.2007.05923.x
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发表时间：
2007-10-01
影响因子：
3.6
通讯作者：
Kobayashi, Kazuo
中科院分区：
文献类型：
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作者：
Kobayashi, Kazuo
在自然环境中，细菌在作为能动细胞生长和作为固着的生物膜形成细胞生长之间波动。然而，是什么控制了枯草芽孢杆菌中这两种生长模式之间的转换还没有很好地理解。degU突变阻止鞭毛形成和生物膜形成，这表明其中一种过渡机制可能是DegU活性调节的基础。DegU调节基因的表达谱不同;鞭毛基因和几个未知基因在指数期表达，而其他基因在稳定期诱导。degS突变不影响flgB-sigD操纵子的转录，但降低sigma（D）依赖性鞭毛基因、degU和其他DegU调节基因的转录。此外，degQ突变不影响鞭毛基因的转录，但减少其他DegU调节基因的转录。纯化的DegQ蛋白在体外刺激从磷酸化DegS到DegU的磷酸转移。此外，DegU以高亲和力结合flgB的启动子区，而DegU以低亲和力和DegS依赖性方式结合其它DegU调节的基因的启动子区。综上所述，我们提出DegU和磷酸化DegU水平的逐渐增加诱导从作为运动细胞生长到作为固着生物膜形成细胞生长的过渡。
In natural environments, bacteria fluctuate between growth as motile cells and growth as sessile, biofilm-forming cells. However, what controls the transition between these two-growth modes in Bacillus subtilis is not well understood yet. The degU mutation prevents both flagellum formation and biofilm formation, suggesting that one of the transition mechanisms may underlie regulation of the DegU activity. The expression profiles of DegU-regulated genes differed; flagellar genes and several unknown genes were expressed during the exponential phase, whereas other genes were induced in the stationary phase. The degS mutation did not affect transcription of the flgB-sigD operon, but reduced transcription of sigma(D)-dependent flagellar genes, degU and other DegU-regulated genes. In addition, the degQ mutation did not affect transcription of flagellar genes but reduce transcription of other DegU-regulated genes. Purified DegQ protein stimulated phosphotransfer from phospho-DegS to DegU in vitro. Moreover, DegU binds the promoter region of flgB with a high affinity, whereas DegU binds to the promoter regions of other DegU-regulated genes with a low affinity and in a DegS-dependent manner. Taken together, we propose that a gradual increase in DegU and phospho-DegU levels induces a transition from growth as motile cells to growth as sessile, biofilm-forming cells.