Regulation of type 1 fimbriae synthesis and biofilm formation by the transcriptional regulator LrhA of Escherichia coli
Regulation of type 1 fimbriae synthesis and biofilm formation by the transcriptional regulator LrhA of Escherichia coli
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DOI：
10.1099/mic.0.28098-0
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发表时间：
2005-10-01
期刊：
影响因子：
2.8
通讯作者：
Unden, G
中科院分区：
文献类型：
--
作者：
Blumer, C;Kleefeld, A;Unden, G
大肠杆菌的1型菌毛有助于附着于宿主粘膜并促进非生物表面上的生物膜形成。转录调节因子LrhA是鞭毛、运动和趋化基因的阻遏物，调节1型菌毛的生物膜形成和表达。全基因组表达谱分析表明，lrhA的失活导致1型菌毛的结构成分的表达增加。在体外，LrhA结合到两个fim重组酶（FimB和FimE）的启动子区域，催化fimA启动子的反转，并结合到可逆元件本身。翻译lacZ融合这些基因和fimE转录水平的定量实时PCR表明，LrhA影响1型菌毛相位变化，主要是通过激活FimE，这是所需的fim开关的ON-到-OFF转换。通过酵母细胞的甘露糖敏感性凝集证实了由于lrhA破坏而增强的1型菌毛表达。生物膜的形成受到lrhA失活的刺激，并在LrhA过量生产时完全抑制。LrhA对生物膜形成的影响是通过改变表面分子的水平来实现的，最可能的是鞭毛和1型菌毛。总之，数据显示LrhA作为1型菌毛表达的阻遏物的作用，并且因此作为生物膜发育的初始阶段的调节剂，并且推测还作为细菌粘附于上皮宿主细胞的调节剂。
Type 1 fimbriae of Escherichia coli facilitate attachment to the host mucosa and promote biofilm formation on abiotic surfaces. The transcriptional regulator LrhA, which is known as a repressor of flagellar, motility and chennotaxis genes, regulates biofilm formation and expression of type 1 fimbriae. Whole-genome expression profiling revealed that inactivation of lrhA results in an increased expression of structural components of type 1 fimbriae. In vitro, LrhA bound to the promoter regions of the two fim recombinases (FimB and FimE) that catalyse the inversion of the fimA promoter, and to the invertible element itself. Translational lacZ fusions with these genes and quantification of fimE transcript levels by real-time PCR showed that LrhA influences type 1 fimbrial phase variation, primarily via activation of FimE, which is required for the ON-to-OFF transition of the fim switch. Enhanced type 1 fimbrial expression as a result of lrhA disruption was confirmed by mannose-sensitive agglutination of yeast cells. Biofilm formation was stimulated by lrhA inactivation and completely suppressed upon LrhA overproduction. The effects of LrhA on biofilm formation were exerted via the changed levels of surface molecules, most probably both flagella and type 1 fimbriae. Together, the data show a role for LrhA as a repressor of type 1 fimbrial expression, and thus as a regulator of the initial stages of biofilm development and, presumably, bacterial adherence to epithelial host cells also.