The curli biosynthesis regulator CsgD co-ordinates the expression of both positive and negative determinants for biofilm formation in Escherichia coli
The curli biosynthesis regulator CsgD co-ordinates the expression of both positive and negative determinants for biofilm formation in Escherichia coli
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DOI：
10.1099/mic.0.26306-0
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发表时间：
2003-10-01
期刊：
影响因子：
2.8
通讯作者：
Landini, P
中科院分区：
文献类型：
--
作者：
Brombacher, E;Dorel, C;Landini, P
curli的产生是生物膜形成的重要细胞外结构，受OmpR的正调控，OmpR与EnvZ蛋白一起构成渗透压敏感双组分调控系统。由于缺乏csgD表达，curli的表达在大多数大肠杆菌实验室菌株如MG 1655中是隐蔽的。csgD基因编码卷曲亚基编码csgBA操纵子的转录激活因子。ompR 234上调突变可以恢复csgD表达，导致curli产生和增加的生物膜形成。在这份报告中，它表明，ompR 234依赖csgD的表达，除了在生长的稳定期csgBA激活，刺激yaiC基因的表达和负调控至少两个其他基因，pepD和yagS。这四个基因的启动子区共享一个保守的11 bp序列（CGGGKGAKNKA），这是CsgD调控csgBA和yaiC所必需的。虽然在csgBA和yaiC启动子中，该序列都位于启动子元件的上游，但在yagS和pepD中，它与推定的-10序列或转录起始点重叠，表明CsgD既可以作为激活子又可以作为阻遏子。粘附实验表明，来自多拷贝质粒的yagS和pepD的csgD非依赖性表达对生物膜形成产生负面影响，相反，生物膜形成受到yaiC表达的刺激。因此，CsgD刺激E.通过同时激活粘附阳性决定子（编码curli的csg操纵子和yaiC基因的产物）和抑制阴性效应子如yagS和pepD来抑制大肠杆菌。
Production of curli, extracellular structures important for biofilm formation, is positively regulated by OmpR, which constitutes with the EnvZ protein an osmolarity-sensing two-component regulatory system. The expression of curli is cryptic in most Escherichia coli laboratory strains such as MG1655, due to the lack of csgD expression. The csgD gene encodes a transcription activator of the curli-subunit-encoding csgBA operon. The ompR234 up-mutation can restore csgD expression, resulting in curli production and increased biofilm formation. In this report, it is shown that ompR234-dependent csgD expression, in addition to csgBA activation during stationary phase of growth, stimulates expression of the yaiC gene and negatively regulates at least two other genes, pepD and yagS. The promoter regions of these four genes share a conserved 11 bp sequence (CGGGKGAKNKA), necessary for csgBA and yaiC regulation by CsgD. While at both the csgBA and yaiC promoters the sequence is located upstream of the promoter elements, in both yagS and pepD it overlaps either the putative -10 sequence or the transcription start point, suggesting that CsgD can function as both an activator and a repressor. Adhesion experiments show that csgD-independent expression of both yagS and pepD from a multicopy plasmid negatively affects biofilm formation, which, in contrast, is stimulated by yaiC expression. Thus it is proposed that CsgD stimulates biofilm formation in E. coli by contemporary activation of adhesion positive determinants (the curli-encoding csg operons and the product of the yaiC gene) and repression of negative effectors such as yagS and pepD.