Sjöström Annika E, Balsalobre Carlos, Emödy Levente, Westerlund-Wikström Benita, Hacker Jörg, Uhlin Bernt Eric
Department of Molecular Biology and Laboratory for Molecular Infection Medicine Sweden, Umeå University, S-90187 Umeå, Sweden.
Microb Pathog. 2009 May;46(5):243-52. doi: 10.1016/j.micpath.2009.01.007. Epub 2009 Feb 4.
The genomes of pathogenic Escherichia coli may contain several different fimbrial operons. How bacteria regulate and coordinate the choice of fimbrial expression under different circumstances remains largely unanswered. In this report we have investigated the role of the sfaX(II) gene associated to the Sfa(II) fimbrial determinant in the E. coli isolate IHE3034. sfaX(II) belongs to a subfamily of genes, the 17k Da genes, located near different fimbrial operons in uropathogenic and newborn meningitis E. coli (NMEC) strains. Using the NMEC isolate IHE3034 and non-pathogenic E. coli strains we found that the sfaX(II) gene had an inhibitory effect on type 1 fimbriae expression. Down-regulation of type 1 fimbriae was exerted at transcriptional level both by inhibiting expression from the fimA promoter and by reducing the frequency of OFF-to-ON switching. The effect of sfaX(II) on expression of the recombinase FimB that catalyzes OFF-to-ON switching might explain the described reduction in percentage of ON cells. Moreover, expression of the sfaX(II) gene strongly influenced motility and flagella production of the NMEC isolate IHE3034. We propose that the sfaX(II) gene, and presumably other members in the 17 kDa gene family, may play a role in the control of virulence related gene expression in pathogenic E. coli.
致病性大肠杆菌的基因组可能包含几个不同的菌毛操纵子。在不同情况下，细菌如何调节和协调菌毛表达的选择在很大程度上仍未得到解答。在本报告中，我们研究了与大肠杆菌分离株IHE3034中Sfa（II）菌毛决定簇相关的sfaX（II）基因的作用。sfaX（II）属于一个基因亚家族，即17kDa基因，位于尿路致病性大肠杆菌和新生儿脑膜炎大肠杆菌（NMEC）菌株中不同菌毛操纵子附近。使用NMEC分离株IHE3034和非致病性大肠杆菌菌株，我们发现sfaX（II）基因对1型菌毛表达具有抑制作用。1型菌毛的下调是通过抑制fimA启动子的表达和降低从关闭到开启转换的频率在转录水平上发挥作用的。sfaX（II）对催化从关闭到开启转换的重组酶FimB表达的影响可能解释了所描述的开启细胞百分比的降低。此外，sfaX（II）基因的表达强烈影响了NMEC分离株IHE3034的运动性和鞭毛产生。我们提出，sfaX（II）基因以及大概17kDa基因家族中的其他成员可能在致病性大肠杆菌毒力相关基因表达的控制中发挥作用。
