Department of Microbiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9048, USA.
J Bacteriol. 2011 Dec;193(24):6843-51. doi: 10.1128/JB.06141-11. Epub 2011 Oct 7.
Enterohemorrhagic Escherichia coli O157:H7 (EHEC) causes bloody diarrhea and hemolytic-uremic syndrome. EHEC encodes the sRNA chaperone Hfq, which is important in posttranscriptional regulation. In EHEC strain EDL933, Hfq acts as a negative regulator of the locus of enterocyte effacement (LEE), which encodes most of the proteins involved in type III secretion and attaching and effacing (AE) lesions. Here, we deleted hfq in the EHEC strain 86-24 and compared global transcription profiles of the hfq mutant and wild-type (WT) strains in exponential growth phase. Deletion of hfq affected transcription of genes common to nonpathogenic and pathogenic strains of E. coli as well as pathogen-specific genes. Downregulated genes in the hfq mutant included ler, the transcriptional activator of all the LEE genes, as well as genes encoded in the LEE2 to -5 operons. Decreased expression of the LEE genes in the hfq mutant occurred at middle, late, and stationary growth phases. We also confirmed decreased regulation of the LEE genes by examining the proteins secreted and AE lesion formation by the hfq mutant and WT strains. Deletion of hfq also caused decreased expression of the two-component system qseBC, which is involved in interkingdom signaling and virulence gene regulation in EHEC, as well as an increase in expression of stx(2AB), which encodes the deadly Shiga toxin. Altogether, these data indicate that Hfq plays a regulatory role in EHEC 86-24 that is different from what has been reported for EHEC strain EDL933 and that the role of Hfq in EHEC virulence regulation extends beyond the LEE.
产肠毒素性大肠杆菌 O157：H7（EHEC）可引起血性腹泻和溶血尿毒综合征。EHEC 编码 sRNA 伴侣 Hfq，该伴侣在转录后调控中发挥重要作用。在 EHEC 菌株 EDL933 中，Hfq 作为肠上皮细胞脱落（LEE）基因座的负调控因子，该基因座编码大多数涉及 III 型分泌和附着及脱落（AE）病变的蛋白质。在这里，我们在 EHEC 菌株 86-24 中删除了 hfq，并比较了指数生长期 hfq 突变株和野生型（WT）菌株的全局转录谱。hfq 缺失影响了非致病性和致病性大肠杆菌菌株以及病原体特异性基因的共同基因的转录。hfq 突变体中下调的基因包括 ler，所有 LEE 基因的转录激活子，以及 LEE2 到-5 操纵子编码的基因。在 hfq 突变体中，LEE 基因的表达在中、晚期和静止期减少。我们还通过检查 hfq 突变体和 WT 菌株分泌的蛋白质和 AE 病变形成，证实了 LEE 基因的下调调节。hfq 缺失还导致涉及 EHEC 种间信号传递和毒力基因调节的双组分系统 qseBC 的表达减少，以及编码致命志贺毒素的 stx(2AB)的表达增加。总的来说，这些数据表明 Hfq 在 EHEC 86-24 中发挥的调节作用与 EHEC 菌株 EDL933 报道的不同，并且 Hfq 在 EHEC 毒力调节中的作用不仅限于 LEE。
