Department of Epidemiology, University of Michigan School of Public Health, Michigan, USA.
Infect Immun. 2012 Jun;80(6):1969-79. doi: 10.1128/IAI.00043-12. Epub 2012 Apr 2.
Type 1 fimbriae and flagella, two surface organelles critical for colonization of the urinary tract by uropathogenic Escherichia coli (UPEC), mediate opposing virulence objectives. Type 1 fimbriae facilitate adhesion to mucosal cells and promote bacterial persistence in the urinary tract, while flagella propel bacteria through urine and along mucous layers during ascension to the upper urinary tract. Using a transposon screen of the E. coli CFT073 fim locked-ON (L-ON) mutant, a construct that constitutively expresses type 1 fimbriae and represses motility, we identified six mutants that exhibited a partial restoration of motility. Among these six mutated genes was mutS, which encodes a component of the methyl-directed mismatch repair (MMR) system. When complemented with mutS in trans, motility was again repressed. To determine whether the MMR system, in general, is involved in this reciprocal control, we characterized the effects of gene deletions of other MMR components on UPEC motility. Isogenic deletions of mutS, mutH, and mutL were constructed in both wild-type CFT073 and fim L-ON backgrounds. All MMR mutants showed an increase in motility in the wild-type background, and ΔmutH and ΔmutS mutations increased motility in the fim L-ON background. Cochallenge of the wild-type strain with an MMR-defective strain showed a subtle but significant competitive advantage in the bladder and spleen for the MMR mutant using the murine model of ascending urinary tract infection after 48 h. Our findings demonstrate that the MMR system generally affects the reciprocal regulation of motility and adherence and thus could contribute to UPEC pathogenesis during urinary tract infections.
1 型菌毛和鞭毛是尿路感染性大肠杆菌（UPEC）定植尿路所必需的两种表面器官，介导相反的毒力目标。1 型菌毛促进与黏膜细胞的黏附，并促进细菌在尿路中的持续存在，而鞭毛则在细菌向上尿路上升时推动细菌通过尿液并沿着黏液层移动。我们使用大肠杆菌 CFT073 fim 锁定 ON（L-ON）突变体的转座子筛选，构建了一种持续表达 1 型菌毛并抑制运动的突变体，发现了六个表现出部分运动恢复的突变体。在这六个突变基因中，有 mutS，它编码甲基指导的错配修复（MMR）系统的一个组成部分。当与 mutS 在反式中互补时，运动再次受到抑制。为了确定 MMR 系统是否普遍参与这种相互控制，我们研究了其他 MMR 组件基因缺失对 UPEC 运动性的影响。在野生型 CFT073 和 fim L-ON 背景下构建了 mutS、mutH 和 mutL 的同源缺失突变体。所有 MMR 突变体在野生型背景下的运动性增加，而 ΔmutH 和 ΔmutS 突变在 fim L-ON 背景下增加了运动性。用鼠类上行尿路感染模型在 48 小时后对野生型菌株与 MMR 缺陷菌株进行共感染，野生型菌株与 MMR 缺陷菌株的竞争优势在膀胱和脾脏中都很明显，但不显著。我们的研究结果表明，MMR 系统通常会影响运动性和黏附性的相互调节，因此可能会影响尿路感染期间 UPEC 的发病机制。
