University of Wisconsin - La Crosse, La Crosse, WI, USA.
University South Alabama College of Medicine, Mobile, AL, USA.
Microbiology (Reading). 2022 Mar;168(3). doi: 10.1099/mic.0.001149.
Uropathogenic (UPEC) cause millions of urinary tract infections each year in the United States. Type 1 pili are important for adherence of UPEC to uroepithelial cells in the human and murine urinary tracts where osmolality and pH vary. Previous work has shown that an acidic pH adversely affects the expression of type 1 pili. To determine if acid tolerance gene products may be regulating gene expression, a bank of K-12 strain acid tolerance gene mutants were screened using , and fusions on single copy number plasmids. We have determined that a mutation in increased transcription of all three genes, suggesting that GadE may be acting as a repressor in a low pH environment. Complementation of the mutation restored gene transcription to wild-type levels. Moreover, mutations in and also affected transcription of the three genes. To verify the role GadE plays in type 1 pilus expression, the NU149 UPEC strain was tested. The mutant had higher gene transcript levels, a higher frequency of Phase-OFF positioning of , and hemagglutination titres that were lower in strain NU149 cultured in low pH medium as compared to the wild-type bacteria. The data demonstrate that UPEC genes are regulated directly or indirectly by the GadE protein and this could have some future bearing on the ability to prevent urinary tract infections by acidifying the urine and shutting off gene expression.
尿路致病性大肠杆菌（UPEC）每年在美国导致数百万人感染尿路感染。1 型菌毛对于 UPEC 在人和鼠类泌尿道中的黏附非常重要，因为泌尿道中的渗透压和 pH 值会发生变化。先前的研究表明，酸性 pH 值会对 1 型菌毛的表达产生不利影响。为了确定酸耐受基因产物是否可能调节基因表达，使用 和 融合蛋白在单拷贝质粒上筛选了 K-12 菌株酸耐受基因突变体库。我们已经确定，gadE 基因突变会增加所有 3 个 基因的转录，表明 GadE 可能在低 pH 环境中作为一种阻遏物发挥作用。gadE 突变的互补恢复了 基因的转录至野生型水平。此外，mutS 和 mutL 突变也影响了这三个 基因的转录。为了验证 GadE 在 1 型菌毛表达中的作用，我们测试了 NU149 UPEC 菌株。与野生型细菌相比，gadE 突变株在低 pH 培养基中培养时，其 基因的转录水平更高，Phase-OFF 定位的频率更高，血凝滴度更低。这些数据表明，UPEC 的 基因直接或间接地受到 GadE 蛋白的调控，这可能对通过酸化尿液和关闭 基因表达来预防尿路感染的能力产生一定的影响。
