Hirakawa Hidetada, Shimokawa Mizuki, Noguchi Koshi, Tago Minori, Matsuda Hiroshi, Takita Ayako, Suzue Kazutomo, Tajima Hirotaka, Kawagishi Ikuro, Tomita Haruyoshi
Department of Bacteriology, Graduate School of Medicine, Gunma University, Maebashi, Gunma, Japan.
Department of Infectious Diseases and Host Defense, Graduate School of Medicine, Gunma University, Maebashi, Gunma, Japan.
Front Microbiol. 2023 Jul 18;14:1185804. doi: 10.3389/fmicb.2023.1185804. eCollection 2023.
Uropathogenic (UPEC) is a major causative agent of urinary tract infections. The bacteria internalize into the uroepithelial cells, where aggregate and form microcolonies. UPEC fimbriae and flagella are important for the formation of microcolonies in uroepithelial cells. PapB/FocB family proteins are small DNA-binding transcriptional regulators consisting of approximately 100 amino acids that have been reported to regulate the expression of various fimbriae, including P, F1C, and type 1 fimbriae, and adhesins. In this study, we show that TosR, a member of the PapB/FocB family is the activator of flagellar expression. The mutant had similar expression levels of type 1, P and F1C fimbriae as the parent strain, but flagellar production was markedly lower than in the parent strain. Flagellin is a major component of flagella. The gene encoding flagellin, , is transcriptionally activated by the sigma factor FliA. The expression is induced by the flagellar master regulator FlhDC. The and genes form an operon. The promoter activity of and in the mutant was significantly lower than in the parent strain. The purified recombinant TosR does not bind to and but to the upstream region of the gene. TosR is known to bind to an AT-rich DNA sequence consisting of 29 nucleotides. The characteristic AT-rich sequence exists 550-578 bases upstream of the gene. The DNA fragment lacking this sequence did not bind TosR. Furthermore, loss of the gene reduced motility and the aggregation ability of UPEC in urothelial cells. These results indicate that TosR is a transcriptional activator that increases expression of the operon genes, contributing to flagellar expression and optimal virulence.
尿路致病性大肠杆菌（UPEC）是尿路感染的主要病原体。这种细菌会内化进入尿道上皮细胞，并在其中聚集形成微菌落。UPEC的菌毛和鞭毛对于在尿道上皮细胞中形成微菌落很重要。PapB/FocB家族蛋白是由大约100个氨基酸组成的小型DNA结合转录调节因子，据报道可调节包括P菌毛、F1C菌毛和1型菌毛以及黏附素在内的各种菌毛的表达。在本研究中，我们表明PapB/FocB家族成员TosR是鞭毛表达的激活因子。该突变体与亲本菌株相比，1型、P菌毛和F1C菌毛的表达水平相似，但鞭毛的产生明显低于亲本菌株。鞭毛蛋白是鞭毛的主要成分。编码鞭毛蛋白的基因fljB由sigma因子FliA转录激活。fljB的表达由鞭毛主调节因子FlhDC诱导。fljB和fljC基因形成一个操纵子。fljB和fljC在突变体中的启动子活性明显低于亲本菌株。纯化的重组TosR不与fljB和fljC结合，但与fljC基因的上游区域结合。已知TosR与一个由29个核苷酸组成的富含AT的DNA序列结合。该富含AT的特征序列存在于fljC基因上游550 - 578个碱基处。缺乏该序列的DNA片段不与TosR结合。此外，fljC基因的缺失降低了UPEC在尿道上皮细胞中的运动性和聚集能力。这些结果表明，TosR是一种转录激活因子，可增加fljB操纵子基因的表达，有助于鞭毛表达和最佳毒力。
