D-serine/DsdCXA control of E. coli uropathogenesis

大肠杆菌是社区获得性尿路感染最常见的原因 (UTI)也是医院内尿路感染和败血症的主要原因我们关注的是一种基因 在大肠杆菌尿脓毒症菌株CFT 073中argW处的岛，其含有用于D- 丝氨酸利用和ipuAB，fimBE的同源物，1型菌毛相位开关 重组酶缺乏D-丝氨酸脱氨酶的CFT 073 dsdA突变体比正常人高300倍。 与野生型CFT 073相比，CFT 073在实验小鼠的膀胱或肾脏中具有竞争力。 感染的老鼠与CFT 073相比，分别有44个和41个基因表达上调和下调- 在鼠UTI期间在CFT 073 dsdA突变体中调节。上调基因编码P 和F1 C菌毛，溶血素，OmpF，二肽转运蛋白DppA，和几个基因， 未知的功能CFT 073以及其它尿路致病性E.大肠杆菌显示（+）趋化性 D-丝氨酸，而不是L-丝氨酸，如E的情况。大肠杆菌K-12。ipuA具有类似fimB的ON至OFF 和鼠UTI期间OFF至ON fimS转换活性。A CFT073 dsdA：：lacZ 转录融合经历可逆的相位转换，尽管是通过一个未识别的 ipuA和ipuB突变影响的机制。ipuA和ipuB还控制fimS， 一组编码分泌产物的基因的独立可逆相位转换， 包括溶血素。因此，我们对最初的假设产生了强有力的支持 D-丝氨酸代表调节CFT 073毒力基因的重要信号， 生长在尿路和dsdCXA连接的重组酶介导的相态 除了1型菌毛外，重要的尿毒力和适应性因子的调节。我们将 研究细胞内D-丝氨酸升高导致细胞内 urovirulence和fitness基因，并表征fimS以外的基因座， 重组酶我们将使用CFT 073 dsdA突变体作为DsdA OFF状态的模型 研究P菌毛和溶血素在小鼠膀胱移行细胞中的作用， 肾本研究的目的是鉴定和鉴定大肠杆菌的毒力基因。杆菌 与严重的人类疾病有关。这项工作将有助于开发新的疫苗， 抗菌剂为此，我们最近获得的证据表明， 脱氨酶可作为鉴定新抗微生物剂的新药物靶标。

Escherichia coli is the most common cause of community-acquired urinary tract infection (UTI) and a leading cause of nosocomial UTIs and sepsis. We have focused on a genetic island at argW in E.coli urosepsis strain CFT073 which contains the dsdCXA genes for D- serine utilization and ipuAB, homologs of fimBE, the type 1 fimbriae phase-switch recombinases. A CFT073 dsdA mutant lacking D-serine deaminase is 300-fold more competitive than wild type CFT073 in colonizing the bladder or kidney of experimentally infected mice. Compared to CFT073, 44 and 41 genes were respectively up- and down- regulated in the CFT073 dsdA mutant during murine UTI. Up-regulated genes encoded P and F1C fimbriae, hemolysin, OmpF, a dipeptide transporter DppA, and several genes with unknown functions. CFT073 as well as other uropathogenic E. coli show (+) chemotaxis toward D-serine, but not L-serine as is the case E. coli K-12. ipuA has fimB-like ON-to-OFF and OFF-to-ON fimS switching activity during murine UTI. A CFT073 dsdA::lacZ transcriptional fusion undergoes reversible phase-switching albeit by an unidentified mechanism affected by ipuA and ipuB mutations. ipuA and ipuB also control a fimS- independent reversible phase switch of a set of genes encoding secreted products that includes the hemolysin. Therefore, we generated strong support of our original hypotheses that D-serine represents an important signal for regulation of CFT073 virulence genes and growth in the urinary tract and that the dsdCXA-linked recombinases mediate phase-state regulation of important urovirulence and fitness factors besides the type 1 fimbriae. We will investigate the mechanism whereby elevated intracellular D-serine leads to up-regulation of urovirulence and fitness genes and characterize loci aside from fimS that are controlled by the recombinases. We will use the CFT073 dsdA mutant as a model of the DsdA OFF state to study the roles of P fimbriae and hemolysin in colonization of the murine bladder and kidney. The objective of our project is to identify and characterize virulence genes for E. coli involved in serious human diseases. This work will aid development of new vaccines and antimicrobials. To that end, we have recently acquired evidence that the D-serine deaminase can serve as a novel drug target for identification of new antimicrobials.