IRON, FUR AND ALGINATE PRODUCTION IN P AERUGINOSA

描述（改编自申请人摘要）：慢性肺部感染 由铜绿假单胞菌发生在囊性纤维化（CF）患者，是 与这种疾病相关的发病率和死亡率的主要原因。 一 与CF相关的铜绿假单胞菌的关键毒力因子是 一种叫做藻酸盐的粘性胞外多糖的过量产生， 临床分离出粘液样表型。 PI最近表示， 粘液性的诱导与sodA的诱导相关，sodA编码 锰超氧化物歧化酶（Mn-SOD）。 引人注目的是，突变体在 sodA（由基因置换产生）是藻酸盐稳定，即使这 表型在野生型细菌中不稳定。 此外，sodA在一个 操纵子与fumC编码TCA循环中的一种脱氢酶，因此这两个基因 在粘液细菌中高度表达。 fumC产生缺陷突变体 在野生型CF分离物中仅观察到40%的藻酸盐。 有趣的是， fumC-sodA操纵子通常只经历转录激活 在缺铁的情况下 这一建议的核心假设是， fumC-sodA操纵子的表达对于优化藻酸盐是重要的 铁缺乏是一个重要因素， 在体内转化为粘液性。 其他研究表明，P. 铁限制连续培养中的铜绿假单胞菌增加了 转化为粘液性。 相反，补充铁盐， 常规培养基引起从粘液性到非粘液性的逆转。 细菌中的许多铁调节基因由Fur（铁摄取）控制 调节蛋白），一种与共识铁盒结合的全局调节剂 这些基因的上游序列，以防止转录。 的 PI已经确定非粘液样铜绿假单胞菌的毛皮突变体产生 Mn-SOD活性升高，表明Fur调节fumC-sodA 操纵子 虽然铁盒子在该地区没有立即 在fumC和sodA之前，操纵子在上游包括至少一个以上的基因 （fagA），并且Fur结合的靶DNA位于那里。 该操纵子 也可能包含更多的下游基因。 总的来说，数据表明， 铁在藻酸盐转化中起重要作用，并且FumC-SodA是 对藻酸盐不稳定性很重要。 从研究中获得的信息 本文提出的将推进目前的知识，这些作用 CF中铜绿假单胞菌感染的发病机制中的因素。

DESCRIPTION (Adapted from the applicant's abstract): Chronic lung infection by P. aeruginosa occurs in patients with cystic fibrosis (CF) and is the leading cause of morbidity and mortality associated with this disease. A critical virulence factor of P. aeruginosa associated with CF is the over-production of a viscous exopolysaccharide called alginate which gives clinical isolates a mucoid phenotype. The PI has recently shown that induction of mucoidy correlates with induction of sodA, which encodes manganese superoxide dismutase (Mn-SOD). Strikingly, mutants defective in sodA (generated by gene replacement) were alginate stable, even though this phenotype is unstable in wild-type bacteria. In addition, sodA is in an operon with fumC encoding a fumarase in the TCA cycle, and thus both genes are highly expressed in mucoid bacteria. Mutants defective in fumC produce only 40% of the alginate seen in the wild-type CF isolate. Interestingly, the fumC-sodA operon normally undergoes transcriptional activation only under iron deprivation. The central hypotheses of this proposal are that expression of the fumC-sodA operon is important for optimal alginate production and that iron deprivation is an important factor in the conversion to mucoidy in vivo. Others have shown that growth of P. aeruginosa in iron-limited continuous culture increases the frequency of conversion to mucoidy. In contrast, supplementation of iron salts to routine culture media causes a reversion from mucoidy to nonmucoidy. Many iron-regulated genes in bacteria are controlled by Fur (ferric uptake regulatory protein), a global regulator that binds to a consensus iron box sequence immediately upstream of these genes to prevent transcription. The PI has established that fur mutants of nonmucoid P. aeruginosa produce elevated Mn-SOD activity, suggesting that Fur regulates the fumC-sodA operon. Although the iron box was absent in the region immediately preceding fumC and sodA, the operon includes at least one more gene upstream (fagA) and the target DNA to which Fur binds is located there. This operon may include more genes downstream as well. Overall, the data suggests that iron plays an important role in alginate conversion and the FumC-SodA are important for alginate instability. Information derived from the studies proposed herein will advance the current knowledge about the role of these factors in the pathogenesis of P. aeruginosa infections in CF.