IRON, FUR AND ALGINATE PRODUCTION IN P AERUGINOSA

描述(改编自申请人的摘要)：慢性肺部感染 由铜绿假单胞菌引起的囊性纤维化(CF)患者是 与这种疾病相关的发病率和死亡率的主要原因。一个 与铜绿假单胞菌相关的临界毒力因子是 过量生产一种名为海藻酸盐的粘性胞外多糖，它能提供 临床分离出一种粘液表型。国际刑事法院最近表明， 粘液样物质的诱导与苏打的诱导有关，苏打编码 锰超氧化物歧化酶(Mn-SOD)。令人惊讶的是，变种人在 苏打水(由基因置换产生)是海藻酸盐稳定的，即使这 野生型细菌的表型不稳定。此外，苏打水还在一个 在TCA循环中带有编码富马酸酶的fumC的操纵子，因此这两个基因 在粘液性细菌中高度表达。FumC生产中存在缺陷的突变株 只有40%的藻酸盐出现在野生型CF分离物中。有趣的是， FumC-Soda操纵子通常只经历转录激活 在缺铁状态下。这项提议的中心假设是 FumC-Soda操纵子的表达对最适藻酸盐很重要 生产和铁缺乏是一个重要的因素 在体内转化为粘液样。另一些研究表明，P。 铜绿假单胞菌在铁限制的连续培养中增加了 转化为粘液性。相比之下，补充铁盐到 常规培养基使粘液性向非粘液性逆转。 细菌中许多铁调节基因受Fur(铁摄取)控制 调控蛋白)，一个绑定到共识铁盒的全球调控者 直接在这些基因的上游测序，以防止转录。这个 PI已经证实，非粘液性铜绿假单胞菌的毛皮突变株产生 锰-超氧化物歧化酶活性升高，提示毛皮对碳水化合物有调节作用 歌剧。尽管该地区立即没有了铁箱 在fumC和苏打水之前，操纵子至少还包括一个上游基因 (Faga)，毛发结合的目标DNA位于那里。这个操纵器 也可能包括更多下游基因。总体而言，数据表明 铁在海藻酸盐转化中起着重要作用，富碳苏打是 对藻酸盐不稳定很重要。从研究中获得的信息 在此提出的建议将促进对这些角色的当前了解 铜绿假单胞菌感染的致病因素。

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.