Role of phase-variable DNA methylase in virulence of Haemophilus influenzae

摘要 流感嗜血杆菌是人类正常菌群中的一员。 鼻咽部。它也是引起上呼吸道感染的原因之一，如中耳炎和 支气管炎和全身性感染，如菌血症和脑膜炎。理想情况下，预防或治疗 流感嗜血杆菌疾病只会影响与疾病相关的细菌，而不会扰乱正常的菌群。这个 这项工作的长期目标是了解从无症状的定植到粘膜或 全身感染。我们假设鼻咽部细菌适应的机制之一 对于一个新的环境，如中耳或血液，是DNA甲基酶的相变 吉恩，莫德。外膜蛋白和脂多糖等表面结构的相变 已经在流感嗜血杆菌中研究了几年。Mod基因含有一个类似的串联重复区域 与流感嗜血杆菌中其他特征良好的相变基因中发现的那些不同，但具有生理作用 MOD的相变直到最近才为人所知。我们的合作者比较了一个mod缺失突变体 通过微阵列分析发现，mod影响至少15个基因的转录。 (Srikhanta等人)2005 PNA 102：5547-51)显然是通过启动子的甲基化。并不是所有这些基因 都有已知的功能，但通常由mod表达上调的基因与营养有关 而mod表达下调的基因中有几个属于热休克组。它是 提出了MOD的相变是一种随机、协调的开关机制 其他基因。这些研究使用了实验室适应的无毒菌株RD KW20。相变模式 在临床分离的流感嗜血杆菌和其他粘膜生物中也发现了基因，如 脑膜炎奈瑟菌。本探索性项目将研究这一新的毒力基因调控机制。 流感嗜血杆菌， (I)使用基因芯片识别临床分离株中与MOD相关的基因，以及 (Ii)研究MOD阶段在实验性感染中的作用。 发现MOD调控在临床分离株中普遍存在，并影响其致病机制，将为 未来关于细菌对人体内不同解剖生态位的生理适应的研究。

Abstract Haemophilus influenzae is a member of the normal bacterial flora colonizing the human nasopharynx. It is also a cause of infections of the upper respiratory tract, such as otitis media and bronchitis, and of systemic infections, such as bacteremia and meningitis. Ideally, prevention or treatment of H. influenzae disease would affect only disease-associated bacteria without perturbing normal flora. The long-term goal of this work is to understand the transition from asymptomatic colonization to mucosal or systemic infection. We hypothesize that one of the mechanisms by which nasopharyngeal bacteria adapt to a new environment such as the middle ear or the bloodstream is phase variation of a DNA methylase gene, mod. Phase variation of surface structures such as outer membrane proteins and lipopolysaccharide has been studied in H. influenzae for several years. The mod gene contains a tandem repeat region similar to those identified in other, well-characterized phase-variable genes in H. influenzae, but a physiologic role for mod phase variation was unknown until recently. Our collaborators compared a mod deletion mutant with a mod+ parent by microarray analysis and reported that mod affects transcription of at least 15 genes (Srikhanta et al. 2005 PNAS 102:5547-51) apparently via methylation of promoters. Not all of these genes have known functions, but generally genes upregulated by mod expression are involved in nutrient acquisition, while several of those downregulated by mod expression are in the heat-shock group. It is proposed that phase variation of mod is a mechanism for random, coordinated on/off switching of several other genes. These studies used the laboratory-adapted, avirulent strain Rd KW20. Phase-variable mod genes have also been identified in clinical isolates of H. influenzae and in other mucosal organisms such as Neisseria meningitidis. This exploratory project will study this novel mechanism of gene regulation in virulent H. influenzae, (i) using microarrays to identify mod-related genes in clinical isolates and (ii) examining the effect of mod phase in experimental infections. Finding that mod regulation is common in clinical isolates and affects pathogenesis will provide the basis for future studies on the physiological adaptation of bacteria to different anatomic niches within the human host.