CONTROL OF AUTOLYSIS IN PNEUMOCOCCI

描述(由申请人提供)：调节细菌自溶酶(细胞壁水解酶)是一项高度复杂的生理任务。青霉素等抗生素通过干扰内源性自溶酶的控制来诱导细菌溶解，表明自溶素与化疗有关。虽然抗生素与细胞壁合成酶的结合已经被很好地表征，但这一事件如何导致自溶酶的解除调节尚不清楚。正是抗生素活性的这一方面，表现为耐受表型，这是本提案的重点。 对青霉素有反应而停止生长，但不能溶解并死亡的细菌称为耐受性细菌。这一特性最先在肺炎球菌中被描述，它确保了细菌的生存，也是大多数菌株产生抗生素耐药性的第一步。在这项建议的前5年中，在肺炎球菌中发现了5个产生耐受性的遗传位点。这些是在自溶级联中发现的第一批成员。其中两个基因座定义了触发自溶的信号转导装置。这项建议试图通过详细描述导致溶解的信号转导机制来建立在这些发现的基础上。特别是，死亡肽信号的结构和新陈代谢将被阐明，并将描述潜在的第二肽信号。为了确定自溶级联中的更多元素，将采取两种方法。另外两个耐受突变体将被详细研究。其次，将寻找受VncR DNA结合蛋白影响的VncR调节子中的元件。最后，将通过改进对这一特征的诊断并在动物模型中调查耐受性对感染过程的影响来确定耐受性在临床环境中的意义。这将为开发新的潜在抗菌剂提供重要信息，并可能暗示为什么临床环境中的细菌在面临抗生素压力时选择调节自溶活性，而不是放弃自杀的自溶素。

DESCRIPTION (provided by applicant):Regulation of bacterial autolytic enzymes (cell wall hydrolases) is a highly sophisticated physiological task. Antibiotics such as penicillin induce bacteriolysis by interfering with the control of the endogenous autolytic enzymes, indicating the major chemotherapeutic relevance of autolysins. Although the binding of antibiotics to cell wall synthetic enzymes has been very well characterized, it is unknown how this event leads to deregulation of autolytic enzymes. It is this aspect of antibiotic activity, revealed as the tolerant phenotype, that is the focus of this proposal. Bacteria which stop growing in response to penicillin but fail to lyse and die are termed tolerant. This property, first described in pneumococcus, ensures bacterial survival and is the first step for most strains on the way to development of antibiotic resistance. During the first 5 years of this proposal, 5 genetic loci were identified which produced tolerance when mutated in pneumococcus. These are the first members identified in an autolytic cascade. Two of the loci defined a signal transduction apparatus triggering autolysis. This proposal seeks to build on these findings by characterizing in detail the mechanism of signal transduction which results in lysis. In particular, the structure and metabolism of the death peptide signal will be elucidated and a potential second peptide signal will be characterized. To identify more elements in the autolysis cascade, two approaches will be taken. Two additional tolerant mutants will be studied in detail. Second, elements in the VncR regulon affected by the VncR DNA binding protein will be sought. Finally, the significance of tolerance in the clinical setting will be defined by improving diagnostics for this trait and investigating the impact of tolerance on the course of infection in animal models. This will provide information important to the development of new potential antibacterial agents and perhaps suggest why bacteria in the clinical environment choose to regulate autolytic activity rather than dispense with suicidal autolysins in the face of antibiotic pressure.