CONTROL OF AUTOLYSIS IN PNEUMOCOCCI

描述（由申请人提供）：细菌自溶酶（细胞壁水解酶）的调节是一项高度复杂的生理任务。抗生素如青霉素通过干扰内源性自溶酶的控制来诱导细菌溶解，表明自溶素的主要化学治疗相关性。虽然抗生素与细胞壁合成酶的结合已经得到很好的表征，但尚不清楚这一事件如何导致自溶酶的失调。这是这方面的抗生素活性，揭示为耐受表型，这是本建议的重点。 对青霉素有反应而停止生长，但不能裂解而死亡的细菌称为耐青霉素细菌。这种特性首先在肺炎球菌中描述，确保细菌存活，并且是大多数菌株发展抗生素耐药性的第一步。在该提议的前5年期间，鉴定了5个遗传位点，当在肺炎球菌中突变时，其产生耐受性。这些是在自溶级联中鉴定的第一批成员。两个位点定义了一个信号转导装置触发自溶。这一建议旨在通过详细描述导致溶解的信号转导机制来建立这些发现。特别是，将阐明死亡肽信号的结构和代谢，并表征潜在的第二肽信号。为了鉴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进行详细研究。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，将通过改进对该性状的诊断和研究耐受性对动物模型感染过程的影响来定义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，并可能表明为什么临床环境中的细菌在面对抗生素压力时选择调节自溶活性而不是放弃自杀性自溶素。

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.