Mechanism of RB-to-EB Conversion in Chlamydia

项目摘要/摘要 衣原体感染是美国最常见的报告感染。 衣原体引起一种不寻常的细胞内感染，在这种感染中有 在细菌的分裂形式(网状小体或RB)和传染性形式之间 (基本体或EB)。RB到EB的转换是产生传染性的关键 可以将感染传播到新的宿主细胞的后代，但 监管它是未知的。衣原体有一个由来已久的假设 换算受外部因素控制的字段。然而，我们已经获得了数据 支持将RB大小作为内在因素的新监管机制 控制转换。基于对衣原体大小和数量的时间测量 通过三维电子显微镜(3D EM)获得的，我们假设RBS 通过连续几轮复制进行大小缩减，并且只能转换为 到低于尺寸阈值的EB。在目标1中，我们将通过以下方式测试此大小控制机制 确定当RB到EB转换开始的定时为 变化。在目标2中，我们将调查第一个RB的大小是否在开始时起作用 RB大小减小的计时器，最终导致RB到EB的转换。在AIM 3，我们将研究如何使用RB大小来调节转换。我们提出了一个 一种滴定机制，在该机制中，衣原体晚期基因的抑制因子EuO被滴定 在规模较小的苏格兰皇家银行推动转换。在目标4中，我们将研究替代机制 利用外部信号来控制转换。使用数学建模和3D EM分析，我们将测试一种基于接触的接触依赖机制 以包涵膜为外信号的RB和衣原体 一种通信机制，其中外部信号由其他人产生 衣原体。这些研究将提供重要的信息，以了解其机制。 Rb到EB的转换，可以应用于新的治疗策略，以阻断 发育周期和感染性后代的产生。

Project Summary/Abstract Chlamydia genital infections are the most commonly reported infection in the U.S. All Chlamydia species cause an unusual intracellular infection in which there is conversion between a dividing form of the bacterium (reticulate body or RB) and the infectious form (elementary body or EB). RB-to-EB conversion is critical for producing infectious progeny that can spread the infection to a new host cell, but the mechanisms that regulate it are unknown. There has been a longstanding assumption in the Chlamydia field that conversion is regulated by an extrinsic factor. However, we have obtained data to support a new regulatory mechanism in which RB size is used as an intrinsic factor to control conversion. Based on temporal measurements of chlamydial size and number obtained with three-dimensional electron microscopy (3D EM), we hypothesize that RBs undergo size reduction through successive rounds of replication and can only convert into an EB below a size threshold. In Aim 1, we will test this size control mechanism by determining whether RB size is altered when the timing of RB-to-EB conversion onset is changed. In Aim 2, we will investigate if the size of the first RB plays a role in starting the timer of RB size reduction that eventually culminates in RB-to-EB conversion. In Aim 3, we will study how RB size could be used to regulate conversion. We propose a titration mechanism in which EUO, a repressor of late chlamydial genes, is titrated away in smaller RBs to promote conversion. In Aim 4, we will study alternative mechanisms that utilize extrinsic signals to control conversion. Using mathematical modeling and 3D EM analysis, we will test a contact-dependent mechanism, which is based on contact of the RB with the inclusion membrane as the external signal, and a chlamydial communication mechanism in which the external signal is produced by other chlamydiae. These studies will provide important information about the mechanism of RB-to-EB conversion that can be applied in new therapeutic strategies to block the developmental cycle and the production of infectious progeny.