Mechanism of RB-to-EB Conversion in Chlamydia

项目总结/摘要 衣原体生殖器感染是美国最常见的感染。 衣原体引起一种不寻常的细胞内感染， 在细菌的分裂形式（网状体或RB）和感染形式之间 （Elementary Body或EB）。RB到EB的转化对于产生感染性 可以将感染传播到新的宿主细胞的后代，但是 规范是未知的。长期以来，人们一直假设衣原体 转换受外在因素调节的领域。然而，我们得到的数据显示， 支持一种新的调节机制，其中RB大小被用作内在因素， 控制转换基于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，我们假设RB 通过连续几轮复制进行大小缩减，并且只能转换 转化为低于大小阈值的EB。在目标1中，我们将通过以下方式测试这种大小控制机制： 确定当RB到EB转换开始的定时被改变时RB大小是否被改变。 变了在目标2中，我们将研究第一个RB的大小是否在启动过程中起作用。 RB大小减小的定时器，其最终在RB到EB转换中达到高潮。在Aim中 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，其中EUO（一种晚期衣原体基因的阻遏物）被滴定掉 以促进转化。在目标4中，我们将研究替代机制 其利用外部信号来控制转换。使用数学建模和3D EM分析，我们将测试一个接触依赖的机制，这是基于接触的 以包涵体膜为外部信号的RB和衣原体 通信机制，其中外部信号由其他通信机制产生。 披衣这些研究将提供重要信息的机制， RB向EB的转化，可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.