GENETICS OF MYXOPHAGES

富含G+ C的温和噬菌体Mx 8基因组的序列显示，它与迄今为止详细检查的任何噬菌体都不同。我们对Mx 8基因及其功能的持续研究将可能揭示其M. xanthus宿主在多细胞发育过程中。我们将试图揭示一个独特的噬菌体-宿主适应的秘密：Mx 8原噬菌体是如何在整个M. xanthus多细胞的发展，尽管戏剧性的，连续的，全球性的变化，基因调控发生在这个周期？我们将完成剩余的50 kb Mx 8基因组的三分之一的序列，以确定Mx 8基因参与溶原性发展，裂解发展，和Mx 8原噬菌体的稳定性在整个多细胞发育周期的主机。 一对不同的Mx 8启动子的结构和功能将被解剖，以了解哪些序列元件对M中强启动子功能至关重要。xanthus 将使用单拷贝质粒捕获营养M。xanthus启动子，以暴露它们的共有序列元件。 噬菌体启动子将被克隆，以了解它们在噬菌体生长的裂解周期中何时被激活，或者在M.溶原黄杆菌将在控制Mx 8超感染免疫的基因中进行突变，以了解其新的剂量依赖性机制，在阻遏物基因中进行突变，以允许来自强Mx 8启动子的基因的诱导表达，并在噬菌体末端酶中进行突变，以构建高频广义转导突变体。 温度敏感的突变Mx 8将被隔离，以表征其基本功能，我们将尝试使用条件极性插入的新方法来确定两个非必需的噬菌体功能，并与它们的蛋白质产物的噬菌体基因。

The sequence of the G+C-rich temperate bacteriophage Mx8 genome shows that it is unlike any phage examined in detail to date. Our continuing studies of Mx8 genes and their functions will likely reveal new regulatory paradigms that are also used by its M. xanthus host during the process of multicellular development. We will try to uncover the secret of a unique phage-host adaptation: how is the Mx8 prophage maintained stably throughout M. xanthus multicellular development, despite the dramatic, successive, global changes in gene regulation that occur during this cycle? We will complete the sequence of the remaining third of the 50 kb Mx8 genome, to identify the Mx8 genes involved in lysogenic development, lytic development, and the stability of the Mx8 prophage throughout the multicellular developmental cycle of its host. The structure and function of a divergent pair of Mx8 promoters will be dissected, to learn what sequence elements are critical for strong promoter function in M. xanthus. A single-copy plasmid will be used to trap vegetative M. xanthus promoters, to expose their consensus sequence elements. Phage promoters will be cloned, to learn when they are activated during the lytic cycle of phage growth, or from an Mx8 prophage during the multicellular development of an M. xanthus lysogen. Mutations will be made in the genes controlling Mx8 superinfection immunity, to understand its novel dosage-dependent mechanism, in the repressor gene, to permit the inducible expression of genes from a strong Mx8 promoter and in the phage terminase, to construct high-frequency generalized transducing mutants. Temperature-sensitive mutations in Mx8 will be isolated to characterize its essential functions, and we will attempt to use conditionally-polar insertions in new ways to identify both nonessential phage functions, and to correlate phage genes with their protein products.