GENETICS OF MYXOPHAGES

富含G+ c的温带噬菌体Mx8基因组序列表明，它不同于迄今为止详细检查的任何噬菌体。我们对Mx8基因及其功能的进一步研究可能会揭示其多细胞发育过程中Mx8宿主所使用的新的调控模式。我们将试图揭示一种独特的噬菌体-宿主适应的秘密：尽管在这个周期中发生了巨大的、连续的、全球性的基因调控变化，但Mx8噬菌体是如何在整个M. xanthus多细胞发育过程中保持稳定的？我们将完成50 kb Mx8基因组剩余三分之一的序列，以鉴定在宿主多细胞发育周期中参与溶原发育、裂解发育和Mx8前噬菌体稳定性的Mx8基因。我们将剖析Mx8启动子对的结构和功能，以了解哪些序列元素对黄豆属植物的强启动子功能至关重要。单拷贝质粒将用于诱捕无性黄豆芽胞杆菌启动子，以暴露其一致的序列元素。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. xanthus溶原的多细胞发育过程中何时被Mx8噬菌体激活。将在控制Mx8重复感染免疫的基因中进行突变，以了解其新的剂量依赖机制，在抑制基因中进行突变，以允许来自强Mx8启动子的基因的诱导表达，并在噬菌体端酶中进行突变，以构建高频广义转导突变体。Mx8的温度敏感突变将被分离以表征其基本功能，我们将尝试以新的方式使用条件极性插入来鉴定非必需噬菌体功能，并将噬菌体基因与其蛋白质产物相关联。

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.