Joint Research on Myxobacterial Development

粘细菌是一种独特的革兰氏阴性细菌，它经历多细胞发育。当营养物质在固体培养基中耗尽时，细胞聚集形成丘，最终转化为子实体。杆状细胞分化为圆形或卵圆形孢子。在黄色粘球菌的发育过程中，已知发生五个细胞间信号交换循环。的fruA基因编码一个假定的25 kDa的转录因子，黄曲霉的发展必不可少的。在本研究中，我们已经证明了存在一个假定的阻遏物X的fruA表达的凝胶迁移实验。结合竞争实验表明X识别序列。通过质谱分析蛋白质P15的结构，蛋白质P15的表达被fruA突变抑制。在ORF134中插入卡那霉素抗性DNA片段导致发育失败，这表明ORF134-fruB操纵子的存在负责黄曲霉的发育。两个启动子结构被发现这个操纵子：一个启动子在营养生长过程中工作，而两个启动子在发育过程中工作。发现M.xanthus lonD是一个热激基因。lonD的表达不依赖于编码大肠杆菌RpoH同源物的sigBCE基因，但依赖于编码RpoD同源物的hsfA和sigA。hsfA基因编码一个假定的效应的双组分系统，这是磷酸化的HsfB激酶。磷酸化的HsfA与lonD基因的启动子序列结合。黄色分枝杆菌携带至少13种真核样蛋白Ser/Thr pkn激酶。通过双杂交实验发现许多基因产物与Pkn激酶相互作用。

Myxobacteria are unique gram-negative bacteria which undergo multicellular development. When nutrients are depleted in a solid medium, cells aggregate to form mounds which eventually convert to fruiting bodies. Rod-shaped cells differentiate to round or ovoid spores. During the development of Myxococcus xanthus, five cycles of intercellular signal exchanges are known to occur. The fruA gene encodes a putative 25-kDa transcription factor essential for the development of M.xanthus. In the present study, we have demonstrated the presence of a putative repressor X for fruA expression by gel shift experiments. Binding competition experiments suggested the X recognition sequence. Structure of protein P15, expression of which was inhibited by the fruA mutation, was analyzed by mass spectroscopy. Insertion of kanamycin-resistance DNA fragment into ORF134 resulted in failure of development, suggesting the presence of ORF134-fruB operon responsible for M.xanthus development. Two promoter structures were found for this operon : One promoter works during vegetative growth, while both two promoters work during development. M.xanthus lonD was found to be a heat shock gene. Expression of lonD was independent on sigBCE genes encoding an Escherichia coli RpoH homolog, but dependent on hsfA and sigA encoding a RpoD homolog. The hsfA gene encodes a putative effecter of a two-component system, which was phosphorylated by HsfB kinase. Phosphorylated-HsfA bound to promoter sequence for lonD gene. M.xanthus carries at least 13 eukaryotic-like protein Ser/Thr pkn kinases. Many gene products were found to interact with Pkn kinases by two-hybrid experiments.