GENE EXPRESSION DURING SPORULATION

芽孢杆菌和梭状芽孢杆菌形成孢子是一种原始的细胞分化系统。它涉及到一个位置不对称的分割。这就产生了两种不同的细胞类型，母细胞和前孢子，它们有着完全不同的发育命运。前孢子被母细胞吞没，发育成成熟的、耐热的孢子。母细胞是发育所必需的，但最终会溶解。在枯草芽孢杆菌中，已经证明两种RNA聚合酶sigma因子F和E在分裂时被激活，其中sigmaF只在孢子前活性，而sigmaE只在母细胞中活性。这些sigma因子指导后续的区隔化基因表达程序，但不指导区隔化过程。正在解决的主要问题是基因表达的区隔化是如何建立的，以及基因表达如何与形态变化协调。关于芽孢杆菌和梭状芽孢杆菌的区隔化的一个主要特征是孢子分裂的位置非常不对称。这是提议测试的其他可能的决定因素，区隔在一种孢子形成的球菌，孢芽孢杆菌脲，其中孢子分裂是对称定位。提出了一个两部分的系统来测试划分的完整性。该系统将用于搜索和表征枯草芽孢杆菌突变与受损区隔。它也将被用来测试葡萄球菌区隔的完整性。我们建议探究枯草芽孢杆菌不对称分裂对SpoIIE蛋白的要求。提出了染色体分解在孢子形成中的作用。提出鉴定和表征参与芽孢杆菌母细胞吞噬前孢子的基因。

Formation of spores by species of Bacillus and Clostridium is a primitive system of cell differentiation. It involves an asymmetrically located division. This gives rise to two distinct cell types, the mother cell and the prespore, which have radically different developmental fates. The prespore is engulfed by the mother cell and develops into the mature, heat- resistant spore. The mother cell is required for that development but ultimately lyses. In Bacillus subtilis it has been shown that two RNA polymerase sigma factors, F and E, are activated upon division, with sigmaF active exclusively in the prespore and sigmaE active exclusively in the mother cell. These sigma factors direct the subsequent program of compartmentalized gene expression, but do not direct the process of compartmentalization. The main problems being addressed are how compartmentalization of gene expression is established and how gene expression is coordinated with morphological changes. A dominant feature in the thinking about compartmentalization in Bacilli and Clostridia has been the grossly asymmetric location of the sporulation division. It is proposed to test for other possible determinants of compartmentalization in a species of spore-forming coccus, Sporosarcina ureae, in which the sporulation division is symmetrically located. It is proposed to develop a two-part system that tests the completeness of compartmentalization. This system will be used to search for and characterize B. subtilis mutants with impaired compartmentalization. It will also be used to test the completeness of compartmentalization in S. ureae. It is proposed to explore the requirement for the SpoIIE protein in order to have an asymmetric division in B. subtilis. It is proposed to test the role of chromosome resolution in spore formation. It is proposed to identify and characterize genes involved in engulfment of the prespore by the mother cell in B. subtilis.