DNA segregation during Bacillus growth and development

描述（由申请人提供）：本提案的目标是确定芽孢杆菌物种中大，低拷贝数质粒的DNA分离机制。通过对苏云金芽孢杆菌质粒pBtoxis的研究，我们发现了一种属于微管蛋白超家族的新型分离蛋白。TubZ是一种分散的微管蛋白样蛋白，它组装了质粒pBtoxis稳定遗传所必需的动态聚合物。微管蛋白样蛋白通常在芽孢杆菌毒力质粒上发现，但它们如何促进质粒的稳定性尚不清楚。我们还鉴定了几个家族的不同的肌动蛋白样蛋白参与质粒DNA分离枯草芽孢杆菌。质粒pLS32的AlfA和Alp7A都可以组装聚合物，但它们似乎通过不同的机制分离质粒。本研究的目的是了解芽孢杆菌微管蛋白和肌动蛋白在质粒DNA分离中的生化特性、体内组装动力学和功能。由于芽孢杆菌致病性菌株（如炭疽芽孢杆菌的pXO1）的质粒上编码了多种毒力因子，因此了解质粒如何从一代传递到下一代对于理解这些关键毒力决定因素的进化和传播非常重要。

DESCRIPTION (provided by applicant): The goal of this proposal is to identify the mechanisms of DNA segregation for large, low copy number plasmids in Bacillus species. From studying plasmid pBtoxis in Bacillus thuringiensis, we identified a novel segregation protein belonging to the tubulin superfamily. TubZ is a divergent tubulin like protein that assembles dynamic polymers essential for the stable inheritance of plasmid pBtoxis. Tubulin-like proteins are commonly found on Bacillus virulence plasmids, but how they contribute to plasmid stability is unknown. We have also identified several families of divergent actin-like proteins involved in plasmid DNA segregation in Bacillus subtilis. AlfA of plasmid pLS32 and Alp7A both assemble polymers, but they appear to segregate plasmids by different mechanisms. The goal of this proposal is to understand the biochemical properties, in vivo assembly dynamics, and the functions of Bacillus tubulins and actins involved in plasmid DNA segregation. Since a wide variety of virulence factors are encoded on plasmids in pathogenic strains of Bacillus, such as pXO1 of B. anthracis, understanding how plasmids are transmitted from one generation to the next is important for understanding the evolution and spread of these key virulence determinants. PUBLIC HEALTH RELEVANCE: This study focuses on understanding how bacterial plasmids are inherited. Plasmids play key roles in bacterial pathogenesis, as they are often transmissible and encode antibiotic resistance and virulence traits, such as toxins and capsules. These studies could therefore help identify targets for new narrow spectrum antibiotics, since blocking plasmid stability will in certain infections decrease pathogenicity.