Biogenesis of Bordetella cell envelope components

革兰氏阴性菌的包膜很复杂。它由细胞膜和细胞壁组成。细胞壁由一层薄薄的肽聚糖结构组成，周围是一层不对称的外膜双分子层，由磷脂和脂多糖组成，其中附着或嵌入各种（脂）蛋白。内膜和外膜之间的空间称为外周质。除了作为一种选择性屏障和保护细菌免受恶劣条件的影响外，包膜在决定细菌与其环境之间相互作用的结果方面起着关键作用。事实上，细胞包膜的几个组成部分受到环境条件的调节。此外，包膜组分的生物发生也很复杂；将包膜成分定位到特定位置需要专用的分子机械和机制来维持成分处于适合于能够穿过一个或多个膜的状态。这些机制也可以帮助促进组件到达目的地后的功能。

The envelope of Gram negative bacteria is complex. It comprises the inner membrane and the cell wall. The cell wall consists of a thin peptidoglycan structure surrounded by an asymmetric outer membrane bilayer consisting of phospholipids and lipopolysaccharides within which are attached or embedded various (lipo)proteins. The space between the inner and outer membranes is called the periplasm. In addition to functioning as a selective barrier and protecting bacteria from harsh conditions, the envelope plays a critical role in determining the outcome of interactions between the bacterium and its environment. Indeed, several components of the cell envelope are regulated in response to environmental conditions. Furthermore, the biogenesis of envelope components is also complex; targeting envelope components to specific locations requires dedicated molecular machinery and mechanisms that maintain the components in a state suited to being able to traverse one or more membranes. These mechanisms may also assist in promoting the function of the components once they have reached their destination. This proposal addresses components comprising the envelope of Bordetella species. Many Bordetella species are human or animal pathogens and there is much to learn about how the Bordetella envelope is made. We will focus on two aspects of the Bordetella envelope the biogenesis of surface proteins called autotransporters and a system that modifies the lipid A portion of lipopolysaccharide. We will characterize how two novel autotransporters with distinct and non-typical structures are secreted past the outer membrane. We will ascertain the requirement for accessory factors, how these autotransporter proteins interact with accessory factors, the role of the autotransporter C-terminus in effecting secretion, and how the proteins fold on the bacterial surface following secretion. With respect to lipid A modification, we will characterize the mechanism of how a group of proteins function together to modify lipid A with glucosamine at the inner membrane of the cell envelope. This process is highly regulated and is predicted to involve several regulatory systems, including a putative anti-sense RNA. We will investigate how this system is coordinated. Understanding how the envelope is built, especially in non model organisms can lead to uncovering fundamental principles of how membranes and membrane proteins and lipids are made and can also lead to improved methods for cell surface display or manipulation that can be used in bio and nanotechnology applications.