Dynamic Subcellular Protein Localization During Bacillus Subtilis Sporulation

University Of California-San Diego, La Jolla CA

Investigators

Abstract

The localization of membrane proteins to specific regions of the cell is a conserved and essential feature of both prokaryotic and eukaryotic cells. In bacteria, protein localization is essential for cell division, DNA replication, as well as for chemotaxis, pathogenesis and the development of specialized cell types. However, in contrast to eukaryotic cells, little is known about the mechanism by which proteins reach their correct subcellular location in bacterial cells. Many cases of protein localization in bacteria involve the localization of membrane proteins to specific regions of the cytoplasmic membrane, often at the cell pole or septum. During B. subtilis sporulation, protein localization involves the specific localization of proteins to one of two separate membranes within the cell, similar to eukaryotic protein localization. The long term goals of the research described here are to understand the mechanism by which bacterial membrane proteins assemble at their correct locations within the cell. This project uses genetic and cell biological methods to investigate the mechanism by which proteins localize to specific membrane regions during sporulation, and to investigate the possibility that B. subtilis contains two integral membrane protein insertion complexes that serve to direct membrane proteins to different locations within the cell. It will also develop new methods to investigate if proteins made before division are restricted to one or the other cell after division, or if they are differently localized in the two cells, as these processes may provide a simple mechanism to generate daughter cells of differing fate. They also may control the activity of proteins that act in a vectoral manner across a newly-synthesized septum. These studies will provide further insight into the mechanism by which integral membrane proteins reach their correct subcellular address in bacterial cells. Thus far, the mechanisms of integral membrane protein insertion and assembly have been almost exclusively studied in Gram negative bacteria, primarily in E. coli. These studies will be extended to the Gram positive bacterium B. subtilis, which represents a separate bacterial kingdom that includes many human pathogens such as the Mycobacteria, Streptococcus sp. and Staphylococcus sp., and many bacteria of industrial importance, such as the Actinomycetes. The project will contribute to training graduate and undergraduate students in microbial cell biology and genetics.