In recent years, a number of studies have revealed that the ability of bacteria to communicate with each other is far more widespread than previously realized. This cell-to-cell communication is mediated by a variety of "languages" or chemical signals. The ability to communicate is a fundamental requirement for a number of bacterial processes including: (i) the differentiation of cells to form spores, (ii) the formation of complex microbial communities termed biofilms, and (iii) the ability to express virulence genes required for bacterial pathogenicity. Previous studies, funded by the NSF, resulted in the identification of a novel mechanism for cell-to-cell signaling in bacteria. This mechanism requires a new family of proteins, termed rhomboid, that are found in prokaryotes and eukaryotes. The rhomboid proteins are proteases and cleave a second protein to release a fragment that ultimately becomes a peptide-like signaling molecule. Two bacterial rhomboids, AarA from Providencia stuartii and GlpG from E. coli will be studied in this proposal. The mechanisms by which they generate an extracellular signal will be addressed using genetic and biochemical techniques. Structural studies using mass spectrometry will be used determine the chemical nature of the extracellular signal. This project will also investigate the genes in E. coli that are regulated by this signaling pathway to determine its role in cell physiology.
The broader significance of this project is two-fold. First, the rhomboid-mediated pathway appears to be widespread in bacteria. This project will provide a framework for understanding the function and regulation of these signaling pathways in other bacteria. Moreover, the analysis of bacterial rhomboid proteins may reveal new insights into the function of these proteins in higher organisms, including humans. This has important implications for understanding developmental signaling pathways. Second, this project will provide important training opportunities for undergraduate and graduate students, as well as postdoctoral fellows.
