The ability to maintain pH stability is critical for all living cells since proteins maintain their natural structure and function only within a narrow and optimal pH range. This ability is especially critical for single-celled bacteria that experience a far larger range of stress conditions compared to a typical cell from a more complex organism. Bacteria largely rely on membrane transport proteins to counter rapid changes in environmental pH. However, little is known about how cell morphology is modulated under stress conditions to support the transport function. The genetically tractable E. coli will be used as a model system to develop a molecular understanding of how bacterial membrane integrity, cell shape, and transport processes are integrated, and the overall impact these processes have on bacterial survival during environmental fluxes. To generate interest and excitement in fundamental aspects of microbial biology relevant to our understanding of physiology, ecology, medicine, and industry, early-stage undergraduates will be incorporated into several aspects of the project both in the classroom and in the research laboratory. Many of these students are likely to belong to communities currently underrepresented in the STEM disciplines.
In order to counteract pH stress, bacteria utilize multiple strategies, chief among which is the expression and activation of cytoplasmic membrane-spanning proton transporters, which play essential roles in the maintenance of proton motive force across the cytoplasmic membrane and aid in pH homeostasis. An auxiliary property of a class of these transporters is their ability to pump out numerous unrelated drugs and provide resistance to biocides. Often, pH stresses overlap with salt and cell envelope stresses due to the increase in sodium cytotoxicity at high pH, and the susceptibility of certain cell wall biosynthetic enzymes to altered pH. While much is known about individual strategies of pH responses in bacteria, the integration and overlap of these responses with salt stress and cell envelope integrity, is poorly understood. To address this gap, this research will identify as yet uncharacterized cellular factors involved in the interplay between stress responses and morphogenesis. The repertoire of powerful genetic tools in E. coli in combination with molecular, cell biological, biochemical experiments, and microscopy techniques, will be exploited to define the specific function of each protein, and determine how they interact with known cell morphology factors. These studies are expected to enhance our understanding of how bacterial cell morphology and membrane integrity are maintained in response to multiple stresses.
