Dynamic Characterization of a Model Signal Transduction System

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Intellectual meritThe goal of this research is to further our understanding of how cells respond to environmental signals and stresses and specifically to quantitatively investigate and model phenotypic variations in this response. Towards this goal, this project will critically examine the dynamics of the response of the model organism Escherichia coli (E. coli) to environmental stress in the form of nutrient limitation (specifically, inorganic phosphate). Under these conditions, the PhoR/PhoB two-component system signaling pathway is activated with the ultimate response being the activation of gene transcription of the proteins of the PhoR/PhoB two-component system in an attempt by the cell to scavenge the dwindling supply of nutrient. The response to changes in environmental phosphate will be monitored through direct imaging of the production rate of a fluorescent protein biomarker placed in the E. coli genome under control of the PhoR/PhoB two-component system. Quantification of the protein production rate and its variance among a population of cells will be performed using epi-fluorescence video microscopy with single fluorescent protein sensitivity. Beyond measurement of the response, this project will also develop simplified models of the two-component system which are mathematically tractable and use Stochastic Simulation and Finite State Projection methods to predict both the mean and variance of the response in these models. Predictions from models can be tested experimentally and guide new experimental directions while experimental results may necessitate modifications of the simplified models. Through this, the project will obtain new quantitative insight into the mechanism of phenotypic variation in the cellular response to environmental signals/stresses. Broader ImpactsThis project affords opportunities for undergraduate and graduate students and postdoctoral trainees, classically educated in the life or physical sciences, to conduct multidisciplinary research at the interface of physics and biology. The principal investigators are involved in undergraduate education in research both through their institutions and through participation in REU and MARC programs. A primary goal of this project is to train multidisciplinary scientists at all levels. The students and post-doctoral trainees will be encouraged to attend and present their research at major national and international meetings to expose them to the breadth of research being performed in the life and physical sciences which will translate into novel ideas and approaches in their own work. General lectures will be periodically given to local high school classes to pique the interest of tomorrow's scientists in multidisciplinary research. Further, both principal investigators are committed to improving diversity and gender equality in the life and physical sciences.