Nutrient Uptake by the Stalk of Caulobacter crescentus

Trustees Of Indiana University, Bloomington IN

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Abstract

DESCRIPTION (provided by applicant): The long-term goal of this research is to determine why bacteria undergo specific changes in morphology. Bacteria, including pathogens, are found in a vast array of morphologies;however functions have rarely been attributed to specific shapes. In this work, the function of morphological changes in bacteria with cell membrane extensions, known as stalks, will examined as a model system to study the function of morphological adaptation. Recent mathematical models suggest that in nutrient limited environments, such as those inhabited by the stalked bacteria, increasing the length of the cell (and not the surface area) is the most important factor in increasing the efficiency of nutrient uptake. This suggests that the stalk plays a predominant role in the uptake of nutrients and promotes cell growth. Indeed, phosphate limitation is known to induce elongation of the stalk of Caulobacter crescents. In this work the contribution of stalks to nutrient uptake will be studied using two Gram negative bacteria, C. crescentus and Asticcacaulis biprosthecum. The comparative analysis between the mechanisms of nutrient uptake in these two bacterial species will help determine if the stalks arose by common descent or independently as consequence of living in similar nutrient-depleted environments. In this proposal, a multi-disciplinary approach is utilized to determine how nutrients are taken up by the stalk and transported to the cell body to be metabolized. Approaches used in this study will include fluorescence microscopy, microfluidics, proteomics, physiology, and mathematical modeling. The specific aims of this proposal are to: 1). determine the rates of diffusion of nutrients from the stalk to the cell body, 2). determine the mechanism and capacity of nutrient uptake by stalks, and 3). determine the complement of stalk proteins. The results of the experiments outlined in this proposal will provide valuable information about the stalk, a morphological adaptation, which likely allows the stalked bacteria to persist in nutrient-limited environments. Cell shape changes in response to environmental cues are well documented in a number of bacterial systems, including pathogens. Enhancing our understanding of how bacterial cell shapes are maintained, function, and change will provide valuable information about the ability of bacteria to persist in unfavorable environments. This information can be used to design strategies to impede the persistence and proliferation of bacteria in specific environments.