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Dissertation Information for Jennifer Kay Wagner

NAME:
- Jennifer Kay Wagner

DEGREE:
- Ph.D.

DISCIPLINE:
- Biology

SCHOOL:
- Indiana University (USA) (2005)

ADVISORS:
- Yves Brun

COMMITTEE MEMBERS:
- Elizabeth Raff
- Clay Fuqua
- Malcolm Winkler

MPACT Status: Incomplete - Not_Inspected

Title: Investigations into the structure and function of the Caulobacter crescentus stalk

Abstract: Bacterial stalks are extensions of the cell envelope. We investigated two aspects of the C. crescentus stalk: synthesis and function. To test our hypothesis that stalk synthesis is a specialized form of cell elongation, we examined the roles of two proteins important for cell elongation, RodA and MreB. In C. crescentus , the rodA gene is essential, and RodA depletion leads to a lass of control over stalk and cell body diameter, and a stalk elongation defect. We also demonstrate MreB depletion or inhibition leads to a stalk elongation defect. These results suggest that stalk synthesis is a more constrained form of cell elongation. We also show that cells recovering from MreB depletion exhibit a strong budding and branching cell body phenotype and possess ectopic poles, as evidenced by the presence of multiple, misplaced, and sometimes highly branched stalks at the ends of some of these buds and branches. This phenotype is also seen to a lesser extent in cells recovering from RodA depletion and mecillinam treatment. We conclude that MreB, RodA, and the targets) of mecillinam all contribute to the maintenance of cellular polarity in C. crescentus . We also investigated the function of the C. crescentus stalk. Stalks are hypothesized to act as antennae to take up nutrients from the environment. We addressed the nutrient uptake hypothesis using a variety of biochemical, proteomic, and cell biological methods. Our results indicate that the stalk is compartmentalized from the cell body and we present several models for how this compartmentalization is achieved. Stalks are capable of taking up and hydrolyzing an alkaline phosphatase substrate, but do not appear to contain PstA, an inner membrane component of the high affinity phosphate transport system. Stalks also do not contain one of C. crescentus ' two ExbB proteins, which are required components of the TonB-dependent transport system. Our results best support a nutrient uptake model for C. crescentus stalks in which nutrients are transported across the outer membrane by an unknown mechanism where they may then diffuse from the periplasm of the stalk to the periplasm of the cell body.

MPACT Scores for Jennifer Kay Wagner

A = 0
C = 0
A+C = 0
T = 0
G = 0
W = 0
TD = 0
TA = 0
calculated 2010-10-18 20:48:55

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