The role of cysteine and the Cpx envelope stress response in alleviating zinc induced stress in Escherichia coli

• Author / Creator

  Zimba, Joseph

• Circumscribing the interior of Gram negative bacteria are two sets of layers: an inner and outer membrane. The periplasm and murein occupy the space between these membranes and acts as a site for protein folding and degradation. The bacterial envelope, as a whole, plays an essential role in the survival of the cell – providing structural support and as well carrying out cellular functions that are vital for the cell. Maintaining the envelope homeostasis is crucial for the cell’s survival. Gram negative bacteria, such as Escherichia coli, employ envelope stress response systems, including the Cpx Two Component Signal Transduction System, that play a regulatory role of monitoring changes in the bacterial cell envelope and maintaining its integrity. The Cpx pathway is primarily induced by stress signals that affect the cell envelope such as alkaline pH, overexpression of specific membrane associated proteins, perturbations in membrane structure, and adhesion to abiotic surfaces. In response, the Cpx response regulates the expression of a number of genes involved in protein folding and degradation. Previous studies have demonstrated that the Cpx response is activated in the presence of excess external zinc, though the mechanism of activation and the direct effect that zinc has on E. coli is not fully understood. The objective of this thesis was to elucidate the mechanism that the Cpx response uses to sense external zinc and the role that the Cpx response has in mediating adaptation to zinc toxicity. Using luminescence and qPCR we provide results to show that the Cpx response senses the toxic effects of zinc in a CpxA dependent manner suggesting that zinc has an extracytoplasmic effect on E. coli. We also demonstrate that zinc has an effect on membrane permeability and provide evidence which suggests that the Cpx response could be sensing redox changes in the periplasm brought about by excess zinc such as the accumulation of cysteine, which is upregulated in response to excess zinc.

• Subjects / Keywords

  • Escherichia coli
  • cysteine
  • Envelope stress
  • zinc
  • Cpx

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3VH5D08H

• License

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