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Bacterial Adaptive Responses - Coping with Oxygen Limitation, Reactive Nitrogen Species and Disulfide Stress

Rogstam, Annika LU (2009)
Abstract
Bacteria have a remarkable ability to adapt to different environments. When bacteria encounter stress that causes macromolecular damage in the cell, leading to a suboptimal performance of cell metabolism, they can elicit an adaptive response. In this thesis Bacillus subtilis is used as the primary model organism to study bacterial adaptation to oxygen limitation, reactive nitrogen species and disulfide stress. Sudden changes in the oxygen availability leads to changes in the intracellular NAD:NADH ratio. In this work, the B. subtilis Rex protein is characterized. Rex acts as a transcriptional repressor that can sense the intracellular NADH concentration. When the concentration of NADH is low, Rex represses genes needed for growth under... (More)
Bacteria have a remarkable ability to adapt to different environments. When bacteria encounter stress that causes macromolecular damage in the cell, leading to a suboptimal performance of cell metabolism, they can elicit an adaptive response. In this thesis Bacillus subtilis is used as the primary model organism to study bacterial adaptation to oxygen limitation, reactive nitrogen species and disulfide stress. Sudden changes in the oxygen availability leads to changes in the intracellular NAD:NADH ratio. In this work, the B. subtilis Rex protein is characterized. Rex acts as a transcriptional repressor that can sense the intracellular NADH concentration. When the concentration of NADH is low, Rex represses genes needed for growth under conditions of low oxygen availability. Reactive nitrogen species (RNS) are present in many environments inhabited by bacteria, and may cause severe damage to bacterial cells. Here, we show that the major enzyme required for protection against RNS in B. subtilis is the Hmp flavohemoglobin. The hmp gene is regulated by the ResDE two-component system and the NsrR transcriptional repressor. Under normal conditions, the bacterial cell cytoplasm is a reducing environment where protein cysteines are kept in their reduced form. However, if the cytoplasm becomes oxidizing, unwanted disulfide bonds may form, a phenomenon known as disulfide stress. Spx is a global regulator governing the disulfide stress response in B. subtilis. Under non-stress conditions, Spx is rapidly degraded by the ClpXP protease. In this work, YjbH is identified as a negative effector of Spx, that is required for the efficient degradation of Spx by ClpXP. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Paget, Mark, Department of Biochemistry, School of Life Sciences, University of Sussex, Falmer, Brighton, UK
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Bacillus subtilis, redox regulation, nitrosative stress, disulfide stress
pages
148 pages
defense location
Biology Lecture Hall, Sölvegatan 35, Lund
defense date
2009-05-28 09:30
ISBN
978-91-85067-54-1
language
English
LU publication?
yes
id
0e42dc0d-155a-4814-bf6b-70fca63d285f (old id 1391717)
date added to LUP
2009-05-04 10:56:05
date last changed
2016-09-19 08:45:17
@misc{0e42dc0d-155a-4814-bf6b-70fca63d285f,
  abstract     = {Bacteria have a remarkable ability to adapt to different environments. When bacteria encounter stress that causes macromolecular damage in the cell, leading to a suboptimal performance of cell metabolism, they can elicit an adaptive response. In this thesis Bacillus subtilis is used as the primary model organism to study bacterial adaptation to oxygen limitation, reactive nitrogen species and disulfide stress. Sudden changes in the oxygen availability leads to changes in the intracellular NAD:NADH ratio. In this work, the B. subtilis Rex protein is characterized. Rex acts as a transcriptional repressor that can sense the intracellular NADH concentration. When the concentration of NADH is low, Rex represses genes needed for growth under conditions of low oxygen availability. Reactive nitrogen species (RNS) are present in many environments inhabited by bacteria, and may cause severe damage to bacterial cells. Here, we show that the major enzyme required for protection against RNS in B. subtilis is the Hmp flavohemoglobin. The hmp gene is regulated by the ResDE two-component system and the NsrR transcriptional repressor. Under normal conditions, the bacterial cell cytoplasm is a reducing environment where protein cysteines are kept in their reduced form. However, if the cytoplasm becomes oxidizing, unwanted disulfide bonds may form, a phenomenon known as disulfide stress. Spx is a global regulator governing the disulfide stress response in B. subtilis. Under non-stress conditions, Spx is rapidly degraded by the ClpXP protease. In this work, YjbH is identified as a negative effector of Spx, that is required for the efficient degradation of Spx by ClpXP.},
  author       = {Rogstam, Annika},
  isbn         = {978-91-85067-54-1},
  keyword      = {Bacillus subtilis,redox regulation,nitrosative stress,disulfide stress},
  language     = {eng},
  pages        = {148},
  title        = {Bacterial Adaptive Responses - Coping with Oxygen Limitation, Reactive Nitrogen Species and Disulfide Stress},
  year         = {2009},
}