Control of cell envelope integrity and DNA supercoiling by cytoplasmic Mg2+: revealing novel principles to manipulate bacteria
Abstract
Cell integrity is essential to all living organisms. How cells maintain integrity when faced with specific stressors holds promise for engineering organisms that withstand extreme environments and for identifying strategies to permeabilize and destroy cells. We hypothesize that many diverse bacterial species change their membranes and other cell envelope components in response to a decrease in the cytosolic magnesium (Mg2+) concentration and that these changes are coordinated with their global DNA supercoiling status, thereby altering bacterial physiology in multiple ways. Mg2+ is the most abundant divalent cation in all living cells, playing essential roles in a variety of biochemical reactions, the assembly and functioning of ribosomes, and the neutralization of negative charges of polyphosphate in the cytoplasm, and of phospholipid headgroups in the inner and outer membranes and of lipopolysaccharide phosphates in Gram-negative bacteria. We propose to reveal how cellular Mg2+ controls cell envelope integrity and DNA supercoiling in the model pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium), exploiting the fact that Mg2+ homeostasis is best understood in this bacterium. The response to low Mg2+ is governed by the widely distributed regulatory system PhoP/PhoQ. The sensor PhoQ responds to low Mg2+ in the periplasm by promoting the phosphorylated (active) form of PhoP, a DNA binding protein that controls transcription of hundreds of genes Ð including those mediating resistance to noxious compounds and modification of the bacterial cell envelope. Our research will: (I) Identify cell envelope changes promoted in low cytoplasmic Mg2+, thereby revealing PhoP-dependent and - independent changes in cell envelope composition and stability and establishing how these changes impact bacterial susceptibility to various antimicrobial agents. The resulting findings will provide new means to manipulate cell envelope integrity and stability. (II) Establish how cytoplasmic Mg2+ controls global DNA supercoiling, thereby defining the mechanisms by which a continuous decrease in cytoplasmic Mg2+ determines DNA supercoiling, an essential property of all living cells. The expected results will be widely applicable given the universality of Mg2+ and DNA supercoiling. And (III) Determine mechanisms by which Mg2+ changes the cell envelope and DNA supercoiling, thereby establishing the connection between changes in the cell envelope and global DNA supercoiling triggered in low cytoplasmic Mg2+. This aim will uncover novel concepts about communication between subcellular compartments likely applicable across species. Achievement of these specific aims will define the strategies cells adopt to cope with low cytoplasmic Mg2+ both inside and outside host cells and establish mechanisms by which cell growth can be newly manipulated.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 19, 2023
- Source ID
- W911NF2310139
Entities
People
- Eduardo Groisman
Organizations
- Army Contracting Command
- United States Army
- Yale University