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Murein segregation in Escherichia coli
M A de Pedro1, J C Quintela, J V Höltje
1Centro de Biología Molecular Severo Ochoa Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Facultad de Ciencias, Spain. madepedro@mvax.cbm.uam.es
Abstract:
Peptidoglycan (murein) segregation has been studied by means of a new labeling method. The method relies on the ability of Escherichia coli cells to incorporate D-Cys into macromolecular murein. The incorporation depends on a periplasmic amino acid exchange reaction. At low concentrations, D-Cys is innocuous to the cell. The distribution of modified murein in purified sacculi can be traced and visualized by immunodetection of the -SH groups by fluorescence and electron microscopy techniques. Analysis of murein segregation in wild-type and cell division mutant strains revealed that murein in polar caps is metabolically inert and is segregated in a conservative fashion. Elongation of the sacculus apparently occurs by diffuse insertion of precursors over the cylindrical part of the cell surface. At the initiation of cell division, there is a FtsZ-dependent localized activation of murein synthesis at the potential division sites. Penicillin-binding protein 3 and the products of the division genes ftsA and ftsQ are dispensable for the activation of division sites. As a consequence, under restrictive conditions ftsA,ftsI,or ftsQ mutants generate filamentous sacculi with rings of all-new murein at the positions where septa would otherwise develop.
Insights
A novel D-Cys labeling method visualizes peptidoglycan (murein) segregation in Escherichia coli. Murein in polar caps is inert and conserved, while cell division involves localized synthesis activation.
Area of Science:
- Microbiology
- Cell Biology
- Biochemistry
Background:
- Peptidoglycan (murein) is essential for bacterial cell shape and integrity.
- Understanding murein segregation is crucial for comprehending bacterial cell division.
- Existing methods for studying murein dynamics have limitations.
Purpose of the Study:
- To develop and apply a new method for visualizing and analyzing peptidoglycan segregation in Escherichia coli.
- To investigate the dynamics of murein distribution during cell growth and division.
- To identify key factors and mechanisms involved in murein segregation.
Main Methods:
- Development of a D-Cysteine (D-Cys) labeling technique for incorporating into bacterial murein.
- Utilizing immunodetection of incorporated D-Cys via fluorescence and electron microscopy.
- Analyzing murein segregation patterns in wild-type and cell division mutant strains of E. coli.
Main Results:
- Polar cap murein is metabolically inert and segregated conservatively.
- Cellular sacculus elongation occurs through diffuse insertion of new murein precursors.
- FtsZ-dependent localized murein synthesis is activated at division sites.
- Certain division genes (ftsA, ftsI, ftsQ) and penicillin-binding protein 3 are not essential for this activation.
Conclusions:
- The D-Cys labeling method provides new insights into bacterial murein dynamics.
- Murein segregation follows distinct patterns during elongation and division.
- Localized murein synthesis activation is a key event in initiating cell division.
- The study clarifies the roles of specific genes in the cell division process.