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Penicillin-binding protein 2 is essential in wild-type Escherichia coli but not in lov or cya mutants
1Department of Molecular Genetics, Kumamoto University Medical School, Japan.
Abstract:
Penicillin-binding protein 2 (PBP2), target of the beta-lactam mecillinam, is required for rod morphology and cell wall elongation in Escherichia coli. A new temperature-sensitive PBP2 allele and an in vitro-constructed insertion deletion allele were shown to be lethal in wild-type strains, establishing that the activity of this protein is essential. Mutations in the lov or cya genes, conferring mecillinam resistance, compensated for the deleterious effect of the absence of PBP2. The resulting double mutants grew as spheres. In a cya mutant lacking PBP2, the restoration of a Cya+ phenotype by addition of cyclic AMP caused lethality and a block in cell division. These results show that in wild-type cells, PBP2 is essential for growth and division.
Insights
Penicillin-binding protein 2 (PBP2) is essential for Escherichia coli growth and cell division. Its absence causes lethality, but mecillinam resistance mutations can restore viability, leading to spherical cell morphology.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Cell Division
Background:
- Penicillin-binding protein 2 (PBP2) plays a crucial role in maintaining rod morphology and facilitating cell wall elongation in Escherichia coli.
- PBP2 is the molecular target of the beta-lactam antibiotic mecillinam.
Purpose of the Study:
- To establish the essentiality of PBP2 activity for Escherichia coli viability.
- To investigate the relationship between PBP2 function, mecillinam resistance, and cell morphology.
- To elucidate the role of PBP2 in cell division.
Main Methods:
- Construction and characterization of temperature-sensitive and insertion-deletion PBP2 alleles.
- Generation of double mutants by combining PBP2 alleles with mecillinam resistance mutations (lov or cya).
- Phenotypic analysis of wild-type and mutant strains, including cell morphology and growth characteristics.
- Investigation of cyclic AMP (cAMP) effects on a PBP2-deficient cya mutant.
Main Results:
- Both temperature-sensitive and insertion-deletion PBP2 alleles were lethal in wild-type Escherichia coli, confirming PBP2's essential function.
- Mutations conferring mecillinam resistance (in lov or cya genes) rescued the lethality associated with PBP2 absence, resulting in spherical cell growth.
- Restoration of a Cya+ phenotype in a PBP2-deficient cya mutant using cyclic AMP addition led to lethality and blocked cell division.
Conclusions:
- PBP2 activity is indispensable for the growth and division of Escherichia coli.
- The study highlights a complex interplay between PBP2, mecillinam resistance mechanisms, and cell division processes.
- Disruption of PBP2 function has profound effects on cell morphology and viability.