Incompatibility exhibited by colicin plasmids E1, E2, and E3 in Escherichia coli.

Area of Science:

• Microbiology
• Bacteriology
• Molecular Biology

Background:

• Colicins are bacteriocins produced by Escherichia coli.
• Colicin plasmids (Col E1, E2, E3) confer colicin production and immunity.
• Understanding plasmid interactions is crucial for bacterial genetics.

Purpose of the Study:

• To construct multiply colicinogenic Escherichia coli strains.
• To investigate plasmid compatibility and stability in multiply colicinogenic strains.
• To assess the impact of colicinogenicity on plasmid acquisition.

Main Methods:

• Construction of multiply colicinogenic E. coli using DNA transformation and bacterial conjugation.
• Phenotypic analysis of colicin production and immunity.
• Monitoring plasmid loss rates in doubly and triply colicinogenic cells.
• Assessing the acquisition of a conjugationally transferred Col E1 plasmid.

Main Results:

• Multiply colicinogenic strains produced colicins and exhibited immunity to all carried colicins.
• Observed plasmid incompatibility, with differential loss rates (Col E2 > Col E3 in doubly, Col E3 most stable in triply colicinogenic cells).
• Significantly reduced acquisition of a conjugationally transferred Col E1 plasmid by cells already carrying Col E1.

Conclusions:

• Multiply colicinogenic E. coli strains can be stably constructed.
• Plasmid incompatibility influences stability, with varying loss frequencies among Col E plasmids.
• Existing colicinogenicity confers a barrier to the acquisition of homologous plasmids.