Escherichia coli K317, formerly used to define colicin group E2, produces colicin E7, is immune to colicin E2, and carries a bacteriophage-restricting conjugative plasmid

Area of Science:

• Microbiology
• Bacteriology
• Genetics

Background:

• Colicins are bacteriocins produced by Escherichia coli that inhibit or kill related strains.
• Colicinogeny involves the production of colicins and immunity to them, often mediated by plasmids.
• Previous studies have characterized various colicin types and their genetic determinants.

Purpose of the Study:

• To characterize a novel colicin, designated E7, produced by Escherichia coli strain CL137.
• To investigate the genetic basis of colicin E7 production, immunity, and phage restriction.
• To identify and describe the plasmids responsible for these traits.

Main Methods:

• Bacterial conjugation experiments were used to transfer colicinogeny and immunity traits.
• Phenotypic characterization of Escherichia coli strains for colicin production, immunity, and phage sensitivity.
• Plasmid analysis to identify genetic elements responsible for observed traits.

Main Results:

• Escherichia coli strain CL137 produces a novel colicin, E7, and is immune to colicin E2.
• Conjugation experiments revealed the transfer of E7 colicinogeny and E2 immunity from strain K317.
• A plasmid, ColE2imm-K317, was identified as responsible for E2 immunity, and pRES-K317 for Tra+ and phage restriction.

Conclusions:

• A new colicin, E7, has been identified and characterized in Escherichia coli.
• Colicin E7 production and E2 immunity are plasmid-mediated traits.
• The plasmid pRES-K317 is associated with conjugational transfer and phage restriction capabilities.