Characterization of E-type colicinogenic plasmids from Shigella sonnei

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Colicinogenic plasmids confer toxicity against related bacteria.
• Shigella sonnei is a significant human pathogen.
• Understanding plasmid diversity is crucial for tracking bacterial evolution.

Purpose of the Study:

• To molecularly characterize colicinogenic plasmids from Shigella sonnei clinical isolates.
• To investigate the genetic relatedness and unique features of these plasmids.
• To explore the implications of plasmid acquisition and evolution in S. sonnei.

Main Methods:

• Plasmid DNA isolation and molecular characterization.
• DNA sequencing and homology analysis.
• Real-time PCR for plasmid copy number determination.
• Transmission electron microscopy for observing cellular effects.

Main Results:

• Three plasmids (pSSE3, pSSE, pSSE2) of ~6 kb were identified in S. sonnei.
• pSSE and pSSE2 showed homology to E. coli E-type colicinogenic plasmids.
• pSSE3 lacked the colicin E8 immunity gene, a novel finding.
• Coexistence of single-stranded and double-stranded DNA was confirmed.
• Plasmid copy number was approximately 20, with observed DNA impairment post-colicin exposure.

Conclusions:

• S. sonnei likely acquired E-group colicin plasmids from E. coli.
• Sequence variations in these plasmids reflect adaptation and cohabitation.
• The unique features of pSSE3 offer insights into colicin plasmid evolution.