Acquisition of a second multi-drug resistance-encoding element by IncM1 plasmid pACM130 abolished conjugative...

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• The IncM plasmid family includes members with a specific lineage characterized by a Tn1721-based multiple-resistance island inserted into the mucB gene.
• Previously identified plasmids in this group include R1215, p202c, pIGT15, pARM26, and pACM1, isolated from Europe and the USA.

Purpose of the Study:

• To characterize a novel IncM plasmid, pACM130, identified from an American hospital.
• To investigate the genetic basis for the altered conjugative phenotype of pACM130.

Main Methods:

• Plasmid isolation and characterization.
• Genetic analysis to identify inserted transposons and their locations.
• Conjugation experiments to assess plasmid transfer capability.
• Mobilization assays using a laboratory-derived vector expressing the traY gene.

Main Results:

• pACM130, a new IncM plasmid, was isolated and found to possess a Tn1721-based resistance island similar to other members of its lineage.
• A copy of the Tn1331 transposon was identified within pACM130, specifically interrupting the traY gene, which is crucial for conjugation.
• The interruption of the traY gene resulted in the abolition of pACM130's conjugative phenotype.
• Plasmid pACM130 could be mobilized by providing a functional traY gene through transformation with a laboratory vector.

Conclusions:

• The IncM plasmid pACM130 represents a new member of a specific plasmid lineage, carrying both Tn1721-based resistance and Tn1331 elements.
• The insertion of Tn1331 into the traY gene is responsible for the loss of conjugation in pACM130.
• This finding highlights the dynamic nature of plasmid genomes and the impact of transposon activity on plasmid function and transferability.