Plasmid-mediated horizontal gene mobilisation: Insights from two lactococcal conjugative plasmids

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Lactococcal strains commonly utilize plasmid conjugation systems, specifically those encoded by pNP40 and pUC11B, for genetic exchange.
• High-frequency mobilization of non-conjugative plasmids by these conjugative systems is crucial for genetic engineering.

Purpose of the Study:

• To identify the genetic elements responsible for the high-frequency mobilization of non-conjugative plasmids mediated by pNP40 and pUC11B.
• To elucidate the molecular mechanisms underlying plasmid mobilization in lactococci.

Main Methods:

• Determination of the origin of transfer (oriT) sequences for plasmids pNP40 and pUC11B.
• Analysis of minimal sequences required for the mobilization of smaller, non-conjugative plasmids.
• Identification and characterization of auxiliary genes, such as mobC, involved in plasmid mobilization.

Main Results:

• The oriT sequences of pNP40 and pUC11B were identified, revealing similar sequences in mobilizable non-conjugative plasmids.
• The auxiliary gene mobC and its functional homologues were found to confer a high-frequency mobilization phenotype.
• Specific genetic determinants underpinning high-frequency plasmid mobilization were pinpointed.

Conclusions:

• The study provides mechanistic insights into lactococcal plasmid conjugation and the mobilization of non-conjugative plasmids.
• Understanding these processes is essential for optimizing strategies for developing improved lactococcal strains for technological applications.