Methods for detection of conjugative plasmid transfer in aquatic environments

Area of Science:

• Microbiology
• Environmental Science
• Molecular Biology

Background:

• Bacterial conjugation is a key mechanism for horizontal gene transfer.
• Efficient counter selection methods are crucial for tracking plasmid transfer in various environments.
• Assessing the efficacy of different counter selection strategies is vital for ecological and genetic studies.

Purpose of the Study:

• To evaluate and compare three distinct bacterial counter selection systems for plasmid RP4 transfer.
• To determine the efficiency of these systems in both filter mating and lake water microcosm experiments.
• To identify the most suitable counter selection method for microbial ecology studies.

Main Methods:

• Investigated three counter selection systems: antibiotic-resistant recipients, auxotrophic donors, and donors with chromosomal suicide genes.
• Performed bacterial conjugation experiments on filters and in lake water microcosms.
• Quantified transfer efficiencies of transconjugants per recipient.

Main Results:

• No significant difference in transfer efficiencies between the three systems in filter matings.
• Some nalidixic acid-resistant recipients showed partial sensitivity post-plasmid reception.
• Auxotrophic donors proved effective and simple for recovering indigenous transconjugants.
• Suicide gene elimination of donors succeeded in filter matings but failed in microcosms.

Conclusions:

• Auxotrophic donor systems offer a practical approach for recovering transconjugants in conjugation studies.
• Suicide gene-based counter selection is not reliable for donor elimination in complex microcosm environments.
• The choice of counter selection method should consider the experimental system, particularly for environmental applications.