The dilution effect limits plasmid horizontal transmission in multispecies bacterial communities

Area of Science:

• Microbial Ecology
• Evolutionary Biology
• Genetics

Background:

• Plasmids facilitate trait transfer, driving bacterial evolution and genomic divergence.
• Understanding plasmid dynamics in diverse microbial communities is crucial but remains poorly understood.
• Coexistence of multiple plasmids within bacterial communities presents complex transmission challenges.

Purpose of the Study:

• To investigate the impact of bacterial and plasmid diversity on horizontal plasmid transmission.
• To elucidate the mechanisms limiting plasmid spread in multi-species bacterial communities.
• To assess the role of the 'dilution effect' in plasmid dynamics.

Main Methods:

• Construction of experimental multi-species bacterial communities with two distinct plasmids.
• Quantification of horizontal plasmid transmission rates across varying bacterial diversity.
• Analysis of plasmid conjugation rates in the presence of co-infecting plasmids.

Main Results:

• Increased bacterial diversity significantly limited horizontal plasmid transmission via the 'dilution effect'.
• The presence of multiple plasmids within host cells reduced the overall rate of plasmid conjugation.
• Plasmid spread is constrained by both host community diversity and plasmid-plasmid interactions.

Conclusions:

• Bacterial diversity acts as a barrier to plasmid transmission through the dilution effect.
• Plasmid-plasmid interactions, particularly in co-infected cells, further impede horizontal gene transfer.
• These findings highlight key factors regulating plasmid dynamics and evolution in complex microbial ecosystems.