Parasitic plasmid-host dynamics and host competition in flowing habitats

Area of Science:

• Microbiology
• Evolutionary Biology
• Systems Biology

Background:

• Bacterial species competition is a key factor in microbial ecology.
• Parasitic plasmids can reduce host fitness but may influence population dynamics.
• Understanding factors promoting species coexistence is crucial for microbial community stability.

Purpose of the Study:

• To investigate how parasitic plasmids affect the competition and coexistence of bacterial species.
• To determine the conditions under which plasmids can mediate the coexistence of competing bacterial hosts.
• To model bacterial population dynamics in a simulated gut environment.

Main Methods:

• Numerical simulations were employed to model bacterial populations in a flow reactor.
• The model incorporated vertical plasmid transmission with potential segregation (loss).
• Fitness reduction in hosts was attributed to a plasmid-encoded toxin inhibiting plasmid-free cells.

Main Results:

• Parasitic plasmids were shown to mediate the coexistence of competing bacterial species.
• Coexistence was observed in conditions where plasmid-free hosts could not coexist.
• Successful coexistence was dependent on a narrow parameter range, requiring low segregation and growth costs.

Conclusions:

• Parasitic plasmids can act as a stabilizing factor in microbial communities, promoting species coexistence.
• The ability of plasmids to facilitate coexistence is sensitive to the rates of plasmid loss and the fitness cost of plasmid carriage.
• These findings highlight the complex interplay between host competition, parasitic elements, and environmental conditions in shaping microbial populations.