Spatial structure and benefits to hosts allow plasmids with and without post-segregational killing systems to coexist

Area of Science:

• Microbiology
• Evolutionary Biology
• Genetics

Background:

• Plasmids are extrachromosomal DNA elements crucial for bacterial adaptation and evolution.
• Post-segregational killing (PSK) systems are plasmid-encoded mechanisms that ensure plasmid inheritance by eliminating plasmid-free daughter cells.
• Previous models suggested that plasmids with PSK systems would competitively exclude plasmids lacking such systems, leading to unstable coexistence.

Purpose of the Study:

• To investigate the conditions under which plasmids with and without PSK systems can stably coexist within bacterial populations.
• To determine the role of spatial structure and plasmid-mediated benefits in plasmid dynamics.

Main Methods:

• Mathematical modeling of plasmid dynamics.
• Simulation of bacterial populations with structured environments.
• Analysis of competition between plasmids with and without PSK systems.

Main Results:

• Spatial structure and plasmid-conferred benefits significantly broaden the conditions for stable plasmid coexistence.
• Plasmids, including those with PSK systems, can provide benefits to their host cells.
• Coexistence is favored when plasmids offer advantages and are present in spatially structured populations.

Conclusions:

• The coexistence of plasmids with and without PSK systems is more common and stable than previously thought, particularly in spatially structured environments.
• The findings suggest that ecological factors, such as spatial organization and resource benefits, play a critical role in shaping plasmid population dynamics.
• These results have broad implications for understanding plasmid evolution and maintenance in natural bacterial communities.