Symbiont evolution during the free-living phase can improve host colonization
William Soto1, Michael Travisano2,3, Alexandra Rose Tolleson1
11College of William & Mary, Department of Biology, Integrated Science Center Rm 3035, 540 Landrum Dr Williamsburg, VA 23185, USA.
Microbiology (Reading, England)
|January 17, 2019
Summary
Evolution in the free-living stage enhances microbial fitness in host environments. Free-living microbial evolution outside the host promoted host range expansion and improved colonization for Vibrio fischeri.
Area of Science:
- Microbial Ecology
- Evolutionary Biology
- Symbiosis
Background:
- Microorganisms alternate between free-living and host-associated stages.
- Reproduction occurs in both lifestyles, raising questions about evolutionary trade-offs.
- Understanding free-living evolution's impact on host fitness is crucial for symbiosis.
Purpose of the Study:
- To investigate if evolution during the free-living stage benefits microbial fitness within a host.
- To determine if free-living microbial evolution can positively impact host colonization and range.
- To assess the reproducibility of these effects across diverse genetic backgrounds.
Main Methods:
- Used the squid Euprymna tasmanica and Vibrio fischeri symbiont model.
- Simulated free-living microbial evolution via ecological diversification in static liquid microcosms.
- Examined thirteen genetically distinct V. fischeri strains from various ecological sources.
Main Results:
- New mutations facilitating host colonization rapidly emerged during free-living evolution for all strains.
- Microbial evolution outside the host environment enhanced host range expansion.
- Improved host colonization and reduced negative correlations between biofilm formation and motility were observed.
Conclusions:
- Free-living microbial evolution can be strongly beneficial for host colonization and fitness.
- The observed benefits are largely independent of the specific genetic background of the microbe.
- Evolutionary pressures in a free-living state can prime microbes for successful host association.
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