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Antagonistic competition moderates virulence in Bacillus thuringiensis.
Jennie Garbutt1, Michael B Bonsall, Denis J Wright
1Mathematical Ecology Research Group, Department of Zoology, University of Oxford, South Parks Road, Oxford, OX1 3PS, UK.
Ecology Letters
|June 4, 2011
Summary
In bacterial pathogen evolution, mixed infections can favor antagonism over virulence. This study shows Bacillus thuringiensis in mixed infections evolved increased antagonism, leading to reduced virulence and pathogen growth.
Area of Science:
- Evolutionary biology
- Microbial pathogenesis
- Parasite ecology
Background:
- Classical models predict multiple infections increase pathogen virulence.
- However, diverse parasite competition modes can alter virulence evolution.
- The role of antagonism in mixed-strain infections remains understudied.
Purpose of the Study:
- To investigate if selection in mixed-strain infections promotes antagonism.
- To determine if increased antagonism trades off against virulence.
- To examine the impact of mixed infections on pathogen competitiveness.
Main Methods:
- Experimental evolution of Bacillus thuringiensis under single-strain and mixed-strain conditions.
- Quantification of bacterial antagonism and virulence.
- Measurement of pathogen growth in vitro and in vivo.
Main Results:
- Mixed-strain selection enhanced competitor suppression (antagonism) in Bacillus thuringiensis.
- Increased antagonism correlated with decreased virulence in most selected lines.
- Mixed infections exhibited lower virulence and reduced pathogen growth compared to single-strain infections.
Conclusions:
- Selection in mixed infections can favor antagonism, leading to reduced virulence.
- Spiteful interactions may be advantageous due to metabolic costs of virulence and risks of mixed infections.
- Findings challenge classical virulence evolution models by highlighting the impact of competition mode.
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