Current address: Department of Ecology & Evolutionary Biology, Rice University, 6100 S. Main Street, Houston, Texas 77005-1892.
SUPERINFECTION DRIVES VIRULENCE EVOLUTION IN EXPERIMENTAL POPULATIONS OF BACTERIA AND PLASMIDS
Article first published online: 20 NOV 2010
© 2010 The Author(s). Evolution© 2010 The Society for the Study of Evolution.
Volume 65, Issue 3, pages 831–841, March 2011
How to Cite
smith, j. (2011), SUPERINFECTION DRIVES VIRULENCE EVOLUTION IN EXPERIMENTAL POPULATIONS OF BACTERIA AND PLASMIDS. Evolution, 65: 831–841. doi: 10.1111/j.1558-5646.2010.01178.x
- Issue published online: 1 MAR 2011
- Article first published online: 20 NOV 2010
- Accepted manuscript online: 5 NOV 2010 04:54AM EST
- Received March 28, 2010, Accepted September 27, 2010
- Horizontal gene transfer;
- host–parasite evolution;
- selfish genetic elements;
- vertical transmission
A prominent hypothesis proposes that pathogen virulence evolves in large part due to a trade-off between infectiousness and damage to hosts. Other explanations emphasize how virulence evolves in response to competition among pathogens within hosts. Given the proliferation of theoretical possibilities, what best predicts how virulence evolves in real biological systems? Here, I show that virulence evolution in experimental populations of bacteria and self-transmissible plasmids is best explained by within-host competition. Plasmids evolved to severely reduce the fitness of their hosts even in the absence of uninfected cells. This result is inconsistent with the trade-off hypothesis, which predicts that under these conditions vertically transmitted pathogens would evolve to be less virulent. Plasmid virulence was strongly correlated with the ability to superinfect cells containing competing plasmid genotypes, suggesting a key role for within-host competition. When virulent genotypes became common, hosts evolved resistance to plasmid infection. These results show that the trade-off hypothesis can incorrectly predict virulence evolution when within-host interactions are neglected. They also show that symbioses between bacteria and plasmids can evolve to be surprisingly antagonistic.