Selection for plasmid post–segregational killing depends on multiple infection: evidence for the selection of more virulent parasites through parasite–level competition

Is the virulence of parasites an outcome of optimized infection? Virulence has often been considered an inevitable consequence of parasite reproduction when the cost incurred by the parasite in reducing the fitness of its current host is offset by increased infection of new hosts. More recent models...

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Bibliographic Details
Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2005-02, Vol.272 (1561), p.403-410
Main Authors: Cooper, T. F., Heinemann, J. A.
Format: Article
Language:English
Subjects:
Animals
Bacteria
Bacteria - genetics
Bacteria - growth & development
Between-Host Virulence
Biological competition
Colony Count, Microbial
Competitive Behavior - physiology
Conjugative Plasmids
Ecological competition
Evolution
Horizontal transmission
Host-Parasite Interactions
Modeling
Models, Biological
Multiple Infection
Parasite hosts
Parasites
Parasites - pathogenicity
Plasmids
Plasmids - genetics
Plasmids - physiology
Population Dynamics
Post-Segregational Killing
Selection, Genetic
Time Factors
Virulence
Within-Host Virulence
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Summary:Is the virulence of parasites an outcome of optimized infection? Virulence has often been considered an inevitable consequence of parasite reproduction when the cost incurred by the parasite in reducing the fitness of its current host is offset by increased infection of new hosts. More recent models have focused on how competition occurring between parasites during co-infection might effect selection of virulence. For example, if co-infection was common, parasites with higher intrinsic growth rates might be selected, even at the expense of being optimally adapted to infect new hosts. If growth rate is positively correlated with virulence, then competition would select increased virulence. We tested these models using a plasmid-encoded virulence determinant. The virulence determinant did not contribute to the plasmid's reproduction within or between hosts. Despite this, virulent plasmids were more successful than avirulent derivatives during selection in an environment allowing within-host competition. To explain these findings we propose and test a model in which virulent parasites are selected by reducing the reproduction of competitors.
ISSN:0962-8452
1471-2954
DOI:10.1098/rspb.2004.2921