Life History Trade-Offs and Relaxed Selection Can Decrease Bacterial Virulence in Environmental Reservoirs
Abstract
Pathogen virulence is usually thought to evolve in reciprocal selection with the host. While this might be true for obligate pathogens, the life histories of opportunistic pathogens typically alternate between within-host and outside-host environments during the infection-transmission cycle. As a result, opportunistic pathogens are likely to experience conflicting selection pressures across different environments, and this could affect their virulence through life-history trait correlations. We studied these correlations experimentally by exposing an opportunistic bacterial pathogen Serratia marcescens to its natural protist predator Tetrahymena thermophila for 13 weeks, after which we measured changes in bacterial traits related to both anti-predator defence and virulence. We found that anti-predator adaptation (producing predator-resistant biofilm) caused a correlative attenuation in virulence. Even though the direct mechanism was not found, reduction in virulence was most clearly connected to a predator-driven loss of a red bacterial pigment, prodigiosin. Moreover, life-history trait evolution was more divergent among replicate populations in the absence of predation, leading also to lowered virulence in some of the ‘predator absent’ selection lines. Together these findings suggest that the virulence of non-obligatory, opportunistic bacterial pathogens can decrease in environmental reservoirs through life history trade-offs, or random accumulation of mutations that impair virulence traits under relaxed selection.
Main Authors
Format
Articles
Research article
Published
2012
Series
Subjects
Publication in research information system
Publisher
Public Library of Science
Original source
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0043801
The permanent address of the publication
https://urn.fi/URN:NBN:fi:jyu-201401011000Use this for linking
Review status
Peer reviewed
ISSN
1932-6203
DOI
https://doi.org/10.1371/journal.pone.0043801
Language
English
Published in
PLoS One
Citation
- Mikonranta, L., Friman, V.-P., & Laakso, J. (2012). Life History Trade-Offs and Relaxed Selection Can Decrease Bacterial Virulence in Environmental Reservoirs. PLoS One, 7(8). https://doi.org/10.1371/journal.pone.0043801
Copyright© Mikonranta et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.