Predators promote defence of rhizosphere bacterial populations by selective feeding on non-toxic cheaters.

Details

Serval ID
serval:BIB_0CCE9B3F3600
Type
Article: article from journal or magazin.
Collection
Publications
Title
Predators promote defence of rhizosphere bacterial populations by selective feeding on non-toxic cheaters.
Journal
The ISME Journal
Author(s)
Jousset A., Rochat L., Péchy-Tarr M., Keel C., Scheu S., Bonkowski M.
ISSN
1751-7370[electronic], 1751-7362[linking]
Publication state
Published
Issued date
2009
Peer-reviewed
Oui
Volume
3
Number
6
Pages
666-674
Language
english
Abstract
Soil pseudomonads increase their competitiveness by producing toxic secondary metabolites, which inhibit competitors and repel predators. Toxin production is regulated by cell-cell signalling and efficiently protects the bacterial population. However, cell communication is unstable, and natural populations often contain signal blind mutants displaying an altered phenotype defective in exoproduct synthesis. Such mutants are weak competitors, and we hypothesized that their fitness depends on natural communities on the exoproducts of wild-type bacteria, especially defence toxins. We established mixed populations of wild-type and signal blind, non-toxic gacS-deficient mutants of Pseudomonas fluorescens CHA0 in batch and rhizosphere systems. Bacteria were grazed by representatives of the most important bacterial predators in soil, nematodes (Caenorhabditis elegans) and protozoa (Acanthamoeba castellanii). The gacS mutants showed a negative frequency-dependent fitness and could reach up to one-third of the population, suggesting that they rely on the exoproducts of the wild-type bacteria. Both predators preferentially consumed the mutant strain, but populations with a low mutant load were resistant to predation, allowing the mutant to remain competitive at low relative density. The results suggest that signal blind Pseudomonas increase their fitness by exploiting the toxins produced by wild-type bacteria, and that predation promotes the production of bacterial defence compounds by selectively eliminating non-toxic mutants. Therefore, predators not only regulate population dynamics of soil bacteria but also structure the genetic and phenotypic constitution of bacterial communities.
Keywords
Acanthamoeba castellanii/physiology, Animals, Bacterial Proteins/genetics, Bacterial Proteins/metabolism, Bacterial Toxins/metabolism, Caenorhabditis elegans/physiology, Feeding Behavior, Gene Deletion, Pseudomonas fluorescens/growth & development, Pseudomonas fluorescens/physiology, Signal Transduction, Soil Microbiology
Pubmed
Web of science
Open Access
Yes
Create date
04/03/2009 16:22
Last modification date
20/08/2019 13:34
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