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Open Access Research article

Antagonistic interactions peak at intermediate genetic distance in clinical and laboratory strains of Pseudomonas aeruginosa

Sijmen E Schoustra12*, Jonathan Dench1, Rola Dali1, Shawn D Aaron3 and Rees Kassen1

Author Affiliations

1 Biology Department, University of Ottawa, 30 Marie Curie, Ottawa, ON K1N 6N5, Canada

2 Laboratory of Genetics, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, the Netherlands

3 Ottawa Health Research Institute, 725 Parkdale Ave, Ottawa, ON K1Y 4E9, Canada

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BMC Microbiology 2012, 12:40  doi:10.1186/1471-2180-12-40

Published: 22 March 2012

Abstract

Background

Bacteria excrete costly toxins to defend their ecological niche. The evolution of such antagonistic interactions between individuals is expected to depend on both the social environment and the strength of resource competition. Antagonism is expected to be weak among highly similar genotypes because most individuals are immune to antagonistic agents and among dissimilar genotypes because these are unlikely to be competing for the same resources and antagonism should not yield much benefit. The strength of antagonism is therefore expected to peak at intermediate genetic distance.

Results

We studied the ability of laboratory strains of Pseudomonas aeruginosa to prevent growth of 55 different clinical P. aeruginosa isolates derived from cystic fibrosis patients. Genetic distance was determined using genetic fingerprints. We found that the strength of antagonism was maximal among genotypes of intermediate genetic distance and we show that genetic distance and resource use are linked.

Conclusions

Our results suggest that the importance of social interactions like antagonism may be modulated by the strength of resource competition.