title: Coevolution with bacteriophages drives genome-wide host evolution and constrains the acquisition of abiotic-beneficial mutations.
abstract: Studies of antagonistic coevolution between hosts and parasites typically focus on resistance and infectivity traits. However, coevolution could also have genome-wide effects on the hosts due to pleiotropy, epistasis, or selection for evolvability. Here, we investigate these effects in the bacterium Pseudomonas fluorescens SBW25 during approximately 400 generations of evolution in the presence or absence of bacteriophage (coevolution or evolution treatments, respectively). Coevolution resulted in variable phage resistance, lower competitive fitness in the absence of phages, and greater genome-wide divergence both from the ancestor and between replicates, in part due to the evolution of increased mutation rates. Hosts from coevolution and evolution treatments had different suites of mutations. A high proportion of mutations observed in coevolved hosts were associated with a known phage target binding site, the lipopolysaccharide (LPS), and correlated with altered LPS length and phage resistance. Mutations in evolved bacteria were correlated with higher fitness in the absence of phages. However, the benefits of these growth-promoting mutations were completely lost when these bacteria were subsequently coevolved with phages, indicating that they were not beneficial in the presence of resistance mutations (consistent with negative epistasis). Our results show that in addition to affecting genome-wide evolution in loci not obviously linked to parasite resistance, coevolution can also constrain the acquisition of mutations beneficial for growth in the abiotic environment.
authors: Department of Zoology, University of Oxford, Oxford, United Kingdom pauline.scanlan@teagasc.ie paulinescanlan@yahoo.co.uk.
authors: Pauline D
authors: PD
authors: Scanlan
authors: Department of Zoology, University of Oxford, Oxford, United Kingdom.
authors: Alex R
authors: AR
authors: Hall
authors: Central Pathology Laboratory, Department of Histopathology and Morbid Anatomy, School of Medicine, Trinity College, Dublin, Ireland.
authors: Gordon
authors: G
authors: Blackshields
authors: Department of Zoology, University of Oxford, Oxford, United Kingdom.
authors: Ville-P
authors: VP
authors: Friman
authors: Department of Microbiology, Immunology and Cancer Biology, University of Virginia Health System, Charlottesville, VA.
authors: Michael R
authors: MR
authors: Davis
authors: Department of Microbiology, Immunology and Cancer Biology, University of Virginia Health System, Charlottesville, VA.
authors: Joanna B
authors: JB
authors: Goldberg
authors: Department of Zoology, University of Oxford, Oxford, United Kingdom.
authors: Angus
authors: A
authors: Buckling
mesh_terms: D004269:DNA, Bacterial / Q000235:genetics; D004279:DNA, Viral / Q000235:genetics; D019143:Evolution, Molecular; D056726:Genetic Association Studies; D014644:Genetic Variation; D016680:Genome, Bacterial; D005838:Genotype; D010641:Phenotype; D017105:Pseudomonas Phages / Q000235:genetics*; D011551:Pseudomonas fluorescens / Q000235:genetics* / Q000821:virology; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D004279:DNA, Viral
keywords: antagonistic coevolution; bacteria; bacteriophage; experimental evolution; molecular evolution