title: Coincidental loss of bacterial virulence in multi-enemy microbial communities.
abstract: The coincidental virulence evolution hypothesis suggests that outside-host selection, such as predation, parasitism and resource competition can indirectly affect the virulence of environmentally-growing bacterial pathogens. While there are some examples of coincidental environmental selection for virulence, it is also possible that the resource acquisition and enemy defence is selecting against it. To test these ideas we conducted an evolutionary experiment by exposing the opportunistic pathogen bacterium Serratia marcescens to the particle-feeding ciliate Tetrahymena thermophila, the surface-feeding amoeba Acanthamoeba castellanii, and the lytic bacteriophage Semad11, in all possible combinations in a simulated pond water environment. After 8 weeks the virulence of the 384 evolved clones were quantified with fruit fly Drosophila melanogaster oral infection model, and several other life-history traits were measured. We found that in comparison to ancestor bacteria, evolutionary treatments reduced the virulence in most of the treatments, but this reduction was not clearly related to any changes in other life-history traits. This suggests that virulence traits do not evolve in close relation with these life-history traits, or that different traits might link to virulence in different selective environments, for example via resource allocation trade-offs.
authors.affiliation: Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland; Department of Biological and Environmental Science, University of Helsinki, Helsinki, Finland.
authors.forename: Ji
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland.
authors.forename: Tarmo
authors.initials: T
authors.lastname: Ketola
authors.affiliation: Department of Biological and Environmental Science, University of Helsinki, Helsinki, Finland.
authors.forename: Anni-Maria
authors.initials: AM
authors.lastname: Örmälä-Odegrip
authors.affiliation: Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland.
authors.forename: Johanna
authors.initials: J
authors.lastname: Mappes
authors.affiliation: Centre of Excellence in Biological Interactions, Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä, Finland; Department of Biological and Environmental Science, University of Helsinki, Helsinki, Finland.
authors.forename: Jouni
authors.initials: J
authors.lastname: Laakso
mesh_terms: D048248:Acanthamoeba castellanii / Q000235:genetics / Q000472:pathogenicity; D001435:Bacteriophages / Q000235:genetics / Q000472:pathogenicity; D019143:Evolution, Molecular; D059013:Microbial Consortia / Q000235:genetics*; D012706:Serratia marcescens / Q000235:genetics / Q000472:pathogenicity; D037521:Virulence Factors / Q000235:genetics*
chemical_list: D037521:Virulence Factors