title: Bacterial adaptation to sublethal antibiotic gradients can change the ecological properties of multitrophic microbial communities.
abstract: Antibiotics leak constantly into environments due to widespread use in agriculture and human therapy. Although sublethal concentrations are well known to select for antibiotic-resistant bacteria, little is known about how bacterial evolution cascades through food webs, having indirect effect on species not directly affected by antibiotics (e.g. via population dynamics or pleiotropic effects). Here, we used an experimental evolution approach to test how temporal patterns of antibiotic stress, as well as migration within metapopulations, affect the evolution and ecology of microcosms containing one prey bacterium, one phage and two protist predators. We found that environmental variability, autocorrelation and migration had only subtle effects for population and evolutionary dynamics. However, unexpectedly, bacteria evolved greatest fitness increases to both antibiotics and enemies when the sublethal levels of antibiotics were highest, indicating positive pleiotropy. Crucially, bacterial adaptation cascaded through the food web leading to reduced predator-to-prey abundance ratio, lowered predator community diversity and increased instability of populations. Our results show that the presence of natural enemies can modify and even reverse the effects of antibiotics on bacteria, and that antibiotic selection can change the ecological properties of multitrophic microbial communities by having indirect effects on species not directly affected by antibiotics.
authors.affiliation: Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire SL5 7PY, UK vifriman@gmail.com.
authors.forename: Ville-Petri
authors.identifier: 0000-0002-1592-157X
authors.initials: VP
authors.lastname: Friman
authors.affiliation: Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire SL5 7PY, UK.
authors.forename: Laura Melissa
authors.initials: LM
authors.lastname: Guzman
authors.affiliation: Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire SL5 7PY, UK Department of Ecology and Evolutionary Biology and Kansas Biological Survey, University of Kansas, Lawrence, KS 66047, USA Laboratory of Populations, Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Reuman
authors.affiliation: Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire SL5 7PY, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Bell
mesh_terms: D000220:Adaptation, Biological; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001435:Bacteriophages / Q000502:physiology; D005075:Biological Evolution; D044785:Cryptophyta / Q000502:physiology; D020387:Food Chain; D005839:Gentamicins / Q000494:pharmacology*; D064307:Microbiota / Q000187:drug effects*; D011551:Pseudomonas fluorescens / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D062206:Spatial Analysis; D013769:Tetrahymena pyriformis / Q000502:physiology; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D005839:Gentamicins
keywords: defence; diversity; eco-evolutionary dynamics; environmental change; parasitism; predation
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