title: Genetic drift suppresses bacterial conjugation in spatially structured populations.
abstract: Conjugation is the primary mechanism of horizontal gene transfer that spreads antibiotic resistance among bacteria. Although conjugation normally occurs in surface-associated growth (e.g., biofilms), it has been traditionally studied in well-mixed liquid cultures lacking spatial structure, which is known to affect many evolutionary and ecological processes. Here we visualize spatial patterns of gene transfer mediated by F plasmid conjugation in a colony of Escherichia coli growing on solid agar, and we develop a quantitative understanding by spatial extension of traditional mass-action models. We found that spatial structure suppresses conjugation in surface-associated growth because strong genetic drift leads to spatial isolation of donor and recipient cells, restricting conjugation to rare boundaries between donor and recipient strains. These results suggest that ecological strategies, such as enforcement of spatial structure and enhancement of genetic drift, could complement molecular strategies in slowing the spread of antibiotic resistance genes.
authors.affiliation: FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Freese
authors.affiliation: FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts; Department of Physics, Harvard University, Cambridge, Massachusetts; Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts; Department of Physics and Program in Bioinformatics, Boston University, Boston, Massachusetts.
authors.forename: Kirill S
authors.initials: KS
authors.lastname: Korolev
authors.affiliation: FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts; Faculty of Health and Medical Sciences, University of Surrey, United Kingdom.
authors.forename: José I
authors.initials: JI
authors.lastname: Jiménez
authors.affiliation: FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts; Department of Chemistry and Biochemistry, Program in Biomolecular Sciences and Engineering, University of California at Santa Barbara, Santa Barbara, California. Electronic address: chen@chem.ucsb.edu.
authors.forename: Irene A
authors.initials: IA
authors.lastname: Chen
mesh_terms: D003227:Conjugation, Genetic; D004926:Escherichia coli / Q000235:genetics* / Q000502:physiology; D005144:F Factor / Q000235:genetics; D040961:Genetic Drift; D008957:Models, Genetic