title: The weak shall inherit: bacteriocin-mediated interactions in bacterial populations.
abstract: BACKGROUND
  Evolutionary arms race plays a major role in shaping biological diversity. In microbial systems, competition often involves chemical warfare and the production of bacteriocins, narrow-spectrum toxins aimed at killing closely related strains by forming pores in their target's membrane or by degrading the target's RNA or DNA. Although many empirical and theoretical studies describe competitive exclusion of bacteriocin-sensitive strains by producers of bacteriocins, the dynamics among producers are largely unknown.
  
  
  RESULTS
  We used a reporter-gene assay to show that the bacterial response to bacteriocins' treatment mirrors the inflicted damage Potent bacteriocins are lethal to competing strains, but at sublethal doses can serve as strong inducing agents, enhancing their antagonists' bacteriocin production. In contrast, weaker bacteriocins are less toxic to their competitors and trigger mild bacteriocin expression. We used empirical and numerical models to explore the role of cross-induction in the arms race between bacteriocin-producing strains. We found that in well-mixed, unstructured environments where interactions are global, producers of weak bacteriocins are selectively advantageous and outcompete producers of potent bacteriocins. However, in spatially structured environments, where interactions are local, each producer occupies its own territory, and competition takes place only in "no man's lands" between territories, resulting in much slower dynamics.
  
  
  CONCLUSIONS
  The models we present imply that producers of potent bacteriocins that trigger a strong response in neighboring bacteriocinogenic strains are doomed, while producers of weak bacteriocins that trigger a mild response in bacteriocinogenic strains flourish. This counter-intuitive outcome might explain the preponderance of weak bacteriocin producers in nature. However, the described scenario is prolonged in spatially structured environments thus promoting coexistence, allowing migration and evolution, and maintaining bacterial diversity.
authors.affiliation: Zuckerberg Institute for Water Research, J. Blaustein Institutes for Desert Research, Ben-Gurion University, Sede Boqer Campus, Midreshet Ben-Gurion, Israel.
authors.forename: Hadeel
authors.initials: H
authors.lastname: Majeed
authors.forename: Adam
authors.initials: A
authors.lastname: Lampert
authors.forename: Lusine
authors.initials: L
authors.lastname: Ghazaryan
authors.forename: Osnat
authors.initials: O
authors.lastname: Gillor
mesh_terms: D001419:Bacteria / Q000187:drug effects / Q000378:metabolism*; D001430:Bacteriocins / Q000378:metabolism*; D044822:Biodiversity; D003087:Colicins / Q000633:toxicity; D003198:Computer Simulation; D017930:Genes, Reporter
chemical_list: D001430:Bacteriocins; D003087:Colicins