title: Killing niche competitors by remote-control bacteriophage induction.
abstract: A surprising example of interspecies competition is the production by certain bacteria of hydrogen peroxide at concentrations that are lethal for others. A case in point is the displacement of Staphylococcus aureus by Streptococcus pneumoniae in the nasopharynx, which is of considerable clinical significance. How it is accomplished, however, has been a great mystery, because H(2)O(2) is a very well known disinfectant whose lethality is largely due to the production of hyperoxides through the abiological Fenton reaction. In this report, we have solved the mystery by showing that H(2)O(2) at the concentrations typically produced by pneumococci kills lysogenic but not nonlysogenic staphylococci by inducing the SOS response. The SOS response, a stress response to DNA damage, not only invokes DNA repair mechanisms but also induces resident prophages, and the resulting lysis is responsible for H(2)O(2) lethality. Because the vast majority of S. aureus strains are lysogenic, the production of H(2)O(2) is a very widely effective antistaphylococcal strategy. Pneumococci, however, which are also commonly lysogenic and undergo SOS induction in response to DNA-damaging agents such as mitomycin C, are not SOS-induced on exposure to H(2)O(2). This is apparently because they are resistant to the DNA-damaging effects of the Fenton reaction. The production of an SOS-inducing signal to activate prophages in neighboring organisms is thus a rather unique competitive strategy, which we suggest may be in widespread use for bacterial interference. However, this strategy has as a by-product the release of active phage, which can potentially spread mobile genetic elements carrying virulence genes.
authors.affiliation: Universidad Cardenal Herrera-CEU, 46113 Moncada, Valencia, Spain.
authors.forename: Laura
authors.initials: L
authors.lastname: Selva
authors.forename: David
authors.initials: D
authors.lastname: Viana
authors.forename: Gili
authors.initials: G
authors.lastname: Regev-Yochay
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Trzcinski
authors.forename: Juan Manuel
authors.initials: JM
authors.lastname: Corpa
authors.forename: Iñigo
authors.initials: I
authors.lastname: Lasa
authors.forename: Richard P
authors.initials: RP
authors.lastname: Novick
authors.forename: José R
authors.initials: JR
authors.lastname: Penadés
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000956:Antigens, Viral / Q000378:metabolism; D001435:Bacteriophages / Q000187:drug effects / Q000276:immunology / Q000502:physiology*; D002374:Catalase / Q000378:metabolism; D018920:Coculture Techniques; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008242:Lysogeny / Q000187:drug effects; D050296:Microbial Viability / Q000187:drug effects; D016685:Mitomycin / Q000494:pharmacology; D013014:SOS Response, Genetics / Q000187:drug effects; D013211:Staphylococcus aureus / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000821:virology*; D013296:Streptococcus pneumoniae / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology / Q000821:virology*; D014775:Virus Activation / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D000956:Antigens, Viral; D016685:Mitomycin; D006861:Hydrogen Peroxide; D002374:Catalase