title: Characterization of a phage-like pyocin from the plant growth-promoting rhizobacterium Pseudomonas fluorescens SF4c.
abstract: R-type and F-type pyocins are high-molecular-mass bacteriocins produced by Pseudomonas aeruginosa that resemble bacteriophage tails. They contain no head structures and no DNA, and are used as defence systems. In this report, we show that Pseudomonas fluorescens SF4c, a strain isolated from the wheat rhizosphere, produces a high-molecular-mass bacteriocin which inhibits the growth of closely related bacteria. A mutant deficient in production of this antimicrobial compound was obtained by transposon mutagenesis. Sequence analysis revealed that the transposon had disrupted a gene that we have named ptm, since it is homologous to that encoding phage tape-measure protein in P. fluorescens Pf0-1, a gene belonging to a prophage similar to phage-like pyocin from P. aeruginosa PAO1. In addition, we have identified genes from the SF4c pyocin cluster that encode a lytic system and regulatory genes. We constructed a non-polar ptm mutant of P. fluorescens SF4c. Heterologous complementation of this mutation restored the production of bacteriocin. Real-time PCR was used to analyse the expression of pyocin under different stress conditions. Bacteriocin was upregulated by mitomycin C, UV light and hydrogen peroxide, and was downregulated by saline stress. This report constitutes, to our knowledge, the first genetic characterization of a phage tail-like bacteriocin in a rhizosphere Pseudomonas strain.
authors.affiliation: Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain.|Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Ruta 36-Km 601-5800, Río Cuarto-Córdoba, Argentina.
authors.forename: Sonia
authors.initials: S
authors.lastname: Fischer
authors.affiliation: Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Ruta 36-Km 601-5800, Río Cuarto-Córdoba, Argentina.
authors.forename: Agustina
authors.initials: A
authors.lastname: Godino
authors.affiliation: Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain.
authors.forename: José Miguel
authors.initials: JM
authors.lastname: Quesada
authors.affiliation: Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Ruta 36-Km 601-5800, Río Cuarto-Córdoba, Argentina.
authors.forename: Paula
authors.initials: P
authors.lastname: Cordero
authors.affiliation: Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Ruta 36-Km 601-5800, Río Cuarto-Córdoba, Argentina.
authors.forename: Edgardo
authors.initials: E
authors.lastname: Jofré
authors.affiliation: Facultad de Ciencias Exactas, Físico-Químicas y Naturales, Universidad Nacional de Río Cuarto, Ruta 36-Km 601-5800, Río Cuarto-Córdoba, Argentina.
authors.forename: Gladys
authors.initials: G
authors.lastname: Mori
authors.affiliation: Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas (CSIC), Granada, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Espinosa-Urgel
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D001435:Bacteriophages / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011551:Pseudomonas fluorescens / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D011709:Pyocins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism* / Q000494:pharmacology; D058441:Rhizosphere; D012988:Soil Microbiology; D014908:Triticum / Q000254:growth & development / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D011709:Pyocins