RESUMEN
A DNA containing bacteriophage, Kvp1, was isolated from the water of a very polluted river, the Matanza river, near the central district of Buenos Aires City. This bacteriophage infects bacteria belonging to the Kluyvera cryocrescens species (strain 21 g) isolated from the same river. Kvp1 is a lytic bacteriophage and its propagation characteristics are: burst size 30, latent period 13 min and rise period 10 min. Morphologically, Kvp1 is a small icosahedral bacteriophage, 59.1 nm in diameter, which possesses a short wedge-shaped tail. Its buoyant density in ClCs is 1.517 g/cm3. Kvp1 DNA is linear, double stranded and approximately 40,000 bp in size. The viral particle is composed of at least nine proteins. SDS-PAGE patterns of these proteins and of those produced during the host infection, in addition to its morphological and genomic characteristics, suggested that Kvp1 is similar to the coliphage T7. Molecular cloning, sequencing and computer-assisted analysis of Kvp1 DNA fragments confirmed the relationship to the coliphage. Taking this into account, the partial sequence of the phage RNA polymerase was used to construct phylogenetic relationships between Kvp1 and other related phages. To our knowledge, Kvp1 is the first bacteriophage described which uses as host a member of the Kluyvera bacterial genus.
Asunto(s)
Bacteriófagos , Enterobacteriaceae/virología , Bacteriófago T7/clasificación , Bacteriófago T7/genética , Bacteriófagos/genética , Bacteriófagos/aislamiento & purificación , Bacteriófagos/ultraestructura , ADN/análisis , ADN Viral/análisis , ADN Viral/química , Genoma Viral , Microscopía Electrónica , Datos de Secuencia Molecular , Filogenia , Podoviridae/clasificación , Podoviridae/genética , Proteínas Virales/análisis , Proteínas Virales/químicaRESUMEN
Plasmid pPG1 from Staphylococcus aureus coding for ampicillin (Apr), gentamicin (Gmr) and amikacin (Akr) resistance was transformed into Escherichia coli. Transformation efficiency was about 2 x 10(3) transformants/micrograms of plasmid DNA. The plasmids present in the E. coli transformants were identical to pPG1 according to their restriction patterns. The copy number of pPG1 was estimated to be at least 20-times less in E. coli than in S. aureus. The minimal inhibitory concentrations (MICs) for Ap and Gm were lower in E. coli than in S. aureus. However, the MIC for Ak was higher in E. coli transformants than in S. aureus. pPG1 was maintained in the E. coli transformants for at least 80 generations at 37 degrees C without antibiotic selection pressure.