Conjugative plasmid mediated inducible nickel resistance in Hafnia alvei 5-5.

Hafnia alvei 5-5, isolated from a soil-litter mixture underneath the canopy of the nickel-hyperaccumulating tree Sebertia acuminata (Sapotaceae) in New Caledonia, was found to be resistant to 30 mM Ni(2+) or 2 mM Co(2+). The 70-kb plasmid, pEJH 501, was transferred by conjugation to Escherichia coli, Serratia marcescens, and Klebsiella oxytoca. Transconjugant strains expressed inducible nickel resistance to between 5 and 17 mM Ni(2+), and cobalt resistance to 2 mM Co(2+). A 4.8-kb Sal- EcoRI fragment containing the nickel resistance determinant was subcloned, and the hybrid plasmid was found to confer a moderate level of resistance to nickel (7 mM Ni(2+)) even to E. coli. The expression of nickel resistance was inducible by exposure to nickel chloride at a concentration as low as 0.5 mM Ni(2+). By random Tn phoA'-1 insertion mutagenesis, the fragment was shown to have structural genes as well as regulatory regions for nickel resistance. Southern hybridization studies showed that the nickel-resistance determinant from pEJH501 of H. alvei 5-5 was homologous to that of pTOM9 from Alcaligenes xylosoxydans 31A.

Conjugative plasmid pEJH501-mediated inducible nickel resistance in Hafnia alvei 5-5 / Resistencia al níquel en Hafnia alvei 5-5 mediada por el plásmido conjugativo pEJH501

Hafnia alvei 5-5, isolated from a soil-litter mixture underneath the canopy of the nickel-hyperaccumulating tree Sebertia acuminata (Sapotaceae) in New Caledonia, was found to be resistant to 30 mM Ni(2+) or 2 mM Co(2+). The 70-kb plasmid, pEJH 501, was transferred by conjugation to Escherichia coli, Serratia marcescens, and Klebsiella oxytoca. Transconjugant strains expressed inducible nickel resistance to between 5 and 17 mM Ni(2+), and cobalt resistance to 2 mM Co(2+). A 4.8-kb Sal- EcoRI fragment containing the nickel resistance determinant was subcloned, and the hybrid plasmid was found to confer a moderate level of resistance to nickel (7 mM Ni(2+)) even to E. coli. The expression of nickel resistance was inducible by exposure to nickel chloride at a concentration as low as 0.5 mM Ni(2+). By random Tn phoA'-1 insertion mutagenesis, the fragment was shown to have structural genes as well as regulatory regions for nickel resistance. Southern hybridization studies showed that the nickel-resistance determinant from pEJH501 of H. alvei 5-5 was homologous to that of pTOM9 from Alcaligenes xylosoxydans 31A (AU)

Hafnia alvei 5-5, aislada en un vertedero bajo la copa del árbol hiperacumulante de níquel Sebertia acuminata (Sapoteacea) en Nueva Caledonia, resultó ser resistente a 30 mM Ni2+ y 2 mM Co2+. El plásmido de 70 kilopares de bases (kb), pEJH501 se transfirió por conjugación a Escherichia coli, Serratia marcescens y Klebsiella oxytoca. Las cepas transconjugantes expresaron resistencia inducible a entre 5 y 17 mM Ni2+, y a 2 mM Co2+. Se subclonó un fragmento Sal-EcoRI que contenía el determinante de resistencia al níquel, y el plásmido híbrido se descubrió que confería un nivel de resistencia moderado al níquel (7 mM Ni2+), incluso en E. coli. La expresión de la resistencia al níquel era inducible por exposición a concentraciones de cloruro de níquel de como mínimo 0,5 mM Ni2+. Mediante mutagénesis por inserción aleatoria de TnphoA'-1, se encontraron en el fragmento tanto genes estructurales como regiones reguladoras para la resistencia al níquel. Estudios de hibridación southern mostraron que el determinante de la resistencia al níquel del plásmido pEJH501 en H. alvei 5-5 era homólogo al de pTOM9 de Alcaligenes xylosoxydans 31A (AU)