INVESTIGADORES
DRAGHI Walter Omar
artículos
Título:
Conjugal transfer of a Sinorhizobium meliloti cryptic plasmid evaluated during a field release and in soil microcosms
Autor/es:
GIUSTI M. A.; LOZANO, M.J.; TORRES TEJERIZO, G.A.; MARTINI, C.; SALAS, M.E.; LÓPEZ, J.L.; DRAGHI, W.O.; DEL PAPA, M.F.; PISTORIO, M.; LAGARES, A.
Revista:
EUROPEAN JOURNAL OF SOIL BIOLOGY
Editorial:
ELSEVIER FRANCE-EDITIONS SCIENTIFIQUES MEDICALES ELSEVIER
Referencias:
Lugar: Paris; Año: 2013 vol. 55 p. 9 - 12
ISSN:
1164-5563
Resumen:
Horizontal gene transfer (HGT) is a central evolutionary mechanism that
mediates the diversification and adaptation of bacteria in general and
of rhizobia in particular. The few quantitative data on the conjugal
transfer of rhizobial plasmids in soil correspond to the pSym (symbiotic
genes-carrying replicons), with no information available regarding
transfer frequencies in soil of other (namely accessory/cryptic)
plasmids that are present in several rhizobial species. Thus, we
examined here the conjugal transfer in non-sterile soil of the model Sinorhizobium meliloti
cryptic plasmid pSmeLPU88b. Under field conditions the proportion of
nodules containing indigenous rhizobia that acquired the plasmid
pSmeLPU88b and then nodulated the trapping plants could be estimated as
<0.1% (transconjugants/nodule) over an 18-month sampling period that
followed inoculation. The collected evidence showed that the release of
rhizobia by means of standard seed-inoculation procedures did not result
in a massive transfer of the introduced cryptic plasmid pSmeLPU88b to
the indigenous bacteria that nodulate trapping alfalfa plants. Using a
laboratory microcosm system performed with the same soil from the
experimental field, we demonstrated that transconjugants were generated
in the rhizosphere at a frequency of ca. 1.43 × 10−6 transconjugants/recipient, a frequency from 102 to 103
times lower than that corresponding to the transfer of the same plasmid
in rich-medium agar plates. The estimation of mobilization frequencies
of rhizobial plasmids in soil is a necessary step toward the development
of quantitative predictive models of gene-dispersal frequencies from
inoculated strains to other rhizobia and soil bacteria.