BIOREMEDIATION - Part I 

Minerva Biotecnologica 2001 March;13(1):37-9

Copyright © 2001 EDIZIONI MINERVA MEDICA

language: English

Rhizospheric bacteria promote sunflower (Helianthus annuus L.) plant growth and tolerance to heavy metals

Shilev S. I. ¹, Ruso J. ², Puig A. ⁴, Benlloch M. ³, Jorrin J. ², Sancho E. ¹

¹ Department of Microbiology, ETSIAM, Universidad de Córdoba, Cordoba, Spain; 2Department of Biochemistry and Molecular Biology, ETSIAM, Universidad de Córdoba, Cordoba, Spain; ³ Department of Agronomy, ETSIAM, Universidad de Córdoba, Cordoba, Spain; ⁴ Department of Microbiology, Centro de Investigación y Formación Agrária, Cordoba, Spain, EMIR-UCO (Multidisciplinary Research Project on Phytoremediation), Agronomy and Forest Science High Technical School, University of Córdoba, Córdoba, Spain

Background. It is ­known ­that rhiz­os­pher­ic micror­gan­isms ­increase tol­er­ance to bio­tic and abi­ot­ic stress­es, in gen­er­al, and to ­heavy met­als, in par­tic­u­lar. As ­part of mul­ti­dis­ci­pli­nary ­research pro­ject on phy­tor­e­me­di­a­tion, car­ried out at the ­EMIR-UCO ­group, involve­ment of rhiz­os­pher­ic bac­te­ria on ­plant tol­er­ance to tox­ic met­als has ­been eval­u­at­ed.
Methods. Different bac­te­ria pop­u­la­tions ­have ­been ­obtained ­from ­roots and sur­round­ing ­soil in a met­al con­tam­i­nat­ed ­area (Aznalcóllar, Southern Spain). These pop­u­la­tions ­have ­been char­ac­ter­ized ­with ­respect to ­their tol­er­ance to ­heavy met­als (As, Pb, Cd, Zn, and Cu). Six, out of the 60 pop­u­la­tions eval­u­at­ed, ­have ­been select­ed ­because ­of their abil­ity to tol­er­ate the max­i­mum dos­es test­ed. Tolerance was gen­er­al and not selec­tive to spe­cif­ic met­als. By ­using sun­flow­er as experi­men­tal mod­el ­system in green­house experi­ments, the ­effects of the met­al tol­er­ant bac­te­ria pop­u­la­tions on ­plant ­growth, ­plant tol­er­ance and ­heavy met­als accu­mu­la­tion ­have ­been eval­u­at­ed.
Results. Higher ­growth and bio­mass devel­op­ment ­were ­obtained ­when the select­ed bac­te­ria ­were add­ed to the ­soil. At the high­est met­al dos­es, a reduc­tion in chlo­ro­phyll con­tent was occa­sion­al­ly ­observed, ­being ­these symp­toms clear­ly man­i­fest­ed in treat­ments ­with addi­tion of select­ed bac­te­ria. With ­respect to ­heavy met­als accu­mu­la­tion, an ­increase in met­al ­uptake and/or trans­lo­ca­tion to the aer­i­al ­part of the ­plants was meas­ured, ­being ­this clear­ly affect­ed in the ­case of the addi­tion of Zn, in the pres­ence of select­ed bac­te­ria.
Conclusions. Work in ­progress, is now ­focused in the iden­tifi­ca­tion of the dif­fer­ent bac­te­ria pop­u­la­tions, and the elu­ci­da­tion of mech­a­nisms ­involved in the ­increased tol­er­ance of met­als in ­plants in the pres­ence of ­mixed select­ed pop­u­la­tions.