Importance of glutathione in growth of peanut rhizobia under cadmium exposure

BIANUCCI, E., IBAÑEZ, F., FABRA, A., CASTRO, S.

Mar del Plata, Buenos Aires

Congreso; XLIII Reunion Anual Sociedad Argentina de Investigacion en Bioquimica y Biologia Molecular; 2007

SAIB

Glutathione (GSH) is one of the best known non-enzymatic defense systems. We demonstrated that GSH plays a crucial role in the defense of Bradyrhizobium sp. SEMIA 6144 against different environmental stresses. For that, a GSH-deficient mutant (Bradyrhizobium sp. 6144-S7Z) was obtained by disruption of gshA gene which encodes the enzyme glutamylcysteine synthetase. Taking into account that cadmium (Cd) is a toxic heavy metal that induces oxidative stress in microorganisms, our objective was to investigate the effect of this metal on the growth and survival of B. sp recommended as inoculants to peanut as well as the role of GSH in the strategy of tolerance to Cd. The wild-type and GSH-deficient mutant of B. sp. SEMIA6144 and B. sp. C-145 strains were grown at different concentrations of Cd (0-15 µM) in the YEM medium. B. sp. SEMIA6144 grew up to 15 µM Cd without difference in the GSH content respect to control meanwhile the mutant strain was unable to grow at 15 µM Cd. B. sp. C-145 showed a 75% of decrease of growth with an increase in the GSH content at 15 ìM Cd. This result could suggest that the GSH content was not enough to avoid the deleterious effect of Cd on the growth of B. sp. C-145. In conclusion, our findings show that the strains used as field peanut inoculants differ in the tolerance to Cd being B. sp. SEMIA 6144 tolerant and B. sp. C-145 sensitive.