Cadmium Accumulation and Tolerance in Bradyrhizobium spp. (Peanut Microsymbionts)

ELIANA BIANUCCI ADRIANA FABRA STELLA CASTRO

CURRENT MICROBIOLOGY

SPRINGER

Lugar: New York; Año: 2011 vol. 62 p. 96 - 100

0343-8651

In this study, the effect of cadmium (Cd) on cell viability and its accumulation in Bradyrhizobium spp. (peanut microsymbionts) as well as the role of glutathione (GSH) in the tolerance to this metal were investigated. A reference strain recommended as peanut inoculant (Bradyrhizobium sp. SEMIA6144) grew up to 10 muM Cd meanwhile a GSH-deficient mutant strain (Bradyrhizobium sp. SEMIA6144-S7Z) was unable to grow at this concentration. Two native peanut isolates obtained from Córdoba soils (Bradyrhizobium sp. NLH25 and Bradyrhizobium sp. NOD31) tolerated up to 30 muM Cd. The analysis of Cd content showed that Bradyrhizobium sp. SEMIA6144 accumulated a high amount of this metal, but a considerable inhibition of growth was observed compared to tolerant strains at 10 muM Cd. At this concentration, the intracellular GSH content of all the Bradyrhizobium sp. strains was not modified in comparison to control conditions. However, at 30 muM Cd, the intracellular GSH content significantly increased in Bradyrhizobium sp. strains NLH25 and NOD31. Thus, the distinct response of each Bradyrhizobium sp. strain to Cd reveals that, even in closely related lineages, there are strain-specific variations influencing the levels of tolerance to this metal. Indeed, the native peanut isolates tolerated higher Cd concentration than the reference strain, possibly due to an increase in GSH levels which could act as a detoxifying agent.