Response of the peanut microsymbionts to acid and metal stress.

PONSONE, L.; SOBREVALS, L.; FABRA, A.; CASTRO, S.

Villa Carlos PAz. Córdoba

Congreso; XXXVIII Reunión Nacional SAIB; 2002

SAIB

It is well known that microbes use diverse strategies, such as biotrans- formation and alteration of membrane permeability, in response to different environmental stresses. We showed that Bradyrhizobium sp SEMIA 6144 (MIRCEN, Brasil) growth rate was reduced by 50% while that glutahione (GSH) content and glutathione S-transferase activity were increased in the medium MSM at pH 5.5 and 50 J.lM AICI3. The isolate NCHA-X obtained from Córdoba soil was toler- ant at this stress condition. In order to examine the role of GSH in the response of Bradyrhizobium sp to acid stress, a GSH deficient mutant was obtained by disruption of gshA gene, encoding y- glutamylcysteine synthetase. Firstly, the GSH content was measured in the mutant strain which was very low, about 5% of the wild type level. The GSH mutant deficient growth was found significantly re- duced compared to the wild type strain growth at pH 5.5. Thus, these results suggest that GSH in Bradyrhizobium sp is involved in pro- viding protection against to low pH stress. We also evaluated in this work the efTect of the aluminium and low pH on alteration of mem- brane permeability in Bradyrhizobium sp and the isolate NCHA-X. In both peanut microsymbionts were found changes in the li- popolysaccharide content related to alteration in the cellular hydro- phobicity under stress condition. Supported by FONCYT, CONICET, SECYT/UNRC