Characterization of the antioxidant response of Exiguobacterium sp. isolated from high altitude Andean wetlands

OMAR ORDOÑEZ; CECILIA DI CAPUA; NESTOR CORTEZ; FARIAS MARIA EUGENIA

Tucuman

Congreso; VII CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL SAMIGE DEL BICENTENARIO; 2011

Sociedad Argentina de microbiologia

The Andean wetlands, placed at 4000 m over the sea level have specific characteristics as high UV radiation, high salinity and heavy metals concentrations. In this work we studied the antioxidant response of two bacteria isolated from these wetlands measuring the activity of the detoxifying enzymes catalase and superoxide dismutase (SOD). The strains Exiguobacterium sp., N30 and S17 isolated from Lake Negra and Socompa, respectively were subjected to the oxidative agents methyl viologen (MV) and hydrogen peroxide (H2O2). After the challenge, bacteria survival and enzymatic activity were measured and results were compared with those obtained with the strain from the German collection Exiguobacterium sp DSM6208. The high altitude isolations N30 and S17 showed higher survival percentages than Exiguobacterium sp DSM6208 when subjected to MV, while no significant differences were found when H2O2 was used as oxidative agent. The enzymatic activities of SOD and catalase were visualized by non denaturizing polyacrilamide electrophoresis using bacteria crude extracts. Also, the actions of different enzymatic inhibitors (potassium cyanide and H2O2) for SOD activity were studied. One band corresponding to SOD activity was observed for the three strains analyzed and no inhibition was observed with the agents used indicating that the metal cofactor could be Mn or the enzyme belongs to the cambialistic group. On the opposite, for catalase a more complex electophoretic patron was found between the strains studied. Exiguobacterium sp. DSM6208 showed three bands with catalase activity while for N30 and S17 two and one band was detected, respectively. However, the activity levels revealed by electrophoresis were similar for all the Exiguobacterium strains studied. These results showed that the Exiguobacterium isolated from the Andean wetlands have a higher resistance to oxidative stress which could be explained by the differences between the catalases found for the assayed strains, observed as distinct band mobility in the gels.