UV-resistant Acinetobacter sp. isolates from Andean wetlands display high catalase activity.

Andean wetlands are characterized by their extreme environmental conditions such as high UV radiation, elevated heavy metal content and salinity. We present here the first study on UV tolerance and antioxidant defense of four Acinetobacter strains: Ver3, Ver5 and Ver7, isolated from Lake Verde, and N40 from Lake Negra, both lakes located 4400 m above sea level. All four isolates displayed higher UV resistance compared with collection strains, with Ver3 and Ver7 being the most tolerant strains not only to UV radiation but also to hydrogen peroxide (H(2)O(2)) and methyl viologen (MV) challenges. A single superoxide dismutase band with similar activity was detected in all studied strains, whereas different electrophoretic pattern and activity levels were observed for catalase. Ver3 and Ver7 displayed 5-15 times higher catalase activity levels than the control strains. Analysis of the response of antioxidant enzymes to UV and oxidative challenges revealed a significant increase in Ver7 catalase activity after H(2)O(2) and MV exposure. Incubation of Ver7 cultures with a catalase inhibitor resulted in a significant decrease of tolerance against UV radiation. We conclude that the high catalase activity displayed by Ver7 isolate could play an important role in UV tolerance.