CONICET | Buscador de Institutos y Recursos Humanos

High Altitude Andean Wetlands (HAAW) are a group of shallow lakes and salterns located above 4400 masl, exposed to high UV radiation, high salinity and elevated heavy metals content. These ecosystems emerged as an amazing source of biological strategies developed by microorganisms to survive under extreme conditions. The UV-resistant Acinetobacter sp.Ver3 isolated from HAAW displays catalase activitylevels up to 15 times higher than control strains (Di Capuaet. al., 2011). After genome pyrosequencing and gene annotation, two related ORFsencoding catalase activity were identified:katAandkatB. Our results show that the katA product accounts for most of the catalase activity observed,being localized in cytosol. On the other side,katB encodes a protein carrying a signal targeting peptide responsible not only for periplasmic emplacement but also for correct folding and enzyme activity. Experiments inE. Colisecretion deficient strains, including heterologous expression and subsequent periplasm isolation, revealed that KatB is delivered by the TAT system. We constructed a kat-insertional mutantof Acinetobacter baylyi ADP1 highly sensitive to peroxide and UV. When transformed with a plasmid carrying the full katA gene the wild-type phenotype was restored, suggesting this protein plays a main role in the tolerance to such pro-oxidant agents.When Ver3 cells were challenged with peroxide an increase of KatB was observed by inmunostaining and, in lesser extent, also of KatA. When cultures were exposed to UV, only the rise of KatB was distinguishable. Our results indicate that polyextremophile Acinetobacter sp.Ver3 takes advantage of both a cytosolic, highly active catalase, and an inducible periplasmic enzyme as efficient antioxidant barrier.