Plasmid encoded ultraviolet-B(UV-B) resistance of bacteria isolated from pristine high altitude environments in the Argentinean Andean wetlands

FERNANDEZ ZENOFF MV; DIB JR; ORDONEZ O; MARTÍNEZ MA; FARÍAS ME

Vienna, Austria

Simposio; 11th International Symposium on Microbial Ecology; 2006

International Society for Microbial Ecology

Background and aims The effect of UV-B radiation on  survival of eleven gram positive (Bacillus, Actynomices and Staphylococcus genera) and two gram negative bacteria (g proteobacteria and Acinetobacter) isolated from wetlands located in the Puna and Andean region [Laguna Azul, 4554 m above sea level (asl) and Laguna Vilama, 4400 asl, Irradiance:10.97Wm-2 ] were investigate. High UV-B resistance were found. To determined if this resistance was related with plasmid presence, conjugation matings were performed with a sensible Bacillus subtilis rifampicin strain. Methods Methods Methods To quantify the effect of artificial UV-B (312- nm) radiation, cells in mid log phase were serial diluted in 0.9% NaCl and 100 ìl of appropriable dilution were spread onto Luria Bertani agar. Plates were irradiated with UV-B lamps. The average intensity was 0.6 Wm-2. At different times (30 and 60 minutes) plates were removed. The numbers of colony forming units (CFU) were determined. Conjugation assays were performed by standard methods, receptor strain was B. subtilis rifampicin resistant and transconjugants were exposed to artificial UV-B radiation. Results Results Results High UV-B resistance were found. An important resistance were observed in all strain with 75 to 90 % survival after 0.7 Jm-2 dose of UV-B radiation. Most organisms exhibited a high level of UV-B resistance (between 50 to 80 % of survival) after 1.4 KJm-2 dose.   All plasmid were conjugative and after plasmid incorporation, the recipient strain increased dramatically their RUV resistance. All transconjugants obtain exhibited a high level of UV-B resistance in comparison with native B. subtilis. Conclusions Conclusions Conclusions Constant exposure of Laguna Azul and Laguna Vilama to high UV-B irradiations conditions has selected strains from different species with exceptionally UV-B resistance. This resistance was codified in transferable plasmid denoting that the wide spread of these genes between the community is a common strategy for bacteria that habit extreme environments.