Incidence of uvificial radiation on bacterial comunituy composition , in two andean wetlands (4.400 m)

MARÍA R. FLORES; MARÍA C. ESTEVEZ; OMAR F. ORDOÑEZ; MARÍA E. FARÍAS

Cairns, Australia

Simposio; 12th International Symposium on Microbial Ecology; 2008

ISME

Incidence of UV-B artificial radiation on bacterial community composition, in two andean wetlands (4,400 m) M.R. Flores, M.C. Estévez, O.F. Ordóñez, and M.E. Farías* * PROIMI. Av. Belgrano y Pasaje Caseros -(4000) - Tucumán, Argentina. Tel: 54-381-4344888 Fax -887  of  9:00 AM to 6:00 PM. E-mail: mefarias@proimi.org.ar, mefarias2001@yahoo.com.ar (preferid). Laguna (L.) Negra and L. Verde are wetlands located in the northwest of Argentina (4,400 meter above sea level) and exposed to high UV-B radiation and temperature changes. The aim of this work was to study the effects of UV-B radiation on bacterioplankton from these enviroments. Superficial water samples from these wetlands were exposed to artificial UV-B radiation (in vitro) during 24hs, with frecuency sampling of 1, 3, 6, 12 and 24hs.  Denaturing Gradient Gel Electrophoresis (DGGE) analisys, Cyclobutane Pyrimidine Dimers (CPDs) accumulation and bacteria isolation at different media were performed.  Bacteria isolation was done by plating in two culture media: Luria Bertani (LB) and Lagoon Media (LM). Among bacteria isolated the most resistant strains were different species of Exiguobacterium spp. from L. Negra and Staphylococcus spp. (LM) and Stenotrophomonas maltophilia (LB) from L. Verde. UV-B radiaton resistance was mainly observed in colored bateria.  DGGE analices showed the precence of band that  presented high similitude with Gamma-proteobacteria, Alpha-proteobacteria and Bacteroidetes in both wetlands.  UV-B resistance associated to a specific phylogenetic group was not detected in these environments.  CPDs accumulation was observed, the amounts increased from 0 to1280 CPD MB-1 in these wetlands after 6 hr of exposition, and it was lower than biodosimeters (of calf thymus DNA), denoting efficient UV-B resistant mechanisms.  According to the found results, it can be concluded that bacterial communities in the studied environments are well adapted to high UV-B radiation there is a relationship bewteen pigmentation and  UV-B resistance.