Bacterioplankton assemblage structure and incidence of artificial UV-B radiation on the composition of bacterial communities from four Andean wetlands (over 4,400 m) with different saline conditions

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

Rosario, Argentina.

Congreso; V Congreso Argentino de Microbiología -SAMIGE; 2008

Sociedad Argentina de Microbiología General - SAMIGE

Bacterioplankton assemblage structure and incidence of artificial UV-B radiation on the composition of bacterial communities from four Andean wetlands (over 4,400 m) with different saline conditions María R. Flores1, Omar F. Ordoñez1, María C. Estevez1, María E. Farías1 1 PROIMI - CONICET (rflores@proimi.org.ar) Bacterioplankton communities from 4 high Andean wetlands (HAW), Laguna Negra (L. Negra; 4,400 m), L. Verde (4,460 m), L. Vilama (4,600 m) and L. Chiro (4,500 m), were exposed to artificial UV radiation for 24 h. Modifications were described using denaturing gradient gel electrophoresis (DGGE), Fluorescent in situ Hybridization (FISH) and accumulation of cyclobutane pyrimidine dimers (CPDs). The 4 shallow lakes showed contrasting trophic conditions and covered a relatively wide range of limnological characteristics mainly regarding salinity. Gel analyses generated a total of 52 sequences, present in different positions. From the total of bands registered in the gels, none band were shared among the wetlands. Among these sequences the bacterial group best represented in all lakes was related to the Gamma-Proteobacteria group with 38 %, while Alpha proteobacteria represented 17 %, Beta proteobacteria 6 %, Bacteroidetes 23 % and uncultured bacteria 6 % of the bands sequenced. Interestingly, most of the sequences showed high similarity to GenBank-stored data of taxa found in halophilic habitats elsewhere in the world. These results suggest that the ubiquity of microorganisms may be probably due to their high dispersal rates, but their success in a particular habitat could be subject to environmental selection, generating bacterial assemblages well adapted to cold habitats. Little difference in DGGE profiles was detected in all four exposed wetlands. A larger band diversity was found in the more saline wetlands L. Negra and L. Vilama than in L. Verde and L. Chiro with more oligotrophic conditions. DGGE profiles of the four wetlands showed no decrease in the number of bands after UV exposure. In fact, an increase in their number was observed. CPD accumulation in all four wetlands was clearly lower than in biodosimeters and all wetlands presented almost similar damage that remained stable throughout exposure. From these results it can be concluded that bacterial communities in HAW were well adapted to high exposure of UV-B radiation, and in many cases UV-B even stimulated their growth and helped select different diversities. Environmental conditions did not seem to be connected with UV resistance since all communities assayed showed resistance regardless of salinity, oligotrophy, arsenic content, etc.