Extremophile Culture Collection from Andean Lakes: Extreme Pristine Environments that Host a Wide Diversity of Microorganisms with Tolerance to UV Radiation

OMAR F. ORDOÑEZ; MARIA R. FLORES; JULIAN R. DIB; AGUSTIN PAZ; MARIA E. FARIAS

MICROBIAL ECOLOGY

Springer

Lugar: New York ; Año: 2009

0095-3628

Abstract A total of 88 bacterial strains were isolated from 6 Andean lakes situated at altitudes ranging from 3,400 to 4,600m above sea level (asl): L. Aparejos (4,200 m), L. Negra (4,400 m), L. Verde (4,460 m), L. Azul (4,400), L. Vilama (4,600 m) and Salina Grande (3,400 m). Salinity ranged from 0.4 to 117 ppm. General diversity was determined by DGGE analysis. From the DGGE bands excised 182 bacterial sequences of good quality were obtained. Gamma proteobacteria and Cytophaga/Flavobacterium/Bacteroides (CFB) were the most abundant phylogenetic groups with 42 and 18% of identified bands, respectively. The isolated strains were identified by sequence analysis. Isolated bacteria were subjected to four different UV-B exposure times: 0.5, 3, 6, 12 and 24h. Afterwards, growth of each isolate was monitored, and resistance was classified according to the growth pattern. A wide interspecific variation among the 88 isolates was observed. Medium and highly resistant strains accounted for 43.2 % and 28.4 % of the isolates, respectively, and only 28.4 % was sensitive. Resistance to solar radiation was equally distributed among the isolates from the different lakes regardless of the salinity of the lakes and isolate pigmentation. 44.5 % of the highly resistant isolates belonged to gamma proteobacteria, 33.3% to beta proteobacteria, 40% belonged to alpha proteobacteria, 50% to CFB and among Gram-positive 33.3 % of the organisms were HGC and 44.5 % Firmicutes. Most resistant strains belonged to genera like Exiguobaceterium sp., Acinetobacter sp., Bacillus sp., Micrococcus sp., Pseudomonas sp., Sphyngomonas sp., Staphylococcus sp. and Stenotrophomonas sp. The current study provides further evidence that gamma proteobacteria are the most abundant and the most UV-B resistant phylogenetic group in Andean lakes and that UV resistance in bacteria isolated from these environments do not depend on pigmentation and tolerance to salinity.