Isolation of UV-B resistant bacteria from two high altitude Andean lakes (4,400 m) with saline and non saline conditions

FLORES MARÍA R; OMAR F. ORDOÑEZ; JAVIER MALDONADO; MARÍA E. FARÍAS

JOURNAL OF GENERAL AND APPLIED MICROBIOLOGY

MICROBIOL RES FOUNDATION

Año: 2009 p. 447 - 458

0022-1260

Laguna (L.) Negra and L. Verde are high altitude Andean lakes located at 4,400 m altitude in the Andean desert (Puna) in the Argentine northwest. Both lakes are exposed to extreme weather conditions but differ in salinity contents. The aim of this work was to isolate UV-B resistant bacteria in order to determine a possible connection between resistance to UV-B and tolerance to salinity. DNA damage was determined with CPDs. Positive influence of pigmentation on UV-B resistance was also found in this work. Water samples were exposed to artificial UV-B radiation during 24 h. Isolation of bacteria was performed by plating samples on two culture media with different salinity and carbon source content. The most resistant bacteria in L. Negra were different strains of Exiguobacterium sp. and, in L. Verde, Staphylococcus sp. and Stenotrophomonas maltophilia. Both samples lakes presented CPDs significantly lower than biodosimeters.         The results showed that bacterial communities from both lakes were well adapted to high UV-B exposure under the experimental conditions, and in many cases UV-B even stimulated growth. The idea that resistance to UV-B could be related to adaptation to high salinity is still an open question that has to be answered with future experiments.