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Appl. Environ. Microbiol. doi:10.1128/AEM.01333-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Diverse Responses to UV-B Radiation and Repair Mechanisms of Bacteria Isolated from High Altitude Aquatic Environments (3,600 - 4,560 m)

Planta Piloto de Procesos Industriales Microbiológicos (PROIMI), Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Av. Belgrano y Pje. Caseros -(4000) - Tucumán, Argentina

^* To whom correspondence should be addressed. Email: mefarias{at}proimi.org.ar.

	Abstract

Acinetobacter johnsonii A2 isolated from the natural community of Laguna Azul (Andean Mountains at 4,560 m above sea level), Serratia marcescens MF42, Pseudomonas sp. MF8 isolated from the planktonic community and Cytophaga sp. MF7 from the benthic community from Laguna Pozuelos (Andean Puna at 3,600 m above sea level) were subject to extreme UV-B (3,931 J m^-2) irradiation. In addition, a marine Pseudomonas putida 2IDINH and a second Acinetobacter johnsonii ATCC 17909 were used as external controls. Resistance to UV-B, kinetic rates of light dependent (UV-A (315-400 nm) and cool white light (400-700 nm)) and independent reactivation following exposure, were determined by measuring survival (expressed as colony forming units (CFU)) and accumulation of cyclobutane pyrimidine dimers (CPD). Significant differences in survival after UV-B irradiation were observed: Acinetobacter johnsonii A2 (48%), Acinetobacter johnsonii ATCC 17909 (20%), Pseudomonas sp. MF8 (40%), marine Pseudomonas putida 2IDINH (12%), Cytophaga sp. MF7 (20%) and Serratia marcescens (21%). Most bacteria exhibited little DNA damage (between 40 to 80 CPD/MB) except for the benthic isolate Cytophaga sp. MF7 (400 CPD/Mb) and Acinetobacter johnsonii ATCC 17909 (160 CPD/Mb). The recovery strategies through dark and light repair were different in all strains. The most efficient in recovering were both Acinetobacter johnsonii and Cytophaga sp. MF7; Serratia marcescens MF42 showed intermediated recovery and in both Pseudomonas recoveries was essentially zero. The UV-B response and recovery ability of the different bacteria were consistent with the irradiation levels in their native environment.

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