Ultraviolet radiation induces filamentation in bacterial assemblages from North Andean Patagonian lakes.

MODENUTTI, B.,; E. BALSEIRO, ; G. CORNO, ; C. CALLIERI, .; R. BERTONI ; E. CARAVATI

PHOTOCHEMISTRY AND PHOTOBIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2010 vol. 86 p. 871 - 881

0031-8655

Through laboratory experiments, we tested whether UV radiation(UVR) induces filamentation in natural bacteria assemblagesfrom North Andean Patagonian lakes. We incubatedwater from three different lakes for 72 h in four separatetreatments: (1) UVR + PAR (photosynthetically active radiation),(2) 50% UVR + PAR, (3) PAR and (4) 50% PAR. Theirradiance levels used in the experiments were equivalent to thoseregistered at the epilimnion of the lakes. In the UVR treatmentsfilamentation was induced after the first 24 h and the proportioncontinued to increase for the next 48–72 h. A comparison of thegross composition and diversity of the entire community (cells>0.2 lm) with bacterial filaments alone (>5.0 lm) showed thatUVR-induced filamentation is not a feature of any particularcluster. By sequencing part of the 16S rRNA gene of thetaxonomic units obtained using denaturing gels, we observed thatstrains in the b-Proteobacteria group were of relatively highimportance in filament formation, followed by Cytophaga–Flavobacterium–Bacteroides, c-Proteobacteria and a-Proteobacteria,whereas Actinobacteria were almost nonexistent in thefilaments. We propose that UVR doses equivalent to those ofAndean lakes produce bacterial morphological changes, and thatall bacterial groups except Actinobacteria can potentially formfilaments.