Effects of copper and temperature on aquatic bacterial communities

The present study aimed to characterise effects of copper and temperature on bacterial communities in photosynthetic biofilms using a suit of supplementary methods: pollution-induced community tolerance (PICT), DNA profiles with denaturing gradient gel electrophoresis (DGGE) and physiological profiles with community-level physiological profiling (CLPP). Biofilms of algae and bacteria were grown a ditch of a Dutch polder and exposed in the laboratory to copper (3 muM and a reference) at three different temperature's: (10, 14 and 20degreesC). Bacterial communities sampled from the field showed heterogeneity in their physiological profiles, however the-heterogeneity decreased during laboratory incubation. After 3 days laboratory incubation, the copper treated biofilms were different from the reference biofilms, as revealed by DGGE and CUP analyses. Effects of temperature were not observed in the CLPPs, or in the DGGE profiles. PICT was observed for the bacterial communities at all temperatures. The copper-tolerance at 10 and 14 degreesC increased about 3 times, whereas copper-tolerance at 20degreesC increased about 6 times. Temperature had an effect on the community tolerance, but not on the structure or on the physiological profile, suggesting that temperature was not a major factor causing successional changes under these laboratory conditions. In contrast, temperature had an effect on tolerance development indicating that the exposure to copper was enhanced at higher temperature. (C) 2004 Elsevier B.V. All rights reserved.