The effect of an acute copper exposure on the diversity of a microbial community in North Sea sediments as revealed by DGGE analysis--the importance of the protocol.

The aim of the work was to investigate whether the marine bacterial communities in a North Sea sediment with background metal concentrations were affected by an acute copper exposure and if a commonly used molecular technique, denaturing gradient gel electrophoresis (DGGE), was robust enough to investigate the community changes. Sediments (n = 6) were placed in small microcosms and spiked with copper (50 microg/l). Controls were left untreated. After 12 days, bioavailable copper increased up to a factor 2.5 in the sediments. Plate counts and chitinase activity measurements have suggested limited effects of copper on growth rate and cell metabolism. To test the robustness of DGGE three different protocols were used. The three protocols lead to different conclusions. As a whole, it seems that copper had no immediate effect on the genetic diversity of the community. However, copper-sensitive bacterial populations were detected by one of the DGGE protocols. It is concluded that the DGGE approach is a valuable tool to investigate the effect of pollutants on microbial communities only if various DGGE protocols are compared.