Functional recovery of biofilm bacterial communities after copper exposure

Potential of bacterial Communities in biofilms to recover after copper exposure was investigated. Biofilms grown outdoor in shallow water on glass dishes were exposed ill the laboratory to 0.6, 2.1, 6.8 mu mol/l copper amended surface water and a reference and subsequently to un-amended surface water. Transitions of bacterial communities were characterised with denaturing gradient gel electrophoresis (DGGE) and community-level physiological profiles (CLPP). Exposure to 6.8 mu mol/l copper provoked distinct changes in DGGE profiles of bacterial consortia, which did not reverse upon copper depuration. Exposure to 2.1 and 6.8 mu mol/l copper was found to induce marked changes ill CLPP of bacterial communities that proved to be reversible during copper depuration. Furthermore, copper exposure induced the development of copper-tolerance, which was partially lost during depuration. It is concluded that bacterial communities exposed to copper contaminated water for a period of 26 days are capable to restore their metabolic attributes after introduction of unpolluted water in aquaria for 28 days. [KEYWORDS: pollution-induced community tolerance (PICT) ; community-level physiological profiling (CLPP) ; denaturing gradient gel electrophoresis (DGGE) ; bacterial communities ; recovery]

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 in a ditch of a Dutch polder and exposed in the laboratory to copper (3 µM and a reference) at three different temperatures (10, 14 and 20 °C). 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 CLPP 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 °C increased about 3 times, whereas copper-tolerance at 20 °C 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. [KEYWORDS: Pollution-induced community tolerance (PICT) ; Community-level physiological profiling (CLPP) ; Denaturing gradient gel electrophoresis (DGGE) ; Bacterial communities ; Copper ; Temperature]

Algal–bacterial interactions in metal contaminated floodplain sediments

The aim of the present study was to investigate algal–bacterial interactions in a gradient of metal contaminated natural sediments. By means of multivariate techniques, we related the genetic structure (denaturing gradient gel electrophoresis, DGGE) and the physiological structure (community-level physiological profiling, CLPP) of the bacterial communities to the species composition of the algal communities and to the abiotic environmental variables, including metal contamination. The results revealed that genetic and physiological structure of the bacterial communities correlated with the species composition of the algal community, but hardly to the level of metal pollution. This must be interpreted as an indication for a strong and species-specific linkage of algal and bacterial species in floodplain sediments. Metals were, however, not proven to affect either the algal or the bacterial communities of the Dutch river floodplains. Algal and bacterial communities in floodplain sediments are interlinked, but are not affected by metal pollution.

Development and application of a sediment toxicity test using the benthic cladoceran Chydorus sphaericus

This study reports on the development and application of a whole sediment toxicity test using a benthic cladoceran Chydorus sphaericus, as an alternative for the use of pelagic daphnids. A C. sphaericus laboratory culture was started and its performance under control conditions was optimised. The test was firstly validated by determining dose–response relationships for aqueous cadmium and copper and ammonia, showing a sensitivity of C. sphaericus (96 h LC50 values of 594 µg Cd/L, 191 µg Cu/L and 46 mg ammonia/L at pH 8) similar to that of daphnids. Next, sediment was introduced into the test system and a series of contaminated sediments from polluted locations were tested. A significant negative correlation between survival and toxicant concentrations was observed. It is concluded that the test developed in the present study using the benthic cladoceran C. sphaericus is suitable for routine laboratory sediment toxicity testing. A test was developed for assaying sediment toxicity using a commonly occurring small-bodied cladoceran. [KEYWORDS: Chydorus ; Daphnia ; Laboratory culture ; Sediment toxicity test]