Comparison of aerobic and anaerobic [³H]leucine incorporation assays for determining pollution‐induced bacterial community tolerance in copper‐polluted, irrigated soils

Abstract

Pollution-induced community tolerance (PICT) constitutes a sensitive and ecologically relevant impact parameter in ecotoxicology. We report the development and application of a novel anaerobic [(3) H]leucine incorporation assay and its comparison with the conventional aerobic [(3) H]leucine incorporation assay for PICT detection in soil bacterial communities. Selection of bacterial communities was performed over 42 d in bulk soil microcosms (no plants) and in rice (Oryza sativa) rhizosphere soil mesocosms. The following experimental treatments were imposed using a full factorial design: two soil types, two soil water regimes, and four Cu application rates (0, 30, 120, or 280 µg g(-1)). Bacterial communities in bulk soil microcosms exhibited similar Cu tolerance patterns when assessed by aerobic and anaerobic PICT assays, whereas aerobic microorganisms tended to be more strongly selected for Cu tolerance than anaerobic microorganisms in rhizosphere soil. Despite similar levels of water-extractable Cu, bacterial Cu tolerance was significantly higher in acid sulfate soil than in alluvial soil. Copper amendment selected for significant PICT development in soils subjected to alternate wetting and drying, but not in continuously flooded soils. Our results demonstrate that soil bacterial communities subjected to alternate wetting and drying may be more affected by Cu than bacterial communities subjected to continuous flooding. We conclude that the parallel use of anaerobic and aerobic [(3) H]leucine PICT assays constitutes a valuable improvement over existing procedures for PICT detection in irrigated soils and other redox gradient environments such as sediments and wetlands.

Assessing the effects of Cu and pH on microorganisms in highly acidic vineyard soils

“…In the present study, although the largest Cu content was 272 mg kg −1 , all other soils had < 150 mg Cu kg −1 , which are moderate to small concentrations. No or only minor effects of PICT on aerobic bacteria have previously been detected at this soil Cu content (Bååth et al, 1998), even in soils freshly spiked with Cu (Díaz-Raviña et al, 1994;Aaen et al, 2011). This is also consistent with results of a field study in several vineyards from the same temperate humid zone in N.W.…”

Comparative Toxicity of Nanoparticulate CuO and ZnO to Soil Bacterial Communities

“…The sand-toxicant mixtures were mixed into the soil samples through vigorous shaking and stirring with a clean spatula to ensure homogenous application, and all treatments were run in independent duplicates. The samples were incubated for a period of 5–7 h to allow sufficient mixing and equilibration of the sample, yet sufficiently brief to ensure that the innate soil bacterial tolerance to the toxicant additions, rather than the induced tolerance following the selective growth of a tolerant community [12]–[14], [16], were assessed. After this incubation, all samples were analyzed for bacterial growth using the leucine incorporation method [19] adapted for soil [9], [20], importantly using short incubation periods (2 h).…”

“…By measuring the resulting metal concentrations in soil solution, we strengthen the connection between metals and toxicity. To provide a sensitive measure of ecotoxicity we measured the effect of the substance additions on bacterial growth using the leucine incorporation method [9], [10], previously successfully used to accurately determine toxicity of environmental toxicants including metals [11], [12], antibiotics [13]–[15], phenols [16] and salt [17].…”

Rapid and Sensitive Nitrosomonas europaea Biosensor Assay for Quantification of Bioavailable Ammonium Sensu Strictu in Soil

“…An alluvial rice paddy soil from the Mekong delta previously characterized in detail was used for in situ biosensor assays. The soil (0−15 cm depth) was air-dried (∼30 °C), sieved (2-mm mesh size), and stored at 5 °C prior to use.…”