MICROBIAL ECOLOGY METHODS FOR ASSESSING THE EFFECTS OF XENOBIOTICS IN WATER AND SOIL ECOSYSTEMS

Microbial communities are valuable indicators of the occurrence of disturbances due to exogenous physico-chemical stressors. The assessment of variations in microbial community structure is of basic importance to permit to evaluate the impact of an environmental stressor. Complex microbial communities may serve as ideal and ecologically relevant toxicity indicators. A number of microbiologically driven processes have been proposed to evaluate the effects of xenobiotics on ecosystems. Proteins, genes, metabolites, or lipids that, when expressed, present a pattern of molecular change in an organism in response to a specific environmental stressor, can be defined as environmental biomarkers. The number of techniques to study microbial communities has increased exponentially over the last 20 years and the advent of culture-independent methods, such as molecular biological techniques, has changed the view of microbial diversity. Among these techniques epifluorescence microscopy techniques, such as direct count of bacterial abundance (DAPI count) and viability (Live/Dead cell viability assay), and Fluorescence In Situ Hybridization (FISH) are very useful to study microbial communities directly from their natural environment. We report some examples of application of these techniques for evaluating the effects of some contaminants (pesticide and pharmaceuticals) to soil and water ecosystems.