Pollution effects on soil microorganisms
We have pioneered the use of growth based techniques to measure Pollution Induced Community Tolerance (PICT) for bacteria in soil to study effects of heavy metals and organic pollutants including phenols and antibiotics. We have contrasted different methods to estimate PICT in soil and shown that growth based endpoints are of superior efficiency and sensitivity. PICT has also been used to directly study the often elusive concept of co-tolerance.
We are now using the PICT concept in co-operation with the University of Copenhagen (Kristian Koefoed Brandt and joint postdoc David Fernandez Calvino) in a project with the aim to use the PICT concept in risk assessments of antibiotics and biocides (PICT-RISK: Evaluation of pollution-induced community tolerance (PICT) as an ecologically relevant effect and exposure indicator for RISK assessment of biocides). In collaboration with Olof Berglund and Hans Bockgård, CEC, we are using the PICT concept to determine the mode of action for the environmental toxicity of silver nano-particles (AgNP). A new application of the PICT concept recently also includes the elucidation of the microbial responses to soil salinization.
An important aspect in ecotoxicology is to quantify effects of pollutants in different environments. Most ecotoxicological tests in soil that rely on community or flux studies and not single organisms are problematic. First, they can be affected by most other environmental factors such as nutrient conditions. This will be especially problematic when very different soils are studied or when organic pollutants, that can be metabolized and thus be a nutrient source for the microorganisms, are studied. Second, they can not be used to detect which pollutant that is the most toxic in a multiple pollution situation, a situation which very often is the case in nature. One way of circumventing these problems are to use the microorganisms themselves as indicator of their environment, since the level of tolerance of the community will increase if a toxic substance is applied, and thus the degree of tolerance can be seen as a measure of the level of toxicity. This is the theoretical basis behind the concept of Pollution Induced Community Tolerance (PICT).