CILIATES AS BIOINDICATORS OF SOIL QUALITY: FROM BIOMARKER TO COMMUNITY STRUCTURE ANALYSIS

In recent years the potential of protozoan ciliates, as valuable bioindicators of ecosystem quality has been highlighted by a large number of authors. These eukaryotic, single-celled organisms are essential component of freshwater, marine and terrestrial ecosystems. Moreover free-living ciliates, due to their amazing molecular, cellular and physiological flexibility, have been able to colonise every type of environment up to now surveyed, from deep oceans, to polar regions and every soil types. Ciliates shown many desirable characteristics as test organisms for the design of convenient and cost effective assays, from the biomarker to the population-community level, to be used for environmental assessment. Firstly, ciliates occupy the first trophic levels and consequently represent ideal early warning indicators of ecosystem deterioration. Secondly, they play key roles in the transfer of matter and energy within the microbial loop. Moreover, numerous ciliate species can be easily cultured with a short generation time and for some species (i.e. Tetrahymena, Paramecium) genomic data and various molecular tools are available. Thus, this communication aim to describe the potential of ciliates as bioindicators of soil quality and to highlight their usefulness for the development of “prognostic” assays (i.e. able to detect sub-lethal toxicant effects of soil eluates), based on the exploitation of stress gene activation responses (biomarkers and biosensors), as well as, of “diagnostic” assays (i.e. able to detect overall ecosystem impairment), based on the analysis of the community structures of ciliates in arable soils to evaluate the potential impact of different agricultural management.