title: Microcalorimetry: a powerful and original tool for tracking the toxicity of a xenobiotic on Tetrahymena pyriformis.
abstract: Fighting against water pollution requires the ability to evaluate the toxicity of pollutants such as herbicides. Tetrahymena pyriformis are ubiquitous ciliated protozoans commonly used in ecotoxicological research. Microcalorimetry can be used in many biological investigations as a universal, non-destructive and highly sensitive tool that provides a continuous real-time monitoring of the metabolic activity. This technique based on the thermal power output was applied to evaluate the influence of herbicide diuron on cultures of T. pyriformis. The heat flux produced upon addition of 0, 3.5, 7.0, 14.0, 28.0, and 56.0 µg mL⁻¹ of diuron was monitored. The biomass change during the growth was also determined by flow cytometry. The results confirmed that the growth of T. pyriformis is progressively inhibited as the concentration of diuron increases and revealed that the state of the living system is severely altered at a concentration of 56.0 µg mL⁻¹. The IC₅₀ was estimated at 13.8 µg mL⁻¹ by microcalorimetry and at 18.6 µg mL⁻¹ by flow cytometry. It was shown that microcalorimetry is not only a very effective tool for the determination of the growth rate constant but that it is also a valuable probe for a rapid detection of the metabolic perturbations and, in ultimate cases, of the critical alterations of the living system under the action of a toxic agent.
authors.affiliation: Clermont Université, Université Blaise Pascal, Laboratoire "Microorganismes : Génome et Environnement", BP10448, F-63000 Clermont-Ferrand, France; CNRS, UMR6023, LMGE BP80026, F-63171 Aubière, France. Electronic address: genevieve.bricheux@univ-bpclermont.fr.
authors.forename: Geneviève
authors.initials: G
authors.lastname: Bricheux
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Bonnet
authors.forename: Jacques
authors.initials: J
authors.lastname: Bohatier
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Morel
authors.forename: Nicole
authors.initials: N
authors.lastname: Morel-Desrosiers
mesh_terms: D002151:Calorimetry / Q000379:methods*; D004237:Diuron / Q000633:toxicity*; D006540:Herbicides / Q000633:toxicity*; D020128:Inhibitory Concentration 50; D013769:Tetrahymena pyriformis / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D018675:Toxicity Tests / Q000379:methods*; D015262:Xenobiotics / Q000633:toxicity*
chemical_list: D006540:Herbicides; D015262:Xenobiotics; D004237:Diuron
keywords: Cytometry; Diuron; Microcalorimetry; Tetrahymena pyriformis