title: New methodological improvements in the Microtox® solid phase assay.
abstract: The classic Microtox® solid phase assay (MSPA) based on the inhibition of light production of the marine bacteria recently renamed Aliivibrio fischeri suffers from various bias and interferences, mainly due to physico-chemical characteristics of the tested solid phase. To precisely assess ecotoxicity of sediments, we have developed an alternative method, named Microtox® leachate phase assay (MLPA), in order to measure the action of dissolved pollutants in the aqueous phase. Two hypotheses were formulated to explain the observed difference between MSPA and MLPA results: a real ecotoxicity of the solid phase or the fixation of bacteria to fine particles and/or organic matter. To estimate the latter, flow cytometry analyses were performed with two fluorochromes (known for their ability to stain bacterial DNA), allowing correction of MSPA measurements and generation of new (corrected) IC50. Comparison of results of MLPA with the new IC50 MSPA allows differentiating real ecotoxic and fixation effect in classic MSPA especially for samples with high amount of fines and/or organic matter.
authors.affiliation: Laboratoire des Interactions Ecotoxicologie, Biodiversité, Ecosystèmes, Université Paul Verlaine-Metz, UMR CNRS 7146, Campus Bridoux, Batiment IBISE, Rue Delestraint, 57070 Metz, France. karenburga@yahoo.com
authors.forename: Karen F
authors.initials: KF
authors.lastname: Burga Pérez
authors.forename: Rayna
authors.initials: R
authors.lastname: Charlatchka
authors.forename: Leila
authors.initials: L
authors.lastname: Sahli
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Férard
mesh_terms: D048908:Aliivibrio fischeri / Q000187:drug effects*; D005434:Flow Cytometry; D005456:Fluorescent Dyes / Q000032:analysis / Q000737:chemistry; D019015:Geologic Sediments / Q000032:analysis*; D020128:Inhibitory Concentration 50; D018675:Toxicity Tests / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity*
chemical_list: D005456:Fluorescent Dyes; D014874:Water Pollutants, Chemical