title: A flow cytometry based oligotrophic pollutant exposure test to detect bacterial growth inhibition and cell injury.
abstract: Toxicity of chemical pollutants in aquatic environments is often addressed by assays that inquire reproductive inhibition of test microorganisms, such as algae or bacteria. Those tests, however, assess growth of populations as a whole via macroscopic methods such as culture turbidity or colony-forming units. Here we use flow cytometry to interrogate the fate of individual cells in low-density populations of the bacterium Pseudomonas fluorescens SV3 exposed or not under oligotrophic conditions to a number of common pollutants, some of which derive from oil contamination. Cells were stained at regular time intervals during the exposure assay with fluorescent dyes that detect membrane injury (i.e., live-dead assay). Reduction of population growth rates was observed upon toxicant insult and depended on the type of toxicant. Modeling and cell staining indicate that population growth rate decrease is a combined effect of an increased number of injured cells that may or may not multiply, and live cells dividing at normal growth rates. The oligotrophic assay concept presented here could be a useful complement for existing biomarker assays in compliance with new regulations on chemical effect studies or, more specifically, for judging recovery after exposure to fluctuating toxicant conditions.
authors.affiliation: Department of Fundamental Microbiology, University of Lausanne, Bâtiment Biophore, Quartier UNIL-Sorge, 1015 Lausanne, Switzerland.
authors.forename: Kamila
authors.initials: K
authors.lastname: Czechowska
authors.forename: Jan Roelof
authors.initials: JR
authors.lastname: van der Meer
mesh_terms: D000473:Alkanes / Q000633:toxicity; D000704:Analysis of Variance; D001713:Biphenyl Compounds / Q000633:toxicity; D002733:Chlorophenols / Q000633:toxicity; D004996:Ethidium / Q000633:toxicity; D005434:Flow Cytometry / Q000379:methods*; D005453:Fluorescence; D008954:Models, Biological; D009281:Naphthalenes / Q000633:toxicity; D011551:Pseudomonas fluorescens / Q000187:drug effects* / Q000254:growth & development*; D018675:Toxicity Tests / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D000473:Alkanes; D001713:Biphenyl Compounds; D002733:Chlorophenols; D009281:Naphthalenes; D014874:Water Pollutants, Chemical; C024713:n-tetradecane; C031721:naphthalene; C055142:2-chlorobiphenyl; C029107:4-chlorophenol; D004996:Ethidium