title: Occurrence of copper resistant mutants in the toxic cyanobacteria Microcystis aeruginosa: characterisation and future implications in the use of copper sulphate as algaecide.
abstract: Freshwater toxic cyanobacteria are an increasing problem to human and animal health. Control of cyanobacteria in water supply reservoirs involves the use of algaecides, such as copper sulphate, usually in a repetitive way. Repercussions of recurrent algaecide treatments on cyanobacteria population dynamics remain still unknown. We studied the adaptation of cyanobacteria to lethal doses of copper sulphate by using Microcystis aeruginosa as an experimental model. A fluctuation analysis demonstrated that copper-resistant cells arise by spontaneous mutations that occur randomly prior to exposition to copper sulphate. The rate of spontaneous mutation from copper sensitivity to resistance was 1.76 x 10(-6) mutants per cell division. Resistant mutants exhibited a diminished fitness in the absence of copper sulphate, but only these variants were able to grow at Cu(2+) concentrations higher than 5.8 microM. In addition, copper-resistant cells were significantly smaller than wild-type ones. Warnings on the long-term consequences of repetitive algaecide treatments in water supplies are suggested.
authors.affiliation: Dpto. Producción Animal (Genética), Facultad de Veterinaria, Universidad Complutense de Madrid, Avenida Puerta de Hierro s/n, Madrid E-28040, Spain.
authors.forename: Libertad
authors.initials: L
authors.lastname: García-Villada
authors.forename: Marcos
authors.initials: M
authors.lastname: Rico
authors.forename: M María
authors.initials: MM
authors.lastname: Altamirano
authors.forename: Laura
authors.initials: L
authors.lastname: Sánchez-Martín
authors.forename: Victoria
authors.initials: V
authors.lastname: López-Rodas
authors.forename: Eduardo
authors.initials: E
authors.lastname: Costas
mesh_terms: D001427:Bacterial Toxins / Q000737:chemistry*; D003300:Copper / Q000737:chemistry / Q000494:pharmacology*; D019327:Copper Sulfate / Q000737:chemistry / Q000494:pharmacology*; D004352:Drug Resistance, Microbial; D056890:Eukaryota / Q000187:drug effects / Q000254:growth & development*; D046931:Microcystis / Q000187:drug effects / Q000254:growth & development*; D009154:Mutation; D014871:Water Microbiology; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
chemical_list: D001427:Bacterial Toxins; D003300:Copper; D019327:Copper Sulfate