Evaluation of the toxicity of several heavy metals by a fluorescent bacterial bioassay.
This new bioassay determined the toxicity of chemical compounds dissolved in water by measuring the degree of inhibition of the ultraviolet light-stimulated fluorescence of Escherichia coli in a culture medium in which 4-methylumbelliferyl beta-D-glucuronide was the only carbon source. Inhibition produced by one of five heavy-metal salts (Cd2+, Cr6+, Hg2+, Pb2+ or Zn2+) was the end-point and comparison standard to determine the EC50 and minimum effective concentration (MEC) that produced a decrease of E. coli growth rate, increased doubling time and percentage inhibition and reduced numbers of generations; all these values were derived from the fluorescence signals. Only Cr6+ and Hg2+ at two concentrations (0.25 and 0.5 mg l-1) almost completely inhibited this E. coli strain. All toxicant concentrations tested produced at least partial inhibitions of growth; Cr6+, Hg2+ and Cd2+, in that order, were most toxic, and Pb2+ the least. Zn2+ gave higher EC50 values at 3 h of incubation than at 4 h. The method was simple, rapid and inexpensive and would permit a large number of samples to be tested quickly.
Mariscal
A
A
Departament of Medecine Preventive and Public Health, School of Medecine, University of Malaga, Spain.
García
A
A
Carnero
M
M
Gómez
J
J
Pinedo
A
A
Fernández-Crehuet
J
J
D001681:Biological Assay / Q000379:methods*; D002104:Cadmium / Q000633:toxicity; D002857:Chromium / Q000633:toxicity; D004926:Escherichia coli / Q000187:drug effects* / Q000254:growth & development; D005453:Fluorescence; D007854:Lead / Q000633:toxicity; D008628:Mercury / Q000633:toxicity; D008670:Metals / Q000633:toxicity*; D018675:Toxicity Tests / Q000379:methods*; D014466:Ultraviolet Rays; D015032:Zinc / Q000633:toxicity
D008670:Metals; D002104:Cadmium; D002857:Chromium; D007854:Lead; D008628:Mercury; D015032:Zinc