Heavy metal toxicity to bacteria – Are the existing growth media accurate enough to determine heavy metal toxicity?

• Published in: Chemosphere (Oxford) Vol. 90; no. 3; pp. 1195 - 1200
• Main Authors: Rathnayake, I.V.N., Megharaj, Mallavarapu, Krishnamurti, G.S.R., Bolan, Nanthi S., Naidu, Ravi
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-01-2013; Elsevier
• Subjects: Action of physical and chemical agents on bacteria; Bacillus - cytology; Bacillus - drug effects; Bacteria; Bacteriology; Bioavailability; Biological and medical sciences; Cadmium; Cadmium - toxicity; Copper; Copper - toxicity; Culture Media - toxicity; Fundamental and applied biological sciences. Psychology; Heavy metal toxicity; Ion-Selective Electrodes; Microbiology; Speciation; Cadmium; Bacteria; Bioavailability; Copper; Heavy metal toxicity; Speciation; Culture medium; Chemical analysis; Pollutant behavior; Toxicity; Bacillus thuringiensis; Transition metal; Bacillaceae; Heavy metal; Bacillales; Bacillus megaterium
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2012.09.036

► A new bacterial growth medium containing low levels of metal-chelates was formulated. ► This medium has high free metal ion activity and more suitable to determine metal toxicity. ► This medium provides a viable option for the study of metals–bacteria interactions.
A new minimal medium was formulated considering the limitations of the existing media for testing heavy metal sensitivity to bacteria. Toxicity of cadmium and copper to three bacteria was investigated in the new medium and compared with three other media commonly used to study the effect of the toxic metals. Based on speciation data arrived at using ion-selective electrodes, the available free-metal concentration in solution was highest in the MES-buffered medium. This finding was strongly supported by the estimated EC50 values for the metals tested based on the toxicity bioassays. The free-ionic cadmium and copper concentrations in the medium provide more accurate determination of metal concentrations that affects the bacteria, than with most of other existing media. This will avoid doubts on other media and misleading conclusions relevant to the toxicity of heavy metals to bacteria and provides a better option for the study of metal–bacteria interactions.