ACUTE TOXICITY OF HG0 AND HG2-COLI( IONS TO ESCHERICHIA)

Acute toxicity tests using mercuric ions (Hg2+) at the concentration o f 10 and 50 mug L-1 were carried out using Escherichia coli as the org anism test. Toxicity was evaluated by measuring the inhibition in the microbial respiration, at 37-degrees-C, within 60 min after the metal spike. It has been shown that mercuric ions are reduced to the much le ss toxic form of elemental mercury (Hg0) by the glucose, which is usua lly present in the microbial culture medium as a carbon source. Based on this evidence, inhibition in the microbial respiration caused by th e presence of 5,000 mug L-1 of Hg0 were predicted to be similar to the effect caused by 10 mug L-1 of Hg2+ ions. This hypothesis has been pr oved to be true under the experimental conditions used in the bioassay s.