In vitro toxicity testing using marine luminescent bacteria (Photobacterium phosphoreum): the Biotox test

By Kahru, A.

Marine luminescent bacteria emit light naturally when they are in an optimal environment. If harmful substances are present, their bioluminescence decreases, and the amount of light loss is proportional to the toxicity. In this paper, a new short-term toxicity test system, Biotox, based on freeze-dried Photobacterium phosphoreum, is assessed. Concentration-effect curves for 25 laboratory chemicals were measured, and EC50 values (the concentrations of chemical, micrograms/ml, which reduce the light output of bacteria by 50% after being in contact with bacteria over a certain time period) were calculated. The sensitivity of the Biotox test to hydrophilic compounds was approximately two times greater than the sensitivity of the Microtox test. However, the sensitivity of the Biotox test to hydrophobic compounds was shown to be 2-4 times lower than the sensitivity of the Microtox test. The Biotox test was especially sensitive to As(5+), giving an EC50 value of 0.04 micrograms/ml, compared with 1.5 micrograms/ml in the Microtox assay.