Abstract
Analytical conditions for evaluating the chemical toxicity were examined using luminescent bacterium Vibrio fischeri (V. fischeri) deutsche sammluing von microorganismen (DSM) 7151, taking the medium composition into consideration. The manipulation of the cells for optimal assay was obtained as follows; the cells were grown in luminescence (LM) medium containing 3 g/l of glycerol for 18 hr. They were washed twice with artificial seawater (ASW) and then diluted about 128 folds by ASW, corresponding to 1.0-1.5 × 106 cfu/ml. Using 4,5-dichloro-2-(n-octyl)-4-isothiazolin-3-one (SeaNine 211) as a representative toxic chemical, we evaluated the extent of its toxicity in terms of present method, where 50% effective concentration (EC50) resulted in 0.51 and 0.35 mg/l at 15 and 30 min of incubations, respectively. Sensitivity of present assay was higher than those of traditional ones by over 2 folds from the comparison of EC50 for Cu2+. The results show that the present assay using freshly cultured V. fischeri has not only high sensitivity and reproducibility but also simplicity to estimate the contamination by chemicals.
