Parameters Optimization for Improving Bioluminescence Inhibition Assay Using Vibrio fischeri Bacteria to Detect Lipopolysaccharide Toxicity in Aquatic Environments.

Bioluminescence inhibition of Vibrio fischeri is a widely used method for toxicity testing in aquatic environments. Certain complex biological contaminants, such as lipopolysaccharide (LPS), can interfere with metabolic pathways during toxicity assays. The standard 15-minute Vibrio fischeri bioluminescence assay has limitations when evaluating and screening water toxicity against complex and emerging chemicals like LPS. To accurately determine the effects of such substances, it is crucial to use a bioassay that encompasses a sufficient cell cycle period. This study tested LPS at varying incubation times (ranging from 60 s to 60 min) and concentrations (1-1*10^- 12 mg/ml) to identify the appropriate incubation time for bioluminescence inhibition and toxicity testing. The results indicated that bioluminescence inhibition begins within 60 s and reaches maximum inhibition at 60 min. However, at 30 and 45 min, the bacterial response to different concentrations of LPS varied, with some concentrations causing increased bioluminescence. The EC₅₀ values at different times (60 s, 15, 30, 45, and 60 min) were found to be 0.0012, 0.0063, 4.07e + 54, 3.85e-8, and 3.34e-9 mg/ml respectively. This study highlights the importance of considering incubation time when using bioluminescence inhibition to detect acute toxicity in aquatic ecosystems. A longer incubation time may enhance the method's sensitivity and improve its ability to detect low levels of toxins, such as LPS, in water resources.