Bioluminescence of Aliivibrio Fischeri in Artificial Seawater and Its Application in Fungicide Sensing.

It has been well investigated that the bioluminescence (BL) intensity of marine luminous bacteria is enhanced depending on cell density. In contrast, the correlation between seawater components and BL intensity is still a challenging subject to be addressed. In addition, the marine luminous bacteria rapidly lose the BL intensity when exposed to toxic substances, but unclear to fungicides. Herein, we introduce a new approach to investigate (i) the correlation between the components of artificial seawater (ASW) and BL intensity and (ii) the corresponding protocol to determine the susceptibility of marine luminous bacteria to fungicide using A. fischeri. The examples show that (i) ionic ingredients (K+, HCO3-, and SO42-) activate the BL cell density independently and (ii) A. fischeri cultured with the ionic ingredients shows the susceptibility to fungicide (sodium ortho-phenylphenol and imazalil). These protocols provide a new insight how to investigate the correlation between inorganic salts and BL intensity in a low cell density environment such as seawater.

Control of Aliivibrio fischeri Luminescence and Decrease in Bioluminescence by Fungicides.

Studies have reported that cell density, ultraviolet (UV) irradiation, and redox reactions, can induce bioluminescence in bacteria. Conversely, the relationship between seawater components and luminescence is not well understood. The efficacy of marine luminous bacteria as biosensors, and their reactivity to fungicides (for example postharvest pesticides) are also unknown. Therefore, we studied the relationship between the luminescence of Aliivibrio fischeri and the composition of artificial seawater media and analyzed the toxicity of fungicides using A. fischeri grown only with the elements essential to induce luminescence. Luminescence was activated in the presence of KCl, NaHCO3, and MgSO4. In addition, we cultivated A. fischeri with other compounds, including K+, HCO3-, and SO42- ions. These results suggested that A. fischeri requires K+, HCO3-, and SO42- ions to activate cell density-independent luminescence. Additionally, A. fischeri cultured in 2.81% NaCl solutions containing KCl, NaHCO3, and MgSO4 exhibited a decrease in luminescence in the presence of sodium orthophenylphenol at >10 ppm. This result suggests that A. fischeri can be used as a biosensor to detect the presence of sodium ortho-phenylphenol.