Effect of tritium on luminous marine bacteria and enzyme reactions

The paper studies chronic effect of tritiated water, HTO, (0.0002–200 MBq/L) on bioluminescent assay systems: marine bacteria Photobacterium phosphoreum (intact and lyophilized) and coupled enzyme reactions. Bioluminescence intensity serves as a marker of physiological activity. Linear dependencies of bioluminescent intensity on exposure time or radioactivity were not revealed. Three successive stages in bacterial bioluminescence response to HTO were found: (1) absence of the effect, (2) activation, and (3) inhibition. They were interpreted in terms of reaction of organisms to stress-factor i.e. stress recognition, adaptive response/syndrome, and suppression of physiological function. In enzyme system, in contrast, the kinetic stages mentioned above were not revealed, but the dependence of bioluminescence intensity on HTO specific radioactivity was found. Damage of bacteria cells in HTO (100 MBq/L) was visualized by electron microscopy. Time of bioluminescence inhibition is suggested as a parameter to evaluate the bacterial sensitivity to ionizing radiation.

► Nonlinear dose–effect relations were found for luminous bacteria in HTO.
► HTO induced three-stage response in bacteria: threshold, activation, inhibition.
► Stability of cells to HTO is higher than that of enzymes.
► Inhibition time is a parameter to evaluate sensitivity of organisms to radiation.