Effect of americium-241 on luminous bacteria. Role of peroxides

The effect of americium-241 (²⁴¹Am), an alpha-emitting radionuclide of high specific activity, on luminous bacteria Photobacterium phosphoreum was studied. Traces of ²⁴¹Am in nutrient media (0.16-6.67 kBq/L) suppressed the growth of bacteria, but enhanced luminescence intensity and quantum yield at room temperature. Lower temperature (4 °C) increased the time of bacterial luminescence and revealed a stage of bioluminescence inhibition after 150 h of bioluminescence registration start. The role of conditions of exposure the bacterial cells to the ²⁴¹Am is discussed. The effect of ²⁴¹Am on luminous bacteria was attributed to peroxide compounds generated in water solutions as secondary products of radioactive decay. Increase of peroxide concentration in ²⁴¹Am solutions was demonstrated; and the similarity of ²⁴¹Am and hydrogen peroxide effects on bacterial luminescence was revealed. The study provides a scientific basis for elaboration of bioluminescence-based assay to monitor radiotoxicity of alpha-emitting radionuclides in aquatic solutions.     

The influence of quinones and phenols on the triple NAD(H)-dependent enzyme systems

Kinetics of the triple bioluminescent enzyme system: alcohol dehydrogenase--NADH:FMN-oxidoreductase--luciferase in the presence of quinones and phenols has been studied. The correspondence between the bioluminescent kinetic parameters, redox potentials and concentrations of the quinones and phenols has been estimated. The substances have been shown to change bioluminescent kinetics through moving off the NAD+/NADH balance in the enzyme processes. This system is proposed to be used as enzymatic biotest in ecological monitoring.