Marine Bacteria under Low-Intensity Radioactive Exposure: Model Experiments

Abstract

Radioactive contaminants create problems all over world, involving marine ecosystems, with their ecological importance increasing in the future. The review focuses on bioeffects of a series of alpha and beta emitting radioisotopes (americium-241, uranium-(235 + 238), thorium-232, and tritium) and gamma radiation. Low-intensity exposures are under special consideration. Great attention has been paid to luminous marine bacteria as representatives of marine microorganisms and a conventional bioassay system. This bioassay uses bacterial bioluminescence intensity as the main testing physiological parameter; currently, it is widely applied due to its simplicity and sensitivity. Dependences of the bacterial luminescence response on the exposure time and irradiation intensity were reviewed, and applicability of hormetic or threshold models was discussed. A number of aspects of molecular intracellular processes under exposure to low-intensity radiation were analyzed: (a) changes in the rates of enzymatic processes in bacteria with the bioluminescent system of coupled enzymatic reactions of NADH:FMN-oxidoreductase and bacterial luciferase taken as an example; (b) consumption of an intracellular reducer, NADH; (c) active role of reactive oxygen species; (d) repairing of the DNA damage. The results presented confirm the function of humic substances as natural radioprotectors.

For Special Issue “Molecular Mechanisms of Responses to Low-Intensity Exposures 2.0” of International Journal of Molecular Sciences

“…The results presented contribute to understanding the molecular mechanism of "hormetic" responses to low concentrations of bioactive compounds and low-intensity radioactivity. One of the findings of this Special Issue is that the time of low-intensity exposure is a critical parameter in hormetic responses, along with the dose and type of active compounds [4]. Similar conclusions were reported previously by Sthijns and coauthors [5].…”

“…The bioluminescence activation stage (stage II) in the presence of Gd-containing fullerenol is evident in Figure 1. The advantages of bacterial bioluminescent bioassays were applied while studying the bioactivity of iron oxide nanoparticles [11] and different types of low-dose radioactivity [4].…”

“…The review by Kolesnik and coauthors [4] focused on low-dose bioeffects of a series of alpha and beta emitting radionuclides (americium-241, thorium-232, uranium-(235 + 238), and tritium), as well as gamma radiation. The applicability of hormetic and threshold models was discussed for radionuclides and gamma radiation, respectively.…”

“…Dependences of the bacterial luminescence response on the irradiation intensity and exposure time were reviewed under the conditions of low-dose exposures. Several aspects of molecular intracellular mechanisms under low-intensity irradiation were analyzed: changes in the rates The advantages of bacterial bioluminescent bioassays were applied while studying the bioactivity of iron oxide nanoparticles [11] and different types of low-dose radioactivity [4].…”