Glowing bacteria will help measure radioactivity

Alexandra Sitnikova, SFU Press Service

Siberian biophysicists conducted an experimental study of the biological effect of low-dose gamma radiation. The results of the study are presented in one of the world's leading scientific journals on environmental radioactivity, Journal of Environmental Radioactivity (Kudryasheva et al., Exposure of luminous marine bacteria to low-dose gamma-radiation).

During the experiments , scientists were interested in the following issues relevant to radiobiology:

• what are the features of the effects of low-dose gamma radiation on living beings;
• what are the differences between the effects of gamma radiation on living organisms from alpha and beta radiation.

The luminous bacteria Photobacterium phosphoreum were used as a test organism, which are an extremely convenient object for analyzing all aspects of radiation exposure. "Hot particles" containing cesium-137 found in the bottom sediments of the Yenisei River near the village of Atamanovo in the Krasnoyarsk Territory were used as sources of gamma radiation. To conduct the study, the glowing bacteria were placed in an experimental capsule, where they were exposed to radiation of varying power and duration, at three temperatures (+5 °C, +10 °C, +20 °C).

Studies of the effects of gamma radiation are particularly relevant due to the fact that, unlike alpha and beta radiation, gamma radiation poses the greatest danger. The degree of its spread and penetration is the most extensive, and it cannot be completely protected from any material. For example, a simple sheet of paper is enough to hide from alpha radiation, and only absorbing layers of heavy metals, such as lead, can protect against gamma radiation.

Differences in the biological effects of different types of radiation (alpha, beta and gamma) are related to the nature of these radiations. Thus, alpha and beta radiation are streams of charged particles (respectively, the nuclei of helium atoms and electrons) and actively ionize the environment. Gamma radiation is a high-energy electromagnetic radiation and is characterized by a low ionizing ability. It is these differences that should affect the biological effects not only with high-dose, but also with low-dose effects. Low-dose effects are currently the least studied and therefore the most interesting for scientists.

As a result of the conducted experiments and comparison with the conclusions of previous studies in this area, scientists have come to several significant conclusions.

• Firstly, if the effect of low-intensity alpha and beta radiation on living organisms can be described by the hormesis model (according to which radiation radiation can have not only a negative, but also a positive effect), then for low-intensity gamma radiation under similar conditions, only an overwhelming effect is detected, which is described by a linear dependence in dose-the effect.

• Secondly, scientists have found that with low-intensity radiation exposure, the absorbed dose of radiation is not as important as its duration, which is crucial for toxic effects on organisms.

• Thirdly, as a result of exposure to low-dose gamma radiation on glowing bacteria at temperatures of +5°C and +10 °C, scientists did not register any suppressive radiation effect during the experiment (up to 175 hours). With a similar effect of gamma radiation at a temperature of +20 ° C, the researchers observed suppression of the natural glow of marine bacteria, therefore, these organisms were exposed to toxic effects. Scientists explain this by the fact that at higher temperatures, metabolic processes accelerate, and bacteria become more sensitive to radiation exposure.

• And, fourthly, if the danger of radiation exposure is often associated with changes at the genetic level, then at low doses of gamma radiation, scientists have not found changes in the genes responsible for the vital functions of bacteria.

According to one of the co-authors of the publication, Professor of the Siberian Federal University and scientist of the Institute of Biophysics SB RAS Nadezhda Kudryasheva, the results of this study are of both fundamental and applied importance: "The results obtained help to understand the nature of the biological effects of low-intensity radiation at the cellular level. Cells of luminous bacteria are an extremely convenient object for such studies. The applied aspect of the work is related to the possibility of using luminous bacteria to determine (monitor) environmental toxicity. It is known that these bacteria have been widely used for about fifty years to monitor the toxicity of the environment when contaminated with chemicals. Our research shows the prospects of using these bacteria to determine (monitor) toxicity in radioactive contamination."

Portal "Eternal youth" http://vechnayamolodost.ru  15.03.2017