All organisms are exposed to low level background of environmental radiation every day. Usually, with little detriment to their existence. In contrast, ionizing radiation associated with
naturally occurring radioactive material, mining sites, or from anthropogenic release from nuclear power plants or nuclear accidents, have the potential to pose a significant environmental risk.
“The ability of organisms to tolerate radiation exposure can vary by more than 1000-fold,” PhD candidate Erica Maremonti says.
“However, the underlying biological mechanisms behind this variation is poorly understood.”
Important to understand negative effects
Because of the large differences between species, how ecosystems react to radiation contamination are highly dependent on what species live there.
“Therefore, it is vital that we understand what factors influence radiosensitivity, so that we can assess the risk to species, populations and ecosystems,” Maremonti explains.
She has in her PhD project assessed the effects of chronic exposure to low-dose ionizing
gamma radiation in the radioresistant nematode Caenorhabditis elegans.
She has investigated adverse effects of radiation from a molecular to a cellular, tissue and individual level.
Good model organism
“This nematode is a good model organism for several reasons,” she says.
C. elegans is a nematode worm and is significantly anatomically simpler than a human, however, it does share many similarities at the molecular level, thus making it a good candidate for a model organism.
The worm is transparent throughout its life so the behavior of individual cells can be followed through its development. The anatomy and development can therefore be easily examined under a microscope.
Affected by radiation
Maremonti’s experiments showed that even a radiation tolerant organism like the C. elegans-nematode, is affected by low doses of gamma radiation.
Her results also showed that earlier larval stages were more vulnerable than later stages.
In line with previous studies, she found adverse effects on reproduction.
“The nematodes’ reproductive apparatus is a vulnerable target for chronic low-dose gamma irradiation due to high cell proliferation in the gonadal tissues,” she comments.
Activates defense systems
This study also showed that C. elegans do mount multiple defense responses, including
DNA repair and antioxidant defenses when subjected to chronic irradiation.
“These defense mechanisms ameliorate radiation damage in somatic cells, and thus provide tolerance towards chronic exposure to ionizing radiation,” Maremonti says.
The mitochondria and the mitochondrial DNA comprise a sensitive target to radiation and the nematodes activate defense mechanisms to counteract mitochondrial dysfunction.
Maremonti’s findings help to understand similarities and dissimilarities between radiosensitive and radioresistant species. In a wider context her study can provide new insight in the field of radiation biology and mechanisms of toxicity of ionizing radiation.