Comparative responses of microscopic fungi to ionizing radiation and light

Abstract

Microscopic fungi of 47 species and 24 genera isolated from radioactive soil and other radioactive substrates of a 10-km alienation zone from Chernobyl Nuclear Power Plant were investigated. Only 19 % of such fungi showed toward the ionizing irradiation source positive radiotropism. Strains with best-defended radiotropism responded to the influence of weak white light. Both of these responses (radiotropism and photostimulation) were of an adaptive nature, were found in both dark-colored and light-colored micromycetes and were probably a strain-related feature.

Ionizing radiation: how fungi cope, adapt, and exploit with the help of melanin

“…They named this phenomenon “radioadaptive response”. They also observed the same results for responses of fungi from contaminated areas to light (20). However, though the presence of adaptive properties in fungi exposed in the long term to elevated radiation levels are very likely, the limitations of the experimental work reported in (18–20) might interfere with the authors’ ability to observe the radiostimulation for fungi from the clean areas as well.…”

“…They also observed the same results for responses of fungi from contaminated areas to light (20). However, though the presence of adaptive properties in fungi exposed in the long term to elevated radiation levels are very likely, the limitations of the experimental work reported in (18–20) might interfere with the authors’ ability to observe the radiostimulation for fungi from the clean areas as well. For example, the activity of the radioactive sources used in the later studies (18–20) was approximately 1,000 lower than used in earlier work (17) which might have been insufficient to promote the hyphal growth.…”

“…They concluded that inducible MHMR pathway could be a potential mechanism of adaptive evolution in eukaryotes. These observations might explain the radioadaptive response in fungi described by Zhdanova group (18–20), but are an unlikely explanation for the enhanced growth effects of irradiated melanized organisms, which responded within hours.…”

“…However, though the presence of adaptive properties in fungi exposed in the long term to elevated radiation levels are very likely, the limitations of the experimental work reported in (18–20) might interfere with the authors’ ability to observe the radiostimulation for fungi from the clean areas as well. For example, the activity of the radioactive sources used in the later studies (18–20) was approximately 1,000 lower than used in earlier work (17) which might have been insufficient to promote the hyphal growth. This may have been the case especially for low energy 121 Sn; also, the beta particles from 137 Cs might have been absorbed by the material of the Petri dish with the fungi as the collimated beam was coming from beneath and thus have not contributed to the actual radiation doses which could have been overestimated.…”

Threats Posed by the Fungal Kingdom to Humans, Wildlife, and Agriculture

“…Fungi are important members of diverse microbiota and promote ecosystem homeostasis through interactions with bacteria in lungs, guts, soil, stems, and other environments ( 8 – 10 ). Although fungi are generally considered auxotrophic, they can also harvest electromagnetic radiation for growth, which implies some autotrophic capacity ( 11 – 13 ). Fungi are highly resilient and capable of successfully occupying extreme environments.…”