Responses of the bacterial community to chronic gamma radiation in a rice paddy ecosystem

Abstract

Purpose: Public concern about radiation protection of the environment and non-human species is increasing. The potential impact of chronic gamma radiation on the bacterial community in a rice paddy ecosystem was investigated.

Materials and methods: Paddy field microcosm samples were continuously exposed at a dose rate of 1 Gy day⁻¹ for five days after which the bacterial community structures in them were compared with those of unirradiated control samples by denaturing gradient gel electrophoresis (DGGE) of the 16S ribosomal ribonucleic acid (rRNA) gene. Dissolved ions in ponding waters of the microcosm samples were determined by ion chromatography.

Results: The DGGE band profiles were clearly different between the control and exposure samples. Sequencing of selected DGGE bands revealed that a specific species of the genus Clostridium and of the genus Massilia were grown under radiation exposure. Additionally, the concentrations of sulphate ion in the ponding water of the microcosm samples increased under radiation exposure. Concentrations of Na⁺, Ca²⁺, and F⁻ inversely decreased.

Conclusions: The data presented suggest that chronic gamma radiation affects the bacterial community structure and material cycles in the rice paddy ecosystem.

Keywords:

• Environmental bacteria
• community structure
• chronic gamma radiation
• nutrient cycling
• paddy soil

Acknowledgements

The authors are grateful to Ms N. Ogiu and Ms A. Matsumoto for assistance with the chemical and biological analyses. This work was funded in part by the Ministry of Education, Culture, Sports, Science and Technology, Grant-in-Aid for Young Scientists (B), 18710051.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.