γ射线辐照对细胞外质粒DNA转化效率的影响。

Impact of gamma irradiation on the transformation efficiency for extracellular plasmid DNA.

作者信息

Ishii Nobuyoshi, Sakashita Testuya, Takeda Hiroshi, Kubota Yoshihisa, Fuma Shoichi, Doi Masahiro, Takahashi Sentaro

机构信息

Environmental and Toxicological Sciences Research Group, National Institute of Radiological Sciences, Anagawa 4-9-1, Chiba 263-8555, Japan.

出版信息

J Environ Radioact. 2007;97(2-3):159-67. doi: 10.1016/j.jenvrad.2007.04.002. Epub 2007 Jun 1.

DOI:10.1016/j.jenvrad.2007.04.002

PMID:17544184

Abstract

Extracellular DNA is omnipresent in aquatic environments and is thought to be a genetic material for horizontal gene transformation between microorganisms. We studied the impact of gamma irradiation on the transformation efficiency (transformants number per ng of DNA per ml) of extracellular DNA. Plasmid pEGFP as a model extracellular DNA was irradiated by gamma rays. The transformation efficiency decreased with the increase in radiation dose. A total dose of 10Gy is normally not lethal for microorganisms but certainly affects the transformation efficiency of extracellular DNA. The decrease in the efficiency would be induced by strand breaks of extracellular DNA because the yield of both single-strand breaks (SSBs) and double-strand breaks (DSBs) increased with the increase in radiation dose. The relative transformation efficiency of SSBs and DSBs to that of covalently closed circles (CCCs) was 30.3% and 0.2%, respectively. This impact on natural transformation suggests an inability of microorganisms to acquire new characteristics which should be normally acquired.

摘要

细胞外DNA在水生环境中普遍存在，被认为是微生物之间水平基因转移的遗传物质。我们研究了γ射线辐照对细胞外DNA转化效率（每毫升每纳克DNA的转化子数）的影响。以质粒pEGFP作为模型细胞外DNA进行γ射线辐照。转化效率随辐射剂量的增加而降低。总剂量10Gy通常对微生物不具有致死性，但肯定会影响细胞外DNA的转化效率。效率的降低是由细胞外DNA的链断裂引起的，因为单链断裂（SSB）和双链断裂（DSB）的产量都随辐射剂量的增加而增加。SSB和DSB相对于共价闭合环状（CCC）的相对转化效率分别为30.3%和0.2%。这种对自然转化的影响表明微生物无法获得通常应获得的新特性。