Radiation tolerance of Pseudanabaena catenata, a cyanobacterium relevant to the First Generation Magnox Storage Pond.

Recently a species of Pseudanabaena was identified as the dominant photosynthetic organism during a bloom event in a high pH (pH ~11.4), radioactive spent nuclear fuel pond (SNFP) at the Sellafield Ltd. UK facility. The metabolic response of a laboratory culture containing the cyanobacterium Pseudanabaena catenata, a close relative of the major photosynthetic microorganism found in the SNFP, to X-ray irradiation was studied to identify potential survival strategies used to support colonisation of radioactive environments. Growth was monitored and the metabolic fingerprints of the cultures, during irradiation and throughout the post-irradiation recovery period, were determined using Fourier transform infrared (FT-IR) spectroscopy. A dose of 95 Gy delivered over 5 days did not significantly affect growth of P. catenata, as determined by turbidity measurements and cell counts. Multivariate statistical analysis of the FT-IR spectral data revealed metabolic variation during the post irradiation recovery period, with increased polysaccharide and decreased amide spectral intensities. Increases in polysaccharides were confirmed by complementary analytical methods including total carbohydrate assays and calcofluor white staining. This observed increased production of polysaccharides is of significance, since this could have an impact on the fate of the radionuclide inventory in the pond via biosorption of cationic radionuclides, and may also impact on downstream processes through biofilm formation and biofouling.

近期，英国塞拉菲尔德有限公司（Sellafield Ltd.）设施内的高pH（pH≈11.4）放射性乏核燃料池（SNFP）发生水华事件，其中一种假颤藻属（Pseudanabaena）物种被确定为优势光合生物。本研究以含有蓝细菌链状假颤藻（Pseudanabaena catenata）的实验室培养物为对象，该菌株与该乏核燃料池中发现的优势光合微生物亲缘关系相近，探究其对X射线辐照的代谢响应，以揭示其在放射性环境中定殖的潜在生存策略。研究通过浊度测定与细胞计数监测菌株生长情况，并利用傅里叶变换红外（FT-IR）光谱法分析辐照期间及辐照后恢复全过程中培养物的代谢指纹图谱。经5天辐照、总剂量95 Gy的处理后，链状假颤藻的生长未受到显著影响，该结果通过浊度测定与细胞计数得以验证。对FT-IR光谱数据的多变量统计分析显示，辐照后恢复阶段菌株代谢发生显著变化，表现为多糖相关光谱信号增强，而酰胺类相关信号减弱。通过总碳水化合物测定、荧光增白剂（calcofluor white）染色等互补分析方法，验证了菌株多糖合成量的提升。本研究观察到的多糖合成量提升具有重要意义——这一现象可通过阳离子放射性核素的生物吸附作用影响池中放射性核素的归趋，同时还可能通过生物膜形成与生物污损对后续处理流程产生影响。