Rogers N J, Apte S C, Knapik A, Davies C M, Bowles K C, Kable S H
Centre for Environmental Contaminants Research, CSIRO Energy Technology, Private Mail Bag 7, Bangor, NSW 2234, Australia.
Arch Environ Contam Toxicol. 2005 Nov;49(4):471-9. doi: 10.1007/s00244-004-0179-9. Epub 2005 Sep 30.
A rapid, highly sensitive bacterial bioassay to determine copper toxicity in freshwaters was developed based on the inhibition of cellular assimilation of radiolabeled glucose. The test used a copper-sensitive bacterium isolated from a freshwater stream. Employing sensitive radiochemical techniques enabled environmentally relevant concentrations of the test bacterium (10(5) cells mL(-1)) and a short incubation period (4 hours) to be used, which minimized the potential for changes in copper speciation during the test. The 4-hour median effective concentration (EC(50)) for inorganic copper at pH 7.5 in synthetic freshwater was 0.6 microg L(-1) (95% confidence limits 0.4 to 1.0 microg L(-1)). This compared well with chronic growth inhibition of this bacterium in minimal medium (48-hour EC(50) of 0.9 microg L(-1) [95% confidence limits 0.7 to 1.0 microg L(-1)]). MINEQL + software (Environmental Research Software) was used to calculate copper (II) ion concentrations in synthetic freshwater at pH 7.5, giving an EC(50) value of pCu(2+) 8.8. However, using nitrilotriacetic acid metal-ion buffers (Cu-NTA), 50% inhibition occurred at a pCu(2+) of 9.7, suggesting this bacterium was markedly more inhibited by copper in these Cu(2+)-buffered solutions. This may indicate that the Cu-NTA species was contributing to toxicity. The radiochemical bioassay was evaluated further using freshwater samples from both copper-impacted and pristine environments. Measured EC(50) values ranged from 3.4 to 34.0 microg L(-1)inorganic copper and were strongly correlated with dissolved organic carbon (DOC) concentrations (r = 0.88, p < 0.05).
基于对放射性标记葡萄糖细胞同化作用的抑制，开发了一种快速、高度灵敏的细菌生物测定法，用于测定淡水中的铜毒性。该测试使用了从淡水溪流中分离出的对铜敏感的细菌。采用灵敏的放射化学技术能够使用与环境相关浓度的测试细菌（10⁵ 个细胞 mL⁻¹）和较短的孵育期（4小时），这最大限度地减少了测试过程中铜形态变化的可能性。在合成淡水中，pH值为7.5时，无机铜的4小时半数有效浓度（EC₅₀）为0.6 μg L⁻¹（95%置信限为0.4至1.0 μg L⁻¹）。这与该细菌在基本培养基中的慢性生长抑制情况（48小时EC₅₀为0.9 μg L⁻¹ [95%置信限为0.7至1.0 μg L⁻¹]）相比良好。使用MINEQL +软件（环境研究软件）计算了pH值为7.5的合成淡水中铜（II）离子浓度，得出pCu(2+)的EC₅₀值为8.8。然而，使用次氮基三乙酸金属离子缓冲液（Cu-NTA）时，在pCu(2+)为9.7时出现50%的抑制，表明该细菌在这些Cu(2+)缓冲溶液中受到铜的抑制作用明显更强。这可能表明Cu-NTA物种对毒性有贡献。使用来自受铜污染和原始环境的淡水样本进一步评估了放射化学生物测定法。测得的无机铜EC₅₀值范围为3.4至34.0 μg L⁻¹，并且与溶解有机碳（DOC）浓度密切相关（r = 0.88，p < 0.05）。
