MOE Laboratory for Earth Surface Process, College of Urban & Environmental Sciences, Peking University, Beijing, China.
Environ Toxicol Chem. 2013 Dec;32(12):2762-70. doi: 10.1002/etc.2362. Epub 2013 Oct 1.
The toxic effects of cadmium (Cd) on the green alga Chlorella vulgaris were investigated by following the response to Cd of various toxicity endpoints (cell growth, cell size, photochemical efficiency of PSII in the light or Φ(PSII), maximal photochemical efficiency or Fv/Fm, chlorophyll a fluorescence, esterase activity, and cell viability). These toxicity endpoints were studied in laboratory batch cultures of C. vulgaris over a long-term 96-h exposure to different Cd concentrations using flow cytometry and pulse amplitude modulated fluorometry. The sequence of sensitivity of these toxicity endpoints was: cell yield >> Φ(PSII) ≈ esterase activity > Fv/Fm > chlorophyll a fluorescence ≈ cell viability. It is shown that cell apoptosis or cell death only accounted for a minor part of the reduction in cell yield even at very high algistatic free Cd²⁺ concentrations, and other mechanisms such as blocked cell divisions are major contributors to cell yield inhibition. Furthermore, cadmium may affect both the electron donors and acceptors of the electron transport chain at high free Cd²⁺ concentration. Finally, the resistance of cells to cell death was size-dependent; medium-sized cells had the highest toxicity threshold. The present study brings new insights into the toxicity mechanisms of Cd in C. vulgaris and provides a detailed comparison of the sensitivity of various Cd toxicity endpoints.
采用流式细胞术和脉冲幅度调制荧光仪，在实验室分批培养中，对不同浓度 Cd 进行了为期 96 小时的长期暴露实验，研究了 Cd 对绿藻小球藻的各种毒性终点（细胞生长、细胞大小、PSII 在光下的光化学效率 Φ(PSII)、最大光化学效率或 Fv/Fm、叶绿素 a 荧光、酯酶活性和细胞活力）对 Cd 的响应，以此来研究 Cd 的毒性效应。这些毒性终点的敏感性顺序为：细胞产量＞Φ(PSII)≈酯酶活性＞Fv/Fm＞叶绿素 a 荧光≈细胞活力。结果表明，即使在非常高的藻抑制游离 Cd²⁺浓度下，细胞凋亡或细胞死亡仅占细胞产量减少的一小部分，而其他机制，如细胞分裂受阻，是细胞产量抑制的主要原因。此外，Cd 在高游离 Cd²⁺浓度下可能会影响电子传递链的电子供体和受体。最后，细胞对细胞死亡的抵抗力与细胞大小有关；中等大小的细胞具有最高的毒性阈值。本研究为小球藻中 Cd 的毒性机制提供了新的见解，并对各种 Cd 毒性终点的敏感性进行了详细比较。
