Rijstenbil J W, Sandee A, Van Drie J, Wijnholds J A
Netherlands Institute of Ecology, Centre for Estuarine and Coastal Ecology, Yerseke, The Netherlands.
FEMS Microbiol Rev. 1994 Aug;14(4):387-96. doi: 10.1111/j.1574-6976.1994.tb00113.x.
Effects of cadmium (10 nM), copper (80 nM) and zinc (150 nM) additions were studied in the marine diatom Ditylum brightwellii and the riverine diatom Thalassiosira pseudonana. Defense against oxidative stress via cellular thiol (SH) pools and superoxide dismutase (SOD) activation, detoxification via phytochelatins and cell damage were monitored in metal-exposed exponential-phase cells and controls, grown in estuarine medium. Total SH and reduced+oxidized glutathione (GSH+GSSG) in T. pseudonana were much higher than in D. brightwellii. In T. pseudonana, total SH and GSH decreased at 322 nM Zn, and GSH increased at 80 nM Cu but decreased at 119 nM Cu. GSH:GSSG ratios were low, while phytochelatins were not detectable in metal-exposed D. brightwellii. Cd-exposed T. pseudonana made more phytochelatins than Cu-exposed cells, and in different proportions. At 322 nM Zn, SOD activity decreased in T. pseudonana. Zn caused a major, and Cu a minor increase of SOD activity in D. brightwellii; inhibition of photosynthesis was observed in Cu-exposed D. brightwellii, probably due to oxidative damage. The C:N ratios were higher and protein contents lower in Cu-exposed cells of both species, which might indicate excretion due to a loss of cell membrane integrity. From these results, it is hypothesized that T. pseudonana has evolved an effective detoxification mechanism as a result of a more severe exposure to toxic metals in rivers and estuaries. In contrast, D. brightwellii, a marine-estuarine species, cannot adjust well to metal exposure. Its poor defense against metal toxicity was marked by low SH-contents.
研究了添加镉（10 nM）、铜（80 nM）和锌（150 nM）对海洋硅藻布氏双尾藻（Ditylum brightwellii）和河流硅藻假微型海链藻（Thalassiosira pseudonana）的影响。在河口培养基中生长的处于指数生长期的金属暴露细胞和对照细胞中，监测了通过细胞硫醇（SH）池和超氧化物歧化酶（SOD）激活来抵御氧化应激、通过植物螯合肽进行解毒以及细胞损伤情况。假微型海链藻中的总SH以及还原型+氧化型谷胱甘肽（GSH+GSSG）含量远高于布氏双尾藻。在假微型海链藻中，当锌浓度为322 nM时总SH和GSH含量下降，当铜浓度为80 nM时GSH含量增加，但当铜浓度为119 nM时GSH含量下降。GSH:GSSG比值较低，而在金属暴露的布氏双尾藻中未检测到植物螯合肽。暴露于镉的假微型海链藻产生的植物螯合肽比暴露于铜的细胞更多，且比例不同。当锌浓度为322 nM时，假微型海链藻中的SOD活性下降。锌导致布氏双尾藻中SOD活性大幅增加，而铜导致小幅增加；在暴露于铜的布氏双尾藻中观察到光合作用受到抑制，这可能是由于氧化损伤。两种藻类中暴露于铜的细胞的C:N比值较高而蛋白质含量较低，这可能表明由于细胞膜完整性丧失而导致排泄。从这些结果推测，由于在河流和河口接触到更严重的有毒金属，假微型海链藻进化出了一种有效的解毒机制。相比之下，作为一种海洋 - 河口物种的布氏双尾藻对金属暴露的适应性较差。其对金属毒性的防御能力较弱表现为SH含量较低。
