锶诱导的氧化胁迫对叉鞭金藻(Dicrateria inornata)的影响

STRONTIUM STRESS ON MARINE MICROALGAE DICRATERIA INORNATA GROWTH AND ANTIOXIDANT ENZYMES ACTIVITIES

采用不同浓度的锶胁迫方法研究了叉鞭金藻生长、叶绿素、MDA含量及三种抗氧化酶SOD、CAT、GPX活性的变化。结果表明 ,在实验设计的各种Sr2 +浓度内叉鞭金藻均能生长 ,但Sr2 +浓度较高时生长受到不同程度的抑制 ,细胞数量比对照组分别减少 1 5 .9%和 5 1 .0 % ;叉鞭金藻中叶绿素含量随着Sr2 +浓度的升高而降低 ,呈负相关关系 ;叉鞭金藻中MDA含量在较低Sr2 +浓度下稍呈下降趋势 ,但与对照组相比并无显著差异 ,而在 2 3.0 4mmol/LSr2 +浓度时是对照的 1 .2 3倍 ;低Sr2 +浓度时 ,叉鞭金藻中蛋白质含量没有大的变化 ,当浓度超过 5 .76mmol/L时则引起蛋白质含量下降 ;叉鞭金藻中抗氧化酶SOD在低Sr2 +时分别降低 1 2 .5 %、7.5 %和 9.5 % ,高Sr2 +时显著升高 ,为对照组的 85 .7% ;CAT、GPX活性在低Sr2 +浓度时差别不大 ,但当浓度为 2 3.0 4mmol/L时升高显著 ,比对照组分别增加了 1 9.8%和 74.4%。

Increasing utilization of heavy metals in industries has caused serious environmental pollution. They were transported into marine environment and accumulated without decomposition, which has become a major concern in recent years. Strontium is a minor component of seawater but is a major hazardous contaminant from the sludge generated by nuclear industry released regularly or accidentally. 90 Sr, a normal by-product of nuclear fission, can reside in natural environment. When strontium isomorphously replaces the calcium in animal bones, it becomes more mobile than calcium, and used to cause Urov′s disease. Therefore, strontium is ranked as one of the most potential hazardous element to humans and aquatic organisms. The present study is to investigate the strontium effects in elevated concentrations on growth, lipid peroxidation and some antioxidant enzymes activities of marine microalgae Dicrateria inronata. Sample marine microalgae D. inornata were provided by Institute of Oceanology, Chinese Academy of Sciences, Qingdao. It was maintained in sterilized artificial seawater enriched with f/2 medium. The algae grew at (24 ± 1)℃, 120μmol photon/(m 2·s), 12h : 12h L/D cycle. The experiments were conducted in 500 ml flasks autoclaved at 121℃ for 20 min. Strontium-bearing solutions were prepared by dissolving analytical grade strontium chloride in deionized water. Sr 2+ solutions in the range 0.09 to 23.04mmol/L were prepared by diluting concentrated stock solution. Growth of microalgae was measured spectrophotometrically at 420nm in a cuvette with a 1-cm light path. OD 420 values were converted to cell counts using liner regressions between optical density and cell counts determined in preliminary experiments (y = 50.69OD 420 + 0.93, r = 0.999, cell counts = y × 10 5). For enzymes assays, D. inornata samples were centrifuged and re-suspended in 1/15 mmol of pre-cooled sodium phosphate buffer (pH 7.0). After sonication in an ice bath, the cell debris was removed by centrifugation at high speed. The supernatant was used for enzyme activity assay.The results show that D. inornata could grow under all experimental conditions. Growth was not inhibited significantly by strontium constraint whose concentration is lower than 1.14mmol/L. However, 5.76mmol/L and above, significant reduction in the number of microalgal cells were apparent. Growth was inhibited by 15.9 % and 51.0 %, when compared to the control at strontium treatment concentrations of 5.76 and 23.04mmol/L respectively. Meanwhile, chlorophyll a content varied from 0.72 to 2.32μg/ml as strontium concentration increased. At 23.04mmol/L, chlorophyll a content reached the minimum. Protein content remained relatively similar at concentrations up to 5.76mmol/L. Once at 23.04mmol/L, a significant (49.7%) decrease was observed. MDA content decreased significantly at 0.09, 0.36, 1.14 and 5.76mmol/L concentrations. But after 23.04mmol/L, MDA increased significantly to 123.0% of that in the control. In the case of antioxidase activities, SOD decreased between 7.5% to 12.5%, at lower strontium levels; and increased remarkedly at higher levels, 85.7% more than the control. Significant increments in CAT and GPX activities were also seen which is 19.8% and 74.4% respectively higher than the control at the strontium concentration of 23.04mmol/L. A decrease in SOD and CAT activities are evident at lower external concentrations whereas GPX activity was not significantly affected by concentrations lower than 23.04mmol/L. Studying antioxidant system under the stress of strontium could be a new approaches in microalgae research. In conclusion, D. inornata can induced some antioxidant enzymes, which are important protective material to minimize cell oxidative damage by pollution. D. inornata is able to live in high strontium concentrated areas.