微藻砷代谢的氮磷营养调控机理研究

Microalgae have good application prospects in the development of new health products and purification of arsenic (As) polluted water. Nevertheless, the quality of products and the effectiveness of As remediation may be affected by As metabolism pathways and products in the algal cells. A large number of studies showed that As uptake and metabolism varied considerably among different microalgae and the same algae under different conditions, but the reasons for these differences have not been clarified. We hypothesize that these variations may be related to the effects of nitrogen (N)/phosphorus (P) nutritional status on the algal growth and physiology, which may lead to the difference of As content and speciation, based on our previous research on the As speciation in marine algae. In order to varify the above hypothesis, this project will grow different types of algae, set up various conditions of exogenous N/P quantity, speciation and ratios, and conduct As toxicological experiments. State-of-art HPLC-MS/GC-MS techniques will be applied to analyze the dynamics of As speciation in microalgae and to investigate the relationships among As, thiol and lipid metabolisms, and to elucidate the regulatory mechanisms of As metabolism in microalgae by N and P. The results of this research may be of great significance in safeguarding the quality of microalgae products, achieving the bioremediation of As pollution in seawater, and reducing the risks of this toxic element to the environment and human health.

微藻在新型保健品开发和砷污染水体净化上具有良好的应用前景，其产品质量和修复效果受到藻细胞中砷的代谢途径和产物的影响。大量研究表明，不同微藻或者同种微藻在不同条件下对砷的吸收和代谢规律具有明显差异，然而造成这些不同结果的原因尚不清楚。本项目在课题组针对海藻砷赋存形态开展的前期工作基础上，提出“外源氮磷养分条件制约着微藻生长和代谢过程，由此带来藻细胞内砷含量和赋存形态的差异”。为验证这个假设，本项目将采用不同类型微藻，设置外源氮、磷养分的丰缺、形态、比例等条件，运用先进的色谱—质谱联用技术，结合砷毒理学实验，分析微藻中砷的赋存形态及其动态变化，解析砷代谢与巯基以及脂类代谢的关系，以期揭示微藻砷代谢的氮磷营养调控机制。本研究结果对于保障微藻产品的品质安全、实现水体砷污染的生物修复、降低砷对生态环境和人体健康的风险具有十分重要的意义。

微生物砷代谢的途径和产物受到周围环境条件的影响。针对微藻砷富集和代谢结果多样、规律不清的问题，本项目采用不同微藻，研究了微藻对砷（砷酸盐和亚砷酸盐）的耐性、富集和代谢规律及氮磷的影响机制。结果表明：.1）氮对微藻生长影响远大于磷的影响。微藻对砷的吸附、吸收和转化受到磷酸盐的显著影响，磷酸盐缺乏促进微藻砷酸盐和亚砷酸盐的吸收、砷酸盐的还原和甲基化的数量和速度，反之，磷酸盐充足时微藻砷酸盐吸收降低，还原受到抑制（Wang et al. Environmental Science: Processes & Impacts 2016；Wang et al. Environmental Science and Pollution Research 2017；王淑等2015；刘聪等2016）。.2）砷酸盐还原酶的表达和活性显著影响莱茵衣藻对砷和磷的吸收，敲除该酶的莱茵衣藻突变体对砷的富集显著低于对照，而磷的含量则显著高于对照。突变体的砷酸盐还原速率显著降低（郑燕恒2017）。.3）微藻胞内巯基物质含量与砷、磷处理关系密切，磷酸盐增加减少了微藻对砷的吸收，也降低了巯基物质的合成（Wang et al. Ecotoxicology and Environmental Safety 2017）。.4）砷酸盐胁迫下微藻通过增加磷酸盐的吸收、强化能量代谢、细胞防御、磷酸盐跨膜运输、蛋白折叠及合成等途径解除砷的毒性效应（Ge et al. Chemosphere 2016）。.以上结果深化了我们对微藻砷富集和代谢规律的认识，对揭示微藻砷解毒的机制、推进微藻在砷污染水体的修复方面都具有重要意义。