In this study, the removal of cadmium (Cd) by free-living Oscillatoria sp. was studied. Our results showed that maximal Cd removal efficiency (~60%) by the cyanobacterial culture was achieved within 12–24 h in the presence of 5.0 or 25.0 mg/L of Cd. The mechanisms underlying this phenomenon were explored by elemental analysis and FTIR-ATR spectroscopy. It was found that metal adsorption by negatively charged functional groups in the cyanobacterial biomass was the main mechanism used by Oscillatoria sp. to remove metal from the aqueous medium, followed by Cd bioaccumulation into living cells. Additionally, Cd-exposed microalgae showed increased oxidative stress (MDA formation), a decreased dehydrogenase activity, a higher amount of soluble carbohydrates and a decreased total carotenoid concentration, as compared to the control cells. These results suggest that Oscillatoria sp. improved its antioxidative defense system under stressful conditions, through carotenoid-mediated ROS quenching and induction of carbohydrate catabolism, in order to counteract the oxidative damage and preserve the photosynthetic machinery and cellular energetics. In fact, no significant reduction in Oscillatoria sp. cell density, total protein amount, and chlorophyll a content was observed after 24-h Cd exposure, even at the highest metal concentration tested (i.e., 25.0 mg/L). Hence, the presented results are the first to describe some new insights about the metabolic and physiological behavior of living Oscillatoria sp. during Cd remediation, and open up the possibility of finding an equilibrium that maximizes metal removal performance with an active cyanobacterial metabolism, to achieve a rewarding and sustainable management of industrial metal-polluted wastewater.

中文翻译：

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使用游离蓝细菌（Oscillatoria sp。）处理镉污染的水的前景

在这项研究中，通过自由生活的Oscillatoria sp。去除镉（Cd）。被研究了。我们的结果表明，在存在5.0或25.0 mg / L的Cd的情况下，通过蓝细菌培养实现的最大Cd去除效率（〜60％）在12-24小时内达到。通过元素分析和FTIR-ATR光谱研究了该现象的潜在机理。发现蓝藻生物质中带负电荷的官能团对金属的吸附是颤藻的主要作用机理。sp。从水介质中去除金属，然后将Cd生物富集到活细胞中。另外，与对照细胞相比，镉暴露的微藻显示出增加的氧化应激（MDA形成），降低的脱氢酶活性，较高的可溶性碳水化合物含量和降低的总类胡萝卜素浓度。这些结果表明，Oscillatoria sp。通过抵抗类胡萝卜素介导的ROS猝灭和诱导碳水化合物分解代谢，改善了其在抗压条件下的抗氧化防御系统，从而抵消了氧化损伤并保护了光合作用机制和细胞能量。事实上，在没有显著减少颤sp。即使在测试的最高金属浓度（即25.0 mg / L）下，暴露24 h Cd后仍能观察到细胞密度，总蛋白质量和叶绿素a含量。因此，提出的结果是第一个描述有关生活Oscillatoria sp。的代谢和生理行为的新见解的人。在Cd修复过程中，找到了一个平衡的可能性，该平衡可通过活性蓝细菌代谢最大化金属去除性能，从而实现对工业金属污染废水的有益且可持续的管理。