How a Taxonomically-Ambiguous Cyanobiont and Vanadate Assist in the Phytoremediation of Cadmium by Azolla pinnata: Implications for CKDu

D. R. A. M. T. R. Atugoda, L. Mandakini, N. Bandara, D. Gunawardana
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引用次数: 2

Abstract

We employed scientific tools to investigate the ex situ phytoremediation of cadmium by Azolla pinnata. Azolla pinnata was capable of efficient sequestration of cadmium up to a concentration of 1 ppm, though with a visibly high “physiological cost”. The sequestration of cadmium (1 ppm) was strongly reduced after 24 hours, in Azolla plants pre-treated with the gram-negative antibiotic erythromycin (60 µg/l), suggesting that the cyanobacterial population was important for phytoremediation. Only the co-treatment of 1 ppm cadmium with 1 ppm vanadate, showed significantly higher phytoremediation (P<0.05) compared to the “cadmium+erythromycin” treatment. The phytoremediation of Cadmium by the Azolla-Nostoc symbiosis was significantly (p<0.05) improved by the addition of citrate at 10 ppm in the presence of 1 ppm vanadate, compared to the 1 ppm cadmium only treatment. We hypothesize that citrate acting either as “vanadophores” or working as a cofactor in the Homocitrate Synthase enzyme, facilitates remediation of cadmium. When phylogeny was inferred using Homocitrate Synthases, the cyanobiont was approximated to a taxonomical twilight zone between Nostoc and Anabaena, although showing more proximity to the Anabaena cluster. It is proposed here that the cyanobacterial contribution appears to be crucial for the ability of Azolla pinnata to efficiently remediate cadmium and a “helping hand” appears to be provided by a vanadate dependent mechanism, which is likely to be nitrogen fixation. The association between vanadate-assisted phytoremediation by Azolla pinnata and the heightened bioavailability of vanadium in CKDu endemic areas, could serve as a vital stepping stone in developing a biological solution to CKDu.
分类上不明确的蓝藻和钒酸盐如何协助植物修复羽状杜鹃中的镉:对CKDu的影响
采用科学手段研究了凤尾花对镉的迁地修复作用。尽管具有明显的高“生理成本”,但凤尾花能够有效地隔离浓度高达1ppm的镉。经革兰氏阴性抗生素红霉素(60µg/l)预处理后,24小时后,绿藻种群对镉(1 ppm)的固存显著降低,表明蓝藻种群对植物修复具有重要作用。仅1 ppm镉与1 ppm钒酸盐共处理的植物修复效果显著高于“镉+红霉素”处理(P<0.05)。在钒酸盐浓度为1 ppm的情况下,添加10 ppm柠檬酸盐比只添加1 ppm镉的情况下,Azolla-Nostoc共生对镉的修复能力显著提高(p<0.05)。我们假设柠檬酸盐要么作为“钒吸收剂”,要么作为高柠檬酸合酶的辅助因子,促进镉的修复。当使用同柠檬酸合成酶推断系统发育时,蓝藻被近似于Nostoc和Anabaena之间的分类模糊区,尽管显示出更接近Anabaena集群。本文提出,蓝藻的贡献似乎对红豆菜有效修复镉的能力至关重要,而钒酸盐依赖机制似乎提供了“援助之手”,这可能是固氮机制。研究了钒酸盐辅助植物修复与高钒生物利用度之间的关系,为开发生物解决方案提供了重要的基础。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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