School of Metallurgy and Environment, Central South University, Changsha, Hunan 410083, China.
School of Minerals Processing and Bioengineering, Central South University, Changsha, Hunan 410083, China.
J Environ Manage. 2022 Dec 1;323:116173. doi: 10.1016/j.jenvman.2022.116173. Epub 2022 Sep 14.
Fungus-algae symbiotic systems (FASS) are typically used to assist in the immobilization of algae and strengthen the adsorption of heavy metals. However, the adsorption behavior of the symbiotic system and the molecular regulation mechanism of extracellular proteins in the adsorption of heavy metals have not been reported in detail. In this study, a stable FCSS (fungus-cyanobacterium symbiotic system) was used to study Cd(II) adsorption behavior. The fixation efficiency of fungus to cyanobacterium reached more than 95% at pH7.0, 30 °C, 150 rpm, and a medium ratio of 100%. The biomass, chlorophyll content, and total fatty acid content of the symbiotic system were much higher than those of cyanobacterium and fungus alone. The photosynthetic fluorescence parameters showed that the presence of fungus enhanced the light tolerance of cyanobacterium. The original light energy conversion efficiency and potential activity of PSII were enhanced, indicating that symbiosis could promote the photosynthetic process of cyanobacterium. The Cd(II) adsorption efficiency can achieve 90%. The system maintained excellent adsorption after six adsorption cycles. Differential proteins were mainly enriched in areas such as metabolism, ABC transport system, and pressure response. Cd(II) stress promotes an increase in efflux proteins. Moreover, cadmium can be fixed as much as possible by secreting extracellular proteins, and the toxicity of cadmium to cells can be alleviated by regulating the metabolism of glutathione, reducing oxidative phosphorylation level, and reducing oxidative stress, thus improving the resistance to Cd(II). Meanwhile, the expression of enzymes involved in glycolysis and the pentose phosphate pathway was upregulated, while the expression of those in the TCA cycle was downregulated. The expression of substances related to PSI and PSII in the photosynthetic system and rubisco, a key enzyme in the Calvin cycle, was significantly upregulated, indicating that the glucose metabolism and photosynthetic pathways of the symbiotic system were involved in resistance to Cd toxicity. This revealed the response mechanism of the fungus-algal symbiotic system in the process of Cd adsorption, and also provided reference value for industrial application in water treatment.
菌-藻共生系统（FASS）通常用于辅助藻类固定和增强重金属吸附。然而，共生系统的吸附行为以及胞外蛋白在重金属吸附中的分子调控机制尚未详细报道。本研究采用稳定的 FCSS（真菌-蓝藻共生系统）研究了 Cd(II)的吸附行为。在 pH7.0、30°C、150rpm 和培养基比例为 100%的条件下，真菌对蓝藻的固定效率超过 95%。共生系统的生物量、叶绿素含量和总脂肪酸含量均明显高于蓝藻和真菌单独存在时的含量。光合荧光参数表明，真菌的存在增强了蓝藻的耐光性。原初光能转换效率和 PSII 的潜在活性得到提高，表明共生可以促进蓝藻的光合作用。Cd(II)的吸附效率可达 90%。该系统在六次吸附循环后仍保持良好的吸附性能。差异蛋白主要富集在代谢、ABC 转运系统和压力响应等区域。Cd(II)胁迫会促进外排蛋白的增加。此外，通过分泌胞外蛋白尽可能地固定镉，调节谷胱甘肽代谢、降低氧化磷酸化水平和减少氧化应激，从而减轻镉对细胞的毒性，从而提高对 Cd(II)的抗性。同时，糖酵解和戊糖磷酸途径相关酶的表达上调，而三羧酸循环（TCA）相关酶的表达下调。光合系统中与 PSI 和 PSII 相关的物质以及 Calvin 循环中的关键酶 rubisco 的表达显著上调，表明共生系统的葡萄糖代谢和光合途径参与了对 Cd 毒性的抗性。这揭示了真菌-藻共生系统在 Cd 吸附过程中的响应机制，也为水处理工业应用提供了参考价值。
