微生物还原五价钒的电子传递过程及其钒还原对藻类生长的影响

为探究微生物还原五价钒[V(Ⅴ)]的机理，从钒污染土壤中筛选出一株V(Ⅴ)还原菌，经鉴定为神户肠杆菌(Enterobacter kobei NC1-2)，研究不同电子传递抑制剂和电子穿梭体对菌株NC1-2还原V(Ⅴ)的电子传递过程的影响，以及V(Ⅴ)微生物还原前后的毒性变化及其对藻类生长的影响。结果表明，当V(Ⅴ)初始浓度20 mg·L-1，培养3 d时菌株NC1-2对V(Ⅴ)的还原率为90.3%。扫描电镜(SEM)结果显示菌株表面附着无定形物质，结合能量散射X射线谱(EDS)分析证实无定形物质中含有钒元素；X射线光电子能谱(XPS)分析表明菌株NC1-2将V(Ⅴ)还原为V(Ⅳ)。电子传递抑制剂辣椒素、奎那克林和氯化铜能抑制菌株NC1-2对V(Ⅴ)的还原；核黄素作为电子穿梭体可缩短电子传递距离，促进胞外电子传递，有利于V(Ⅴ)的还原，进而加快菌株NC1-2对V(Ⅴ)的还原。V(Ⅴ)还原成V(Ⅳ)后毒性降低，减少了对小球藻Chlorella pyrenoidosa和斜生栅藻Scenedesmus obliquus的生长胁迫，两种藻生长96 h时的藻密度显著增加，且叶绿素a含量均有所提高，...

Electron transfer of microbial V(Ⅴ) reduction and its effects on algae growth

To explore the mechanism of microbial V(Ⅴ) reduction, a strain of Enterobacter kobei NC1-2 was isolated from vanadium-contaminated soil to investigate the effects of different electron transfer inhibitors and electron shuttles on the electron transfer process of V(Ⅴ) reduction, as well as the changes in toxicity before and after microbial V(Ⅴ) reduction and its effects on algal growth. The results showed that the reduction rate of V(Ⅴ) by strain NC1-2 was 90.26% after 3 d of incubation at an initial V(Ⅴ) concentration of 20 mg·L^-1. Scanning electron microscopy showed that amorphous materials were attached to the surface of the strain, which was confirmed to contain vanadium by energy-scattering X-ray spectroscopy. Additionally, X-ray photoelectron spectroscopy analysis indicated that strain NC1-2 reduced V(Ⅴ) to V(Ⅳ). Furthermore, the reduction of V(Ⅴ) by strain NC1-2 was inhibited by the electron inhibitors capsaicin, quinacrine, and copper chloride. Conversely, riboflavin, acting as an electron shuttle, shortened the electron transfer distance and promoted extracellular electron transfer, thus facilitating the reduction of V(Ⅴ) by strain NC1-2. The toxicity of V(Ⅴ)decreased after its reduction to V(Ⅳ), resulting in reduced growth stress to Chlorella pyrenoidosa and Scenedesmus obliquus. Both algal species exhibited a significant increase in algal density after 96 h of growth and in chlorophyll a content at 17.4 and 15.8 mg·L^-1, respectively. This study demonstrates that enhanced microbial reduction of V(Ⅴ) reduces its toxicity to aquatic organisms.