Research progress on occurrence forms and microbial transformation of mercury北大核心CSCD

汞是一种高毒性且具有持久性的重金属污染物,汞污染的治理与修复在近几十年一直是国内外研究热点.了解微生物对汞赋存形态的转化作用,对汞污染的治理与修复具有重要意义.总结汞的不同赋存形态、毒性及对应的常用分析方法,其中甲基汞(methyl mercury,MeHg)是毒性最强的汞形态之一.环境中汞的化学形态能发生转化,尤其以微生物驱动的汞的甲基化、MeHg的去甲基化和汞的氧化还原最为常见.依据汞转化类型将汞转化相关微生物分为汞甲基化、MeHg去甲基化、汞还原、汞氧化等类群,将对应的汞转化作用机制分为基于hgcAB基因的汞甲基化、基于mer操纵子基因的MeHg去甲基化和Hg2+还原、胞内过氧化氢酶介导的Hg0氧化.微生物汞转化过程不仅受到pH和温度的显著影响,而且还受到汞的赋存形态和游离汞的浓度、微生物种/群结构与功能、矿物种类、中间体和次生产物及其交互作用的影响,基于此,提出正确客观表征汞的微生物转化过程需要综合分析微生物组和矿物组的变化规律及其交互作用的综合效应.针对酸性矿山废水(AMD)极端环境微生物汞转化研究的不足,未来的工作将聚焦结合多组学手段、同步辐射谱学和密度泛函理论(DFT)计算等分析技术研究汞赋存形态的微生物转化过程,分析和阐明汞转化中间体的键合作用方式和转化机制,从而为AMD汞污染的预防、治理和修复提供依据.(图2表2参107)     

Effects of photoperiod on photosynthetic characteristics and quality of Tetragonia tetragonoides (Pall.) Kuntze in a plant factory北大核心CSCD

为探究光周期对番杏[Tetragonia tetragonoides(Pall.)Kuntze]生长及品质的影响,利用植物工厂中光源高度可控的优势对番杏进行不同光照时间(8、10、12、14、16 h)处理,测定分析番杏的生长、光合特性及营养品质.结果表明:(1)番杏各农艺性状随光照时间延长而增长,在光照时间14 h与16 h处理之间未呈显著性差异(P<0.05);(2)适宜光周期有利于光合色素积累,在16 h处理下叶绿素a、总叶绿素和类胡萝卜素含量最大,叶绿素b含量则在14 h光照时最大;净光合速率(P_(n))、蒸腾速率(T_(r))和气孔导度(G_(s))随光照时间延长上升,其中净光合速率在14 h与16 h光照之间变化不显著,胞间CO_(2)(C_(i))则呈先降后升的趋势;光周期变化对最大光化学效率F_(v)/F_(m)与光化学淬灭系数q_(P)未造成显著影响,非光化学淬灭系数NPQ随光照时间延长呈先降后升的趋势,14-16 h光照处理之间变化不显著,电子传递效率ETR则随光周期延长而降低;(3)不同光周期对番杏各营养成分含量的影响有所差异,可溶性蛋白变化差异较小,硝酸盐随光照时间延长而降低,14 h光照下可溶性糖含量最大.本研究表明14-16 h光照处理有利于番杏生长和营养物质积累.(图5表2参37)     

Enhancement of MK-7 synthesis by engineered strains of Bacillus subtilis natto that overexpress men genes and by increasing available dissolved oxygen北大核心CSCD

In recent years, researchers have discovered novel physiological functions of vitamin K2. In addition to promoting blood clotting, it can prevent osteoporosis and cardiovascular disease and is expected to treat some tumors and Parkinson’s disease. Bacillus subtilis natto is a probiotic that has been approved by the U.S. Food and Drug Administration for use as a bioproducer of vitamin K2. Its product’s main form is MK-7, which has a long half-life in the human body and high bioavailability. Bacillus subtilis natto displays great potential for large-scale biological preparation of vitamin K2. In this study, the Sipizizen method of Bacillus subtilis transformation was optimized to make it suitable for molecular transformation of Bacillus subtilis natto. Vectors for overexpression of all 8 genes involved in the menadione synthetic pathway were constructed, and changes in MK-7 fermentation yield after transformation of Bacillus subtilis natto were investigated. Three enzymes were found to exert significant effects on MK-7 synthesis, namely isopentenyltransferase (MenA), 1,4-dihydroxy-2-naphthoyl-CoA synthase (MenB), and nornaphthoquinone methyltransferase (MenG). A modified strain (BN-pABG) with higher MK-7 productivity was obtained by concerted overexpression of menA, menB, and menG. In a 5 L bioreactor, MK-7 synthesis was further enhanced by optimizing oxygen supply. The final yield of MK-7 from the modified strain was 62.21 mg/L, 1.26 times higher than that of the original strain. These results show that combined overexpression of menA, menB, and menG strongly promotes MK-7 synthesis by Bacillus subtilis natto, and optimizing the oxygen supply conditions also promotes more robust MK-7 synthesis. © 2022 Authors. All rights reserved.     

The diversity and floristic characteristics of mosses in Jiuzhaigou National Nature Reserve北大核心CSCD

苔藓是生态系统的重要组分和自然保护区的重点保护对象之一,在物种资源和生态系统功能维护中具有重要作用.通过野外标本采集和室内鉴定,对九寨沟国家级自然保护区的藓类植物的物种组成和分布特点进行研究.结果表明:(1)九寨沟共有藓类植物38科90属211种(含变种),其中优势科为青藓科(Brachytheciaceae)、丛藓科(Pottiaceae)、灰藓科(Hypnaceae)、金灰藓科(Pylaisiaceae)、提灯藓科(Mniaceae)、真藓科(Bryaceae)和羽藓科(Thuidiaceae);并且调查发现两种濒危级别的珍稀藓种.(2)九寨沟藓类植物的区系地理成分可划分为10个,优势成分为东亚分布,占34.2%,其次为北温带分布,占30.9%.(3)通过与西南地区5个自然保护区藓类植物的相似系数和区系谱主成分分析发现,九寨沟藓类植物种类与贡嘎山的共有种最多,达到94种,在区系成分上也与贡嘎山和王朗相近.本研究表明九寨沟高原喀斯特生境藓类植物物种资源丰富,虽然区系地理成分具有多样和复杂性,但主要还是以东亚分布和温带分布为主,在物种相似度和区系成分上与贡嘎山和王朗的藓类植物一致性更高.(图3表6参47)     

Elucidation of adsorption mechanisms and mass transfer controlling resistances during single and binary adsorption of caffeic and chlorogenic acids

Environmental Science and Pollution Research - In this work, the potential of activated carbon to remove caffeic and chlorogenic acids in aqueous solution was investigated. The study focused on...     

Use of Seawater in Flue Gas Desulfurization

For seasite power plants using seawater for condenser cooling, Bechtel developed a new process to remove better than 90 percent of flue gas SO₂ using seawater and lime. Tests demonstrate that marine life is not affected by the effluent from this unique scrubbing process; therefore, the aqueous effluent containing reacted products (gypsum) in solution at low concentration is suitable for discharge to the sea.     

Overview of the impact of noninvasive prenatal testing on diagnostic procedures

Noninvasive prenatal testing (NIPT) has had a profound influence in the field of prenatal diagnosis since the 1997 discovery of cell-free fetal DNA in maternal blood. Research has progressed rapidly, with clinical data supporting laboratory studies showing that NIPT is highly sensitive and specific for fetal aneuploidy, resulting in marked uptake in the high-risk patient population. The superior accuracy of NIPT compared with conventional screening methods has led to significant decreases in the number of invasive diagnostic procedures, in addition to a concomitant decrease in the number of procedure-related fetal losses. Yet, NIPT has been described as a ‘disruptive innovation’ due to the considerable changes the technology has commanded on current prenatal screening and diagnostic practices. This review summarizes both institutional and global experience with NIPT uptake, its effect on reducing diagnostic invasive procedures, and the unique challenges that reduced procedural volume may have on physician and trainee proficiency, cytogenetic laboratories, and neonatal outcome. © 2015 John Wiley & Sons, Ltd.