旱地作物根际和非根际土壤硝酸盐异化还原成铵细菌群落组成的研究

为研究典型旱地农田土壤硝酸盐异化还原成铵过程(Dissimilatory nitrate reduction to ammonium,DNRA)的群落组成,针对DNRA过程的功能基因nrfA进行高通量测序.根际和非根际、4种典型农作物共16个样品,质控后每个样品得到87000条序列,在相似度≥90%下划分到27952个OTUs,选取其中丰度较高的258个代表OTUs进行生态学分析.多样性分析(OTUs水平)结果表明:3/4的作物根际土壤样品中的DNRA群落丰富度、物种多样性和物种均匀度高于相应非根际样品,对比4种作物,粟作物根部土壤DNRA群落多样性最高,玉米作物非根际土壤最低.对代表OTUs进行分类,共定义到6个门(Phylum),19个属(Genus).其中相对丰度最高的3个属为Hyalangium(29.31%)、Chthoniobacter(20.33%)和Nitrospira(13.41%),表明三者在群落组成中占主导地位.结合土壤理化因子分析,DNRA群落相对丰度与NO~-_2-N、TN、含水率、TOM、pH及温度呈显著相关关系.本研究在一定程度上揭示了旱地农田土壤DNRA细菌的群落组成、多样性及与土壤环境因子的关系,为提高氮肥的利用效率和减小环境污染提供理论依据.     

Methylenetetrahydrofolate reductase deficiency: Prenatal diagnosis and family studies

Prenatal diagnosis of methylenetetrahydrofolate reductase (MTHFR) deficiency and family studies were performed because of a severely affected first child in this family. The fetus at risk was found to be heterozygous as confirmed by the enzymatic activity assay performed several times after birth. In the father, MTHFR activity was normal in lymphocytes and decreased in fibroblasts, whereas in the asymptomatic mother, the activity was not detectable in fibroblasts and was very low in lymphocytes. The absence of any clinical symptoms in the mother despite a clear MTHFR deficiency and hyperhomocystinemia emphasizes the heterogeneity of this disease.     

湿法脱硫中亚硫酸钙溶解特性的实验研究

亚硫酸钙的溶解浓度对氧化速率有非常重要的影响,课题主要研究CaSO3的溶解特性,描述了CaSO3在不同条件下(温度、pH、溶解时间T、搅拌速度、初始加入量等)溶解量的变化规律,进而找出CaSO3的最佳溶解条件,以达到提高氧化速率及石膏的生成率,防止堵塞和结垢的目的。     

酸雨致酸土壤对小麦幼苗若干营养代谢的影响

通过模拟酸雨淋洗土壤,造成土壤酸化和盐基流失.将小麦幼苗栽培于由酸雨致酸的土壤,其体内的碳素代谢和氮素代谢受到抑制,从而导致体内可溶性糖含量和含N量下降.其中致酸土壤对根系碳素代谢和氮素代谢的抑制作用大于对茎叶碳素代谢和氮素代谢的抑制作用.表4参23     

硝酸还原酶介导的NO合成参与SO2引发的拟南芥气孔运动的调节

以拟南芥为材料,研究了硝酸还原酶(NR)途径在植物适应SO2胁迫中的作用.结果表明:SO2胁迫可诱导4周龄拟南芥植株叶片NR活性增强、一氧化氮(NO)水平提高,NR活性和NO水平与SO2暴露时间呈正相关.NR抑制剂叠氮化钠(NaN3)可缓解SO2诱发的NO水平升高.RT-PCR检测发现,SO2熏气72 h时拟南芥NR途径关键基因Nia1、Nia2和NiR1均转录上调.研究还发现,SO2可诱发拟南芥野生型、突变体nia2、nia1nia2的气孔关闭,NaN3和NO清除剂c-PTIO可阻止SO2诱发的野生型和nia2气孔关闭,说明通过NR途径合成的NO参与了SO2胁迫诱发的拟南芥气孔运动调节.研究结果表明,NR活性的增强介导了SO2胁迫期间拟南芥叶片NO水平的升高,后者参与胁迫期间拟南芥气孔运动的调控,以增强拟南芥植株对SO2胁迫的适应性.     

稀有鮈鲫HMGR基因全长克隆及雄鱼经五氯酚暴露基因表达的分析

3-羟基-3-甲基戊二酰辅酶A还原酶(3-hydroxy-3-methylglutaryl coenzyme A reductase,HMGR)是甲羟戊酸(mevalonic acid,MVA)途径中的第一个关键限速酶.克隆稀有鮈鲫HMGR基因全长,分析该基因在不同组织及雄鱼经不同浓度五氯酚(pentachlorophenol,PCP)暴露的表达差异,探索PCP对类固醇激素前体(胆固醇)合成水平基因转录调控的内分泌干扰机制.采用同源克隆策略及cDNA末端快速扩增技术(rapid-amplification of cDNA ends,RACE),从稀有鮈鲫肝脏中首次克隆得到3 101碱基(bp)的HMGR基因cDNA全长,基因命名为GrHMGR(GenBank accession No:KF885724).GrHMGR编码884个氨基酸,系统发育树分析表明,GrHMGR编码的蛋白与其他鱼类来源的HMGR氨基酸序列同源性较高.Real-time PCR分析表明GrHMGR的表达有组织特异性,在大脑,性腺和肝脏中均有表达,性腺中表达量最高.稀有鮈鲫雄鱼经不同浓度PCP暴露后,GrHMGR在大脑和性腺的表达随PCP浓度的增加显著下降,然而在肝脏组织中表达趋势有所不同.HMGR的表达下降会减少胆固醇的合成.说明PCP暴露会通过干扰稀有鮈鲫的胆固醇合成途径,进而对内分泌系统产生影响.     

Effects of cathode potentials and nitrate concentrations on dissimilatory nitrate reductions by Pseudomonas alcaliphila in bioelectrochemical systems

The effects of cathode potentials and initial nitrate concentrations on nitrate reduction in bio- electrochemical systems （BESs） were reported. These factors could partition nitrate reduction between denitrification and dissimilatory nitrate reduction to ammonium （DNRA）. Pseudomonas alcaliphilastrain MBR utilized an electrode as the sole electron donor and nitrate as the sole electron acceptor. When the cathode potential was set from -0.3 to -I.1 V （vs. Ag/AgC1） at an initial nitrate concentration of 100 mg NO~-N/L, the DNRA electron recovery increased from （10.76 ± 1.6）% to （35.06 ± 0.99）%; the denitrification electron recovery decreased from （63.42 ± 1,32）% to （44.33 ± 1.92）%. When the initial nitrate concentration increased from （29.09 ± 0.24） to （490.97 ± 3.49） mg NO3-N/L at the same potential （-0.9 V）, denitrification electron recovery increased from （5.88 ± 1.08）% to （50.19 ±2.59）%; the DNRA electron recovery declined from （48.79 ±1.32）% to （16.02 ± 1.41）%. The prevalence of DNRA occurred at high ratios of electron donors to acceptors in the BESs and denitrification prevailed against DNRA under a lower ratio of electron donors to acceptors. These results had a potential application value of regulating the transformation of nitrate to N2 or ammonium in BESs for nitrate removal.     

异化铁还原对土壤中重金属形态转化及其有效性影响

铁的微生物还原是以Fe(Ⅲ)为末端电子受体在厌氧条件下氧化有机物的产能过程,在生物地球化学循环中起着重要的作用.铁呼吸被认为是地球上最古老的微生物代谢形式,与水体、土壤及沉积物中物质循环息息相关.铁的微生物还原对土壤中重金属形态转化有显著影响,对修复重金属及放射性核素污染的场地有着重要意义.本文综合评述了近年来铁微生物还原研究进展,从生态安全和可持续发展角度,探讨了异化铁还原对重金属的形态改变及重金属污染土壤修复的潜在价值,并对其应用前景进行客观分析.异化铁还原对重金属形态转化的影响机制,可初步归纳为异化铁还原对重金属的氧化还原作用、对重金属的甲基化作用、对重金属的固定作用,其作用机制包含生物过程和化学作用的相互穿插,值得进一步深入研究.     

Enhanced debromination of 4-bromophenol by the UV/sulfite process: Efficiency and mechanism

Halogenated aromatic compounds have attracted increasing concerns due to their toxicity and persistency in the environment, and dehalogenation is one of the promising treatment and detoxification methods. Herein, we systematically studied the debromination efficiency and mechanism of para-bromophenol(4-BP) by a recently developed UV/sulfite process. 4-BP underwent rapid degradation with the kinetics accelerated with the increasing sulfite concentration, pH(6.1–10) and temperature, whereas inhibited by dissolved oxygen and organic solvents. The apparent activation energy was estimated to be 27.8 kJ/mol. The degradation mechanism and pathways of 4-BP were explored by employing N_2O and nitrate as the electron scavengers and liquid chromatography/mass spectrometry to identify the intermediates. 4-BP degradation proceeded via at least two pathways including direct photolysis and hydrated electron-induced debromination. The contributions of both pathways were distinguished by quantifying the quantum yields of 4-BP via direct photolysis and hydrated electron production in the system. 4-BP could be readily completely debrominated with all the substituted Br released as Br-, and the degradation pathways were also proposed. This study would shed new light on the efficient dehalogenation of brominated aromatics by using the UV/sulfite process.     

闽江河口潮滩沼泽湿地沉积物铁的形态和空间分布

滨海潮滩沉积物铁异化还原过程对有机质代谢及生源要素(C、N、P、S、O等)生物地球化学循环具有深远的影响.本文以闽江河口鳝鱼滩潮滩湿地为研究对象,对高、中、低潮滩0~80 cm深度内与铁异化还原相关的不同形态铁的含量和空间分布进行分析.结果表明,无定形Fe(Ⅲ)((39.3±5.3)μmol·g~(-1))和晶质Fe(Ⅲ)((84.2±10.7)μmol·g~(-1))主要分布在高潮滩,并沿着向海方向减少;铁的硫化物FeS((15.3±2.8)μmol·g~(-1))和Fe S2((6.0±1.1)μmol·g~(-1))集中分布在中、低潮滩;非硫Fe(II)((111.7±12.8)μmol·g~(-1))富集在整个潮滩剖面上,且含量随着深度增加而增加.孔隙水Fe~(2+)((3.7±0.7)mmol·L~(-1))与Fe S2、SO_4~(2-)和pH相关,说明Fe~(2+)可能与黄铁矿的水解有关.不同形态铁在高、中、低潮滩表现出显著的空间分布异质性.高潮滩铁异化还原的强度大于硫酸盐异化还原,但沿着向海方向,硫酸盐异化还原的潜势逐渐增加.本研究证明了潮汐水文和高程对潮滩湿地铁的迁移和转化具有重要的意义.