绿地再生水灌溉土壤微生物量碳及酶活性效应研究

再生水灌溉引起了土壤理化性质的变化,其对土壤生物活性的影响备受关注.以再生水利用较典型的北京为研究区,分层采集了不同再生水灌溉历史的城区公园绿地与城郊农田表层土壤样品,测定并分析了一些常规理化指标、土壤微生物量碳及5种土壤酶（脲酶、碱性磷酸酶、蔗糖酶、脱氢酶和过氧化氢酶）活性,探讨长期再生水灌溉下土壤微生物量碳和酶活性的变化.结果表明,再生水灌溉下公园绿地土壤微生物量碳和酶活性均高于其自来水对照灌区,农田上升不明显.与对照相比,公园绿地与农田再生水灌区0～20 cm土层土壤微生物量碳平均含量分别上升了60.1%和14.2%,公园绿地再生水灌区0～20 cm土层中土壤酶活性平均增幅为36.7%,而农田为7.4%.调查区土壤微生物量碳及酶活性均随土壤深度的增加而降低,其中公园绿地0～10 cm与10～20 cm土层间差异极显著.因此,北京地区城市绿地使用再生水长期灌溉有助于提高土壤生物活性.     

重金属Zn和Cd对翅碱蓬生长及抗氧化酶系统的影响

通过测定翅碱蓬生长和生理指标,研究了不同含量Zn和Cd对翅碱蓬的发芽率、苗高、苗重、体内超氧阴离子自由基(O-2)、过氧化氢(H2O2)的产生及对抗氧化酶(超氧化物歧化酶SOD、过氧化氢酶CAT、过氧化物酶POD)活性的影响,以探讨盐生植物翅碱蓬对重金属胁迫的反应.结果表明,两种重金属均不同程度地加快了超氧阴离子自由基的产生速率;翅碱蓬对Zn胁迫的耐受阈值为100 mg·kg-1,Zn含量低于100 mg·kg-1时,发芽率和苗高、苗重保持良好;含量高于100 mg·kg-1实验组,翅碱蓬生长及体内酶活性机制受到不同程度抑制,SOD 、POD反应迅速,CAT相对缓慢.翅碱蓬对Cd污染抵御能力差,含量高于0.4 mg·kg-l即可造成严重伤害,阻碍翅碱蓬生长,降低抗氧化酶活性.Zn和Cd共同作用(200 mg·kg-1 +0.2 mg·kg-1)时,表现为协同作用,发芽率仅为对照组的50.5％、苗重仅为49.2％,实验50 d后,SOD、CAT均失活,影响极显著.     

磺胺甲噁唑对猪粪堆肥过程中堆料性质与酶活性的影响

以猪粪、小麦秸秆为材料,研究了磺胺甲噁唑（SMZ）对高温堆肥过程中理化性质（温度、pH值、E₄/E₆）和酶活性（纤维素酶、磷酸酶、脲酶、多酚氧化酶）的影响.结果表明：SMZ对堆肥理化性质的影响与其浓度有关.高浓度（95 mg·kg^-1）SMZ会对微生物活性产生显著抑制作用,表现出堆肥温度难以达到无害化标准,堆料pH值较低（<9.0）.但高浓度（95 mg·kg^-1）SMZ能激活多酚氧化酶活性,且水提浸液E₄/E₆值较低.在堆肥过程中,SMZ对纤维素酶和脲酶活性呈现出“抑制-激活-抑制”的作用,50 mg·kg^-1的SMZ对纤维素酶产生不同程度的激活作用.相比之下,脲酶活性对SMZ的敏感性比纤维素酶更敏感,5 mg·kg^-1的SMZ即能显著抑制脲酶活性,中浓度（50 mg·kg^-1）的SMZ对碱性磷酸酶活性产生了显著的抑制作用.综上,SMZ通过影响酶活性而影响堆肥过程的物质转化.此外,SMZ浓度越大,种子发芽指数越低.当SMZ≥50 mg·kg^-1时,堆肥难以腐熟而对植物毒性较大.     

Overexpression of NADH oxidase gene from Deinococcus geothermalis in Escherichia coli

When using stable enzyme genes from a thermophile to create a biosensor in Escherichia coli, it is vital that these genes be overexpressed in order to provide a sufficient supply of enzymes. In this study, overexpression of the NADH oxidase (Nox) gene from the thermophile Deinococcus geothermalis was successfully achieved with the aim of creating a stable biosensor active at room temperatures. To do so, modification of 10 nucleotides, GAAATTAACT, upstream of the start codon of the Nox gene was necessary.     

Overexpression of NADH oxidase gene from Deinococcus geothermalis in Escherichia coli

When using stable enzyme genes from a thermophile to create a biosensor in Escherichia coli, it is vital that these genes be overexpressed in order to provide a sufficient supply of enzymes. In this study, overexpression of the NADH oxidase (Nox) gene from the thermophile Deinococcus geothermalis was successfully achieved with the aim of creating a stable biosensor active at room temperatures. To do so, modification of 10 nucleotides, GAAATTAACT, upstream of the start codon of the Nox gene was necessary.     

Soil microbial community structure and function responses to successive planting of Eucalyptus

Many studies have shown soil degradation after the conversion of native forests to exotic Eucalyptus plantations. However, few studies have investigated the long-term impacts of short-rotation forestry practices on soil microorganisms. The impacts of Eucalyptus successive rotations on soil microbial communities were evaluated by comparing phospholipid fatty acid （PLFA） abundances, compositions, and enzyme activities of native Pinus massoniana plantations and adjacent 1st, 2nd, 3rd, 4th generation Eucalyptus plantations. The conversion from P. massoniana to Eucalyptus plantations significantly decreased soil microbial community size and enzyme activities, and increased microbial physiological stress. However, the PLFA abundances formed ＂U＂ shaped quadratic functions with Eucalyptus plantation age. Alternatively, physiological stress biomarkers, the ratios of monounsaturated to saturated fatty acid and Gram＋ to Gram- bacteria, formed ＂∩＂ shaped quadratic functions, and the ratio of cy17：0 to 16： 1ω7c decreased with plantation age. The activities of phenol oxidase, peroxidase, and acid phosphatase increased with Eucalyptus plantation age, while the cellobiobydrolase activity formed ＂U＂ shaped quadratic functions. Soil N：P, alkaline hydrolytic nitrogen, soil organic carbon, and understory cover largely explained the variation in PLFA profiles while soil N：P, alkaline hydrolytic nitrogen, and understory cover explained most of the variability in enzyme activity. In conclusion, soil microbial structure and function under Eucalyptus plantations were strongly impacted by plantation age. Most of the changes could be explained by altered soil resource availability and understory cover associated with successive planting of Eucalyptus. Our results highlight the importance of plantation age for assessing the impacts of plantation conversion as well as the importance of reducing disturbance for plantation management.     

丛枝菌对转Bt基因棉根际土壤营养物质及酶活性的影响

转Bt基因抗虫棉已在全球范围内广泛种植,然而Bt棉根际分泌物是否会影响土壤理化性质及土壤功能尚缺乏深入研究。通过盆栽实验方法,设计不同的棉花品种与是否接种丛枝菌总共4个处理,以此研究Bt棉和接种丛枝菌根真菌对植物根际土壤营养物质含量以及土壤酶活性的影响。结果显示:丛枝菌可以使non-Bt棉和Bt棉根际土壤营养物质中的土壤有机质和土壤总氮含量显著增加,但是对根际土壤全磷却鲜有影响。转基因对于不同品种棉花根际土壤酶,丛枝菌均能有效增强其活性。由此表明,丛枝菌对Bt棉和non-Br棉根际土壤环境均具有改善作用。     

利用泰乐菌素菌渣生产复合酶制剂及效果研究

发酵法生产抗生素过程中会产生大量废弃菌渣,这些菌渣因有机质含量高,堆放极易发生霉变,给当地环境造成危害.文章采用固体发酵法,以微生物降解处理后的泰乐菌素菌渣为主要原料,生产复合酶制剂,并对其在肉鸡上的使用效果进行研究.结果表明:在水含量50％～60％、干物质中麸皮含量不低于40％的泰乐菌素菌渣培养基中,接入5％～10％...     

中亚热带马尾松林凋落物分解过程中的微生物与酶活性动态

采用凋落物原位分解法,研究了中亚热带马尾松林中马尾松、槲栎凋落叶单独及混合(自然质量比8∶2)分解过程中的微生物数量与酶活性动态.结果表明:①3类凋落物的年分解常数K的大小为:混合凋落物(0.94)>槲栎凋落物(0.86)>马尾松凋落物(0.67);②3类凋落物真菌数量和微生物数量均在夏季(135 d时)达到最大值,而此时细菌和放线菌数量最低;③3类凋落物纤维素酶活性、酸性磷酸酶活性均与凋落物干重剩余率呈显著正相关(P<0.05),而马尾松与混合型凋落物中的多酚氧化酶活性同凋落物干重剩余率呈极显著负相关(P<0.01);④微生物数量和多酚氧化酶活性均总体表现为槲栎凋落物>混合凋落物>马尾松凋落物,酸性磷酸酶活性多表现为槲栎凋落物最低,与分解常数K排列有一定的差异,说明凋落物分解是微生物和多种酶共同作用的结果.整体研究表明,凋落物质量和季节气候的差异显著影响微生物群落及其调控的生态过程,与纯马尾松凋落叶相比,针阔混合使微生物数量和多酚氧化酶活性显著提高,这可能是导致分解加快的重要原因.