西瓜汁的高强度脉冲磁场杀菌试验研究及杀菌机理分析

该文旨在研究液态食品的高强度脉冲磁场杀菌技术，探讨高强度脉冲磁场对微生物细胞产生的生物效应。以西瓜汁的杀菌为例，研究了磁场强度和脉冲数对杀菌效果的影响。研究结果表明：随着场强和脉冲数的增加，从整体上讲杀菌效果增强；在场强为2.53 T、脉冲数为20时，杀菌效果最好。当脉冲数为40时，磁场强度对杀菌效果的影响为单调增加；当磁场强度为4.22 T时，脉冲数对杀菌效果的影响为单调增加。但在某些参数下杀菌效果出现反弹现象，其原因有待进一步探讨。从脉冲磁场导致细胞跨膜电位、感应电流、带电粒子洛仑兹力、离子能量等参数变化的角度，描述了脉冲磁场对微生物细胞产生的生物学效应，分析了致使细胞结构被破坏、正常生理活动受阻碍的机理。     

天台山不同林型土壤微生物DNA总量的分布特性

研究了天台山8种植被类型土壤微生物DNA总量分布的特性及其与土壤微生物数量、土壤生化活性和土壤其它环境因素之间的关系。土壤的发育程度等对土壤微生物DNA总量分布影响较大。此外,土壤微生物数量、微生物生物量C和土壤呼吸速率对土壤微生物DNA总量分布的直接作用和它门之间的相互作用产生的间接影响较显著。在所测的8种土壤理化因素中,土壤微生物DNA总量分布对土壤pH、有机质、全氮、全磷、全钾影响较大。     

一种土壤微生物总DNA的高效提取方法

获得高浓度、大片段、多样性程度高的土壤微生物总DNA 是研究土壤微生物群落结构的分子生态学基础。本文采用间接法(菌体细胞回收法)提取红壤地区两种土壤类型的土壤微生物总DNA,定量计算其回收率,并与直接法(细胞原位裂解法)比较了提取效率和纯度。结果表明:红壤地区2种土壤每克干土的总DNA提取量,间接法约为0.34和0.53礸/g干土,直接法约为13.62和24.32礸/g干土;间接法的提取效率低于直接法,但所得DNA片段较大,且Sau 3AⅠ 酶切和16 S rDNA通用引物PCR扩增结果显示,间接法比直接法更能有效地去除土壤中的某些抑制剂,所得总DNA的纯度更高,有利于后续操作。     

高压脉冲电场对酿酒酵母钝化机理研究

为探究高压脉冲电场（PEF）对微生物的钝化机理,该试验主要采用Lowry法、SDS-PAGE电泳、APIZYM试剂盒、流式细胞仪等方法测定PEF处理对酿酒酵母蛋白质含量、胞内酶活性和DNA等的影响。结果显示：PEF处理后,酿酒酵母胞内蛋白质含量显著降低（p<0.05）,SDS-PAGE 电泳图分析发现酿酒酵母胞内蛋白谱图不清晰,且有小分子和 60 KDa 以上大分子蛋白谱带缺失,酿酒酵母细胞内13种酶的活性均有不同程度的下降,细胞DNA含量降低,部分DNA变性。PEF钝化微生物与其胞内酶失活、蛋白质和DNA发生外泄或变性有关。     

高压脉冲电场对酿酒酵母蛋白质及DNA的影响

为探究高压脉冲电场（PEF）对微生物的钝化机理,本实验主要采用Lowry法、SDS-PAGE电泳、APIZYM试剂盒、流式细胞仪等方法测定PEF处理对酿酒酵母蛋白质含量、胞内酶活性和DNA等的影响。结果显示：PEF处理后,酿酒酵母胞内蛋白质含量显著降低(p<0.05),SDS-PAGE 电泳图分析发现酿酒酵母胞内蛋白谱图不清晰,且有小分子和 60 KDa 以上大分子蛋白谱带缺失,酿酒酵母细胞内 13 种酶的活性均有不同程度的下降,细胞DNA含量降低,部分DNA变性。结论：PEF钝化微生物与其胞内酶失活、蛋白质和DNA发生外泄或变性有关。     

猪粪和土壤样品中微生物DNA提取方法的比较

猪粪施于土壤可能会对土壤微生物多样性造成影响，为选用同一种DNA提取方法用于土壤和猪粪微生物DNA的提取，该文采用了化学裂解法和试剂盒法同时从土壤和猪粪样品中提取微生物DNA，并对这两种方法的提取DNA的效果进行了比较。结果表明，试剂盒法不能用于提取土壤中的微生物DNA；可以从猪粪中提取到DNA，PCR扩增能得到目的产物，但重复性不高。化学裂解法提取的土壤微生物DNA浓度高但纯度低，纯化后纯度增加，但DNA有所损失，用于PCR扩增时结果不理想；处理猪粪样品，提取的DNA浓度较低但纯度较高，PCR扩增结果比较理想。由此可见，化学裂解法用来提取猪粪样品中的微生物DNA是可行的，但需寻求更好的土壤样品微生物DNA的提取方法。     

棕壤微生物和几种酶活性的磁致效应研究

试验通过室内模拟方法,研究了不同磁场强度处理棕壤后对土壤微生物数量和几种酶活性的影响。结果表明磁场对微生物数量有影响,但因磁场强度和微生物种类的不同而异。100、500mT场强对细菌表现为抑制作用,但对放线菌、真菌表现为激活作用;300mT场强对各类群土壤微生物均表现为正效应。经磁场处理后的棕壤,过氧化氢酶、过氧化物酶和三种磷酸酶活性均有不同程度的提高;随着培养时间的延长,磁致效应也发生动态变化。在磁场处理后的1～7d,其细菌、放线菌、真菌的磁致效应均显著,并出现最大值,而后随培养时间的延长逐渐变小,直至培养结束,磁场对其已无显著影响。而土壤中几种酶的磁致效应持续时间较长。     

交变磁场下磁纳米流冷却液强化柴油机缸盖微区域冷却

为能实现柴油机缸盖鼻梁微区域高效冷却兼顾节能化的要求,该文提出了一种通过外部施加交变磁场的方式促进磁纳米流内粒子的微运动达到强化传热的方法,并与传统乙二醇冷却液、Cu-乙二醇纳米流冷却液进行了柴油机缸盖鼻梁微区域传热效果的对比研究。结果表明:在0.17 Hz的磁场交变频率影响下,磁纳米流中加热棒温度值最大下降幅度提升了29.3%,内部粒子运动涡数增加。缸盖鼻梁微区域试验表明:相比传统乙二醇冷却液,稳态工况下,最大扭矩工况点和标定工况点处测点温度值最大下降幅度分别约为12%、14.4%,外特性工况下测点平均温度值降幅为23.7℃,约为9.4%。瞬态工况测试结果表明,采用交变磁场影响下的磁纳米流冷却液,柴油机预热时间较采用传统乙二醇冷却液和Cu-乙二醇纳米流冷却液分别缩短了9.8%和8.2%,柴油机急加速工况下能保持冷却液温度波动性小。能耗率计算结果表明,采用外部施加交变磁场加强磁纳米流冷却液高效传热的方式在达到相同冷却液温度时,可实现节能幅度为7.2%。该研究为柴油机乃至其他高温部件的节能化高效冷却提供科学参考。     

猪粪和土壤样品中微生物DNA提取方法的比较

猪粪施于土壤可能会对土壤微生物多样性造成影响,为选用同一种DNA提取方法用于土壤和猪粪微生物DNA的提取,该文采用了化学裂解法和试剂盒法同时从土壤和猪粪样品中提取微生物DNA,并对这两种方法的提取DNA的效果进行了比较。结果表明,试剂盒法不能用于提取土壤中的微生物DNA;可以从猪粪中提取到DNA,PCR扩增能得到目的产物,但重复性不高。化学裂解法提取的土壤微生物DNA浓度高但纯度低,纯化后纯度增加,但DNA有所损失,用于PCR扩增时结果不理想;处理猪粪样品,提取的DNA浓度较低但纯度较高,PCR扩增结果比较理想。由此可见,化学裂解法用来提取猪粪样品中的微生物DNA是可行的,但需寻求更好的土壤样品微生物DNA的提取方法。     

土壤微生物总DNA提取方法的比较

采用4种土壤DNA提取方法提取了5种类型土壤的微生物总DNA，并对4种提取方法的DNA提取效果进行综合分析，进一步通过PCR—DGGE扩增提取DNA中的细菌16S rDNA片段，并对扩增产物进行DGGE电泳分析。结果表明，SDS-高盐缓冲液法抽提的DNA得率最高，SDS-酚氯仿抽提法的DNA得率最低。DNA的纯度，以BIO-101 DNA Extraction Kit试剂盒法最高，改进试剂盒法纯度最低。通过PCR-DGGE分析土壤微生物多样性结果表明，BIO-101 DNA Extraction Kit试剂盒法提取的DNA代表的微生物多样性最全，而SDS酚氯仿法抽提的DNA代表性最差。     

Degradation of a herbicide,Beflubutamid, in upland soils and isolation of its degrading microbes

Abstract

To clarify the degrading mechanisms of a newly synthesized herbicide, Beflubutamid ([RS]-N-benzyl-2-[4-fluoro-3-trifluoromethylphenoxy]butanamide; BFB), in soil, we started a series of studies. The results on the characteristics of degradation in soil, and on the isolation and identification of BFB-degrading microbes are summarized as follows. BFB was immediately degraded in non-sterilized soil, but degraded little in sterilized soil, indicating that soil microbes are involved in BFB degradation in soil. Results suggested that the application of sawdust and cattle manure (CM) increased the population and activities of microbes because the degrading activity was greater in CM-applied soil than in soil supplied with chemical fertilizer. According to the morphological characteristics and 18S rDNA sequences, the isolated strain MF1 was categorized as the class Ascomycota, belonging to the order Hypocleales, and closely related to Gibberella fujikuroi, Fusarium oxysporum f. sp. Vasinfeatum and Gibberella puricaris. The results suggested that BFB degrades fastest under acidic conditions because the growth of strain MF1 was at an optimum at pH 6.5 and was depressed at neutral and alkaline pHs.     

Leaf structure and chemical compositions are correlated with cotton boron efficiency

In this study, in order to investigate the boron (B) efficiency and response to changes in leaves structure and chemical compositions correlated with B efficiency, two different cotton genotypes including genotype 103 and genotype 122 were treated by B-deficiency (0 mg L^?1) or moderate B (0.2 mg L^?1). All the seedlings were grown in hydroponics situation with modified Hoagland and Arnon solution under greenhouse conditions for 6 weeks. The changes in chemical compositions and cell structure of leaves as a consequence of B deficiency were revealed by Fourier-transform infrared spectroscopy (FTIR), ¹³C nuclear magnetic resonance (¹³C-NMR) and transmission electron microscope (TEM). The results showed that the leaves of genotype 122 appeared crinkled and prolapsed having more obvious symptoms than genotype 103. Besides, the dry mass of every part was higher while B concentration was lower in genotype 103, indicating that genotype 103 was much tolerant to low B, which was related to higher B utilization efficiency of genotype 103 under B-deprived condition. In addition, B deficiency stunted the synthesis of proteins, carbohydrates, cellulose and lignin, which is noticed more seriously in leaves of genotype 122, and the structure and integrity of cells were significantly destroyed by B starvation. These results indicated that genotype 103 had higher B efficiency than genotype 122, and the changes in the chemical composition and cell structure might be either specific or adaptive responses to B efficiency.     

香根草光合特性对水淹-干旱交替胁迫的响应

三峡水库消落带因水位的周期性变化,使其土壤含水量呈干湿交替变化,而大多数原有植物难以适应新的生境,导致生态系统严重破坏。利用盆栽法模拟其水淹条件,以30,60,90和120d为周期进行水淹—干旱交替处理,研究了香根草当年实生幼苗在水淹与干旱交替胁迫下的光合特性及生理生态适应机制。结果表明,不同胁迫周期的水淹—干旱交替胁迫均显著影响香根草幼苗的生长及其光合生理特性。各组幼苗的株高、净光合速率、气孔导度及叶绿素含量等生理生态学指标均随时间变化呈不同幅度的升降变化。而不同组间的各项指标值均随交替周期的增大而减小。但无论何种变化,各处理组最终又都能逐渐恢复或趋于稳定状态,保持较高的存活率。因此,香根草对水淹和干旱均具有良好的耐受力和适应性,可作为三峡库区消落带植被恢复建设的重要植物种类。     

水淹条件下水稻土中砷的生物化学行为研究进展

水稻土中砷的氧化还原和甲基化等生物化学过程是影响水稻砷毒性的主要作用机制;同时,水淹厌氧条件是驱动水稻土中砷的生物化学过程关键环节,且是导致水稻对砷大量吸收累积的主要原因,对以水稻为主食的人们造成健康威胁。本文综述了水稻土中砷的氧化还原和甲基化现象、砷的生物化学作用机制以及影响水稻土砷迁移转化的关键因素,并探讨了水淹厌氧条件对水稻土砷代谢微生物群落、微生物基因表达水平以及对砷归趋的影响。最后,展望了未来的研究方向,以期识别不同水管理模式下土壤微环境对水稻土中砷代谢微生物群落结构与基因表达水平的影响机制,为深入理解砷的生物化学行为和降低水稻对砷的吸收累积提供科学的理论参考。     

Seasonal variations and effects of nutrient applications on N and P and microbial biomass under two temperate heathland plants

Eutrofication is a threat against nutrient-poor habitats as increased amounts of nutrients in ecosystems may cause changes in the vegetation. Nitrogen (N) deposition leads to conversion of Calluna heathlands into graminoid dominated heath, but low availability of P may hinder or slow down this process.In this study the soil properties under two dominant heathland plants, the dwarf shrub Calluna vulgaris and the grass Deschampsia flexuosa, were investigated, with focus on nutrient content in the organic top soil and soil microbes during the main growing season and effects of nutrient amendments. The concentration of inorganic and dissolved organic N was significantly higher under D. flexuosa than C. vulgaris all though there were the same amounts of total N in the soil below the two species. N and P amendment enhanced available N and P in the soil, but added nutrients had little direct effects on microbes. The microbial biomass on the other hand was positively related to soil water content in fertilized plots indicating that this was due to an indirect effect of enhanced nutrient availability. Microbial N and P pools were respectively 1000 and 100 times higher than the pool of inorganic N and P, and microbes therefore may play an important role in regulating plant nutrient supply. Judged from responses of inorganic and microbial N and P concentrations to added N and P, N seemed to limit C. vulgaris and soil microbes below while P seemed to limit D. flexuosa and soil microbes below this species. There were lower rates of net nitrification, net ammonification and DOC and DON production rates during winter in the soil under C. vulgaris than below D. flexuosa, although all these rates were equal under the two species on an annual basis. This indicates that these microbial processes were taking place during winter but were affected by exudates from C. vulgaris.     

Coupled magnetic nanoparticle-mediated isolation and single-cell image recognition to detect Bacillus' cell size in soil

Microbial morphology fundamentally constrains how species interact with their environment, and hence ultimately affects their niche. However, the methodology of functional microbes in the soil ecosystem is still poorly studied since it is difficult to capture and identify the active monospecific community from the complicated environment and enormous number of microbial species in soils. To comprehensively reveal the morphology of active microbes in soil ecosystem, magnetic nanoparticle-mediated isolation (MMI) and single-cell image recognition (SCIR) were employed to study soil active Bacillus community, which functionally boosted the soil fertility in organic fertilisation compared to mineral fertilisation and unfertilised control treatments in our previous study. The results showed that MMI and SCIR can efficiently isolate active Bacillus from soil particles and other microorganisms. High throughput sequencing showed that the captured Bacillus showed similar community structure in different long-term fertilisation soils, while SCIR revealed that the active Bacillus was greater in number and larger in size in organic fertilisation treatment compared to mineral fertilisation and unfertilised control treatments. Our study demonstrates that the combination of MMI and SCIR is a potentially powerful tool to capture and identify the morphology of active and functional microbes in the soil ecosystem.     

规模化稻鸭生态种养对稻田杂草群落组成及物种多样性的影响

为探索规模稻鸭生态种养稻田杂草群落的变化动态,运用植物群落生态的方法研究了规模稻鸭生态种养、常规稻鸭生态种养和水稻单一种植稻田杂草的群落变化特点及控草效果。结果表明:规模稻鸭生态种养杂草密度显著降低,与水稻单一种植比较防效为94%;水稻分蘖到孕穗期稻田杂草主要由看麦娘(Alopecuruspratensis)、稗草(Echinochhloa crausgalli)、狗牙根(Cynodon dactylon)、水花生(Alternanthera philoxeroides)、鸭舌草(Mouochoria vaginalis)、水竹叶(Murdannia triquetra)和鳢肠(Eclipta prostrata)组成,抽穗期到成熟期主要由水花生、稗草、狗牙根和水竹叶组成。研究还表明,规模稻鸭生态种养水稻分蘖期物种丰富度、Simpon指数、Shannon-Wiener指数略高于水稻单一种植,Pielou指数低于水稻单一种植;孕穗期到成熟期物种丰富度、Simpon指数、Shannon-Wiener指数低于水稻单一种植,Pielou指数显著高于水稻单一种植。水稻全生育期规模稻鸭生态种养与常规稻鸭生态种养比较稻田杂草密度、杂草生物量和多样性指数差异不显著,但杂草生物多样性指数略有提高。说明规模稻鸭生态种养显著改变稻田杂草的群落结构和组成,可抑制杂草发生危害,达到有效控草目的。     

不同恢复方式下盐渍化弃耕地土壤生物学活性的变化

以干旱区新疆玛纳斯河流域冲积扇缘定点定位试验地为研究对象, 研究灌溉处理、人工草地处理和补植处理对盐渍化弃耕地土壤微生物量、酶活性及土壤呼吸速率的影响。结果表明, 不同恢复方式均明显增加了土壤微生物数量和土壤微生物量碳、氮及土壤酶活性。不同处理土壤微生物量碳、氮分别比原始弃耕地高17.80%、26.38%、5.33%和7.89%、12.75%、21.93%; 不同处理土壤微生物数量分别是原始弃耕地的4.72倍、6.04倍和4.56倍; 不同处理土壤蔗糖酶活性分别比原始弃耕地高3.4倍、3.2倍和7.7倍, 多酚氧化酶活性比原始弃耕地高1.7倍、1.2倍和1.5倍, 脲酶活性比原始弃耕地高11.1%、52.3%和37.1%; 灌溉处理土壤过氧化氢酶活性最高, 是原始弃耕地的1.53倍, 土壤呼吸速率变化表现为人工草地处理>灌溉处理>补植处理>原始弃耕地, 其中, 人工草地处理土壤呼吸速率比弃耕地高52.25%。相关分析表明, 微生物量碳与微生物C/N和微生物数量之间均呈显著正相关关系(P<0.05); 土壤呼吸速率与土壤脲酶、微生物数量和微生物量碳的相关性达到显著水平(P<0.05), 与土壤微生物量氮呈负相关关系, 但相关性不显著; 土壤蔗糖酶与其他3种酶以及微生物量氮呈显著正相关关系, 土壤脲酶与微生物数量呈显著正相关关系, 多酚氧化酶与过氧化氢酶相关性达到显著水平(P<0.05)。本研究表明干旱区盐渍化弃耕地采用灌溉与人工草地处理有利于土壤养分积累, 可在一定程度上改善土壤质量。     

甘蔗酒精废液对土壤理化性状及氧化还原酶的影响

在蔗地上设计不施肥(CK1)、施化肥(CK2)和4个直接喷施甘蔗酒精废液处理,研究不同用量废液施用对土壤理化性状及两种氧化还原酶活性的影响.结果表明:蔗地施用废液提高了土壤全氮、Cl-、有机质、腐殖质含量,使甘蔗苗期土壤过氧化氢酶和多酚氧化酶活性异常升高,随后迅速下降,成熟期下降到接近或小于CK2的土壤酶活性水平.甘蔗苗期土壤过氧化氢酶活性与全氮、有机质、腐殖质呈极显著正相关,与富里酸、胡敏酸、Cl-呈显著正相关(r0.05=0.811,r0.01=0.917,n=6);土壤多酚氧化酶活性与有机质、腐殖质、Cl-呈显著正相关.与不种植甘蔗的75 tCK废液处理相比,种植甘蔗的75 t废液处理甘蔗生长后期土壤全氮、有机质、Cl-含量和多酚氧化酶活性较低.说明与施用化肥或不施肥处理相比,蔗地施用废液有提高土壤肥力和有机质、腐殖质含量的作用,但也使施用初期过氧化氢酶和多酚氧化酶活性异常升高,施废液的土壤种植甘蔗对废液养分吸收和环境净化有一定作用.     

亚热带4种典型森林植被土壤固碳细菌群落结构及数量特征

为研究亚热带不同森林植被类型土壤固碳微生物特征及其影响因子,选取毛竹林(Moso banboo groves)、阔叶林(Broad-leaved forest)、杉木林(Chinese fir forest)和马尾松林(Masson pine forest)等4种森林植被为研究对象,以 cbbL为固碳细菌指示基因,利用实时荧光定量PCR (Real-time quantitative PCR)和MiSeq高通量测序为研究手段。结果表明,4种林分土壤的细菌16S rRNA基因和固碳细菌cbbL基因丰度范围分别是5.40×10~(10)～2.81×10~(11) copies·g~(-1)干土和4.55×10~8～3.53×10~9 copies·g~(-1)干土,其中毛竹林显著高于其他三种林分(P0.05);基因丰度显著关联的环境因子是阔叶林土壤的有效磷、不同土层的pH(P0.05)。杉木林土壤固碳细菌多样性显著低于其他3种林分(P0.05),其亚表层土壤高于表层(P0.05);双因子分析表明,林型、土层之间土壤固碳细菌多样性均存在显著或极显著差异。所有土壤具有相似的优势属但相对丰度不同,其中毛竹林和杉木林土壤的甲基化石油杆菌属(Methylibium)和诺卡菌属(Nocardia)占比明显高于阔叶林和马尾松林。冗余分析结果显示,不同林分土壤pH、土壤有机碳、有效磷、全氮差异是影响土壤固碳细菌群落特征形成的主要因素。综上,4种植被对土壤固碳微生物数量及群落结构多样性影响明显,从土壤理化性质、固碳细菌基因丰度、多样性以及结构特征等多维度结果证明,毛竹林对土壤肥力以及固碳细菌影响效果最好,固碳微生物对毛竹林土壤有机质积累贡献大于阔叶林,定量结论有待进一步研究。