种植模式对稻田土壤微生物数量及活度的影响

为了明确种植模式对稻田土壤微生物的影响情况，进行了少耕和翻耕时不同种植模式对稻田土壤微生物数量及活度的影响研究，结果表明：种植马铃薯、紫云英、黑麦草、油菜、小黑麦等冬季作物能够不同程度的影响土壤中微生物的数量与活度，影响程度可以表示为马铃薯〉黑麦草〉小黑麦〉紫云英〉油菜〉冬闲。在晚稻收割期，少耕土壤中的好气性细菌、厌气性细菌、真菌、放线菌数量都多于翻耕土壤。早稻收割期翻耕比少耕的微生物活度略高，而晚稻收割期翻耕比少耕的微生物略低，这与所测的几类微生物数量的基本变化规律是一致的。少耕能激活土壤中的微生物，改良土壤。     

稻草还田翻耕对水稻土微生物及酶的影响研究

稻草直接还田是一条合理利用秸秆资源齐地培肥的有效途径.为了探明翻耕条件下秸秆还田量对土壤生物学特征的影响,为制定舍理的秸秆还田量,用于早稻秸秆还田培肥土壤,减少环境的污染和保障农业的可持续性发展,进行了0%、33%、67%、100%早稻秸秆连续2年覆盖翻耕对水稻土微生物及酶活性的影响研究.结果表明:经过稻草翻耕还田后,稻田土壤的生物学性状得到了一定程度的改善.不同的稻草还田量对土壤微生物数量、微生物活度、土壤酶活性以及土壤微生物作用强度的影响存在差异,33%和67%稻草还田量较0%和100%稻草还田更能改善稻田土壤质量.     

烟草连作对旱地土壤微生物及酶活性的影响

测定了烟草不同连作年限的旱地土壤中微生物数量、活度及酶活性.结果 表明,连作8年以下的旱地土壤中的好气性细菌、厌气性细菌、放线菌及真菌的数量随连作年限增加而有上升趋势,连作8年以上的微生物数量却有下降趋势.烟草连作对旱地土壤的细菌数量影响最大,对真菌数量的影响次之,对放线菌数量的影响最小.烟草连作对旱地土壤微生物活度及土壤酶活性的影响不大.烟草长期连作将改变土壤微生物的数量及多样性,会影响连作病害的发生,不利于土壤生态系统的健康发展.     

纤维素分解混合菌群的筛选及其腐解稻草的研究Ⅰ纤维素分解混合菌群的筛选

为了得到强分解纤维素的复合微生物来配合秸秆还田，从不同生态环境的土壤中用选择性培养基进行了纤维素分解混合菌群的富集，得到了纤维素酶活性较高的混合菌群，该菌群以兼性厌气性细菌为主，能够在较短的时间内溶解滤纸。该菌群利用CMC-Na的能力比滤纸好。以稻草粉为底物时产酶的最佳尿素用量为0．1％，生长曲线表明该菌群在96h开始进入稳定生长期，筛选到了一个能够较好地腐解稻草的混合菌群。     

Microbial activity in the terrestrial subsurface

Summary Little is known about the layers under the earth's crust. Only in recent years have techniques for sampling the deeper subsurface been developed to permit investigation of the subsurface environment. Prevailing conditions in the subsurface habitat such as nutrient availability, soil composition, redox potential, permeability and a variety of other factors can influence the microflora that flourish in a given environment. Microbial diversity varies between geological formations, but in general sandy soils support growth better than soils rich in clay. Bacteria predominate in subsurface sediments, while eukaryotes constitute only 1–2% of the microorganisms. Recent investigations revealed that most uncontaminated subsurface soils support the growth of aerobic heteroorganotrophic bacteria, but obviously anaerobic microorganisms also exist in the deeper subsurface habitat. The microorganisms residing below the surface of the earth are capable of degrading both natural and xenobiotic contaminants and can thereby adapt to growth under polluted conditions.     

植物修复重金属与多环芳烃污染土壤强化措施研究进展

重金属和多环芳烃是土壤环境中的重要污染物，其复合污染土壤的修复已成为环境科学研究的热点问题。植物修复技术是目前修复土壤复合污染重要方法之一，但植物本身修复能力有限，需借助化学、微生物、基因工程等手段对其修复效果进行强化。本文对国内外近几年来植物修复重金属-多环芳烃复合污染强化措施研究成果进行综述，并重点讨论了植物根际生长促进菌及菌根在强化修复中的应用，在此基础上对未来该领域需要深入研究的科学问题进行了阐述。     

湿地甲烷排放研究进展

甲烷是一种仅次于二氧化碳的重要温室气体,对全球变暖的贡献率为25%。近年来大气中甲烷浓度显著增加,湿地甲烷释放量约占全球甲烷通量的20%,是大气甲烷的主要自然来源之一。甲烷主要通过产甲烷菌在厌氧条件下产生,在氧化条件下,甲烷通过土壤中的甲烷氧化菌氧化,并通过气泡、扩散和植物传输三种途径释放到大气。湿地甲烷通量在时间和空间两个方面有较大的变化,这与甲烷产生、氧化和传输过程有关,同时受到不同环境因素的影响,如:土壤质地、氧化还原电位、有机物、土壤酸碱度、植被条件、气候因素、农业管理措施等。文章还对湿地甲烷排放的观测方法和排放模型进行了简单介绍,并对今后的研究提出了几点建议。     

无溶剂微波辅助-液相微萃取测定土壤中的滴滴涕

建立了一种快速、有效、环境友好的样品前处理方法，即无溶剂微波辅助-液相微萃取技术，并结合高效液相色谱法对土壤中的滴滴涕残留进行了测定分析，同时对影响萃取效率的相关因素，如萃取溶剂的种类、微波辐射功率、萃取时间和pH等因素进行了优化。最终确定最佳优化条件为：萃取溶剂为正庚烷，微波辐射功率为120w，萃取时间为1rain，pH为5。在最优条件下，滴滴涕的检出限（S／N=3）为0．18μg／kg，定量限（S／N=10）为0．59μg／kg，实际土壤加标回收率87．34％～96．41％之间，相对标准偏差RSDs在5．75％～6．72％之间。理论分析和实验结果表明，该方法具有操作简便，节省溶剂，快速，高效，选择性好等特点。     

燕山中元古界大红峪组微生物席碎片的发现及初步研究

元古代碳酸盐岩沉积孕育了大量与微生物活动有关的沉积构造，但是对于相同时期的碎屑岩沉积环境中微生物引起的沉积构造的研究却很少。在元古代碎屑岩沉积环境中发现的最常晃的与微生物活动有关的沉积构造是皱饰构造和变余波痕，前人研究结果已经证明它们为微生物引起的沉积构造。在华北地台中元古界长城系大红峪组砂岩层面上发育一些与变余波痕和皱饰构造共生的一种特殊的沉积现象，即纺锤状砂质碎片。通过研究证实这些砂质碎片是微生物与物理营力相互作用形成的，也就是微生物席碎片。其发现有益于以后对类似沉积构造的研究；也有助于认识和了解中元古代生物群演化、古生命环境。     

Formation of ethanol by bacteria. A pledge for the use of extreme thermophilic anaerobic bacteria in industrial ethanol fermentation processes

Summary Many anaerobic, facultatively anaerobic and even some strictly aerobic microorganisms form various amounts of ethanol from glucose. Only few mesophilic and extreme thermophilic bacteria ferment glucose stoichiometrically to 2 ethanol and 2 carbondioxid. Biotechnological processes at elevated temperatures seem advantageous in many respects. Hence, thermophiles and extreme thermophiles can potentially substitute for yeast in ethanol production on an industrial scale. Advantages and disadvantages of thermophilic mixed cultures and of potentially useful organisms are discussed.Acknowledgment. This work was partly supported by Energy and Research Development Administration contract number EY-76-509-0888-M003 and by the Deutsche Forschungsgemeinschaft.     

Plant growth stimulation by inoculation with symbiotic and associative rhizosphere microorganisms

SelectedRhizobium bacteria, arbuscular mycorrhiza-forming (AM) fungi and associative bacteria have been shown to stimulate the growth of legumes, gramineae and cruciferae in field experiments on different soil types in temperate regions. A combination of microorganisms with different metabolic capacities (N₂-fixation, P-mobilization; production of phytohormones and antibiotics) can partly surpass the effect of single inoculations, or can produce a positive effect where single inoculations are ineffective. Growth stimulation by inoculation requires microorganisms with phytoeffective metabolic characteristics and the ability to survive in the rhizosphere during the growth period. Another prerequisite is an adequate supply of plant assimilates for the production of microbial phytoeffective metabolites. Type of inoculum, method of inoculation and agricultural measures can influence the effect of the inoculation. Research is necessary to extend our knowledge both of basic principles, and about using microorganisms in practice.     

The Swedish final repository and the possible risk of interactions by microbial activities

Summary The final Swedish repository for low- and intermediate-level nuclear waste is described, and some of the possible problems caused by microbial activity during storage are discussed. Microbial degradation of bitumen constitutes one of the greatest risks in the silo part of a repository. The production of carbon dioxide due to both aerobic and anaerobic processes might lead to a decrease in the pH of the water, inducing corrosion of the metal construction and storage containers, with large amounts of hydrogen gas being produced. A risk assessment for the repository must thus take into account the various activities of microbes.     

The role of conjugative transposons in spreading antibiotic resistance between bacteria that inhabit the gastrointestinal tract

There is huge potential for genetic exchange to occur within the dense, diverse anaerobic microbial population inhabiting the gastrointestinal tract (GIT) of humans and animals. However, the incidence of conjugative transposons (CTns) and the antibiotic resistance genes they carry has not been well studied among this population. Since any incoming bacteria, including pathogens, can access this reservoir of genes, this oversight would appear to be an important one. Recent evidence has shown that anaerobic bacteria native to the rumen or hindgut harbour both novel antibiotic resistance genes and novel conjugative transposons. These CTns, and previously characterized CTns, can be transferred to a wide range of commensal bacteria under laboratory and in vivo conditions. The main evidence that gene transfer occurs widely in vivo between GIT bacteria, and between GIT bacteria and pathogenic bacteria, is that identical resistance genes are present in diverse bacterial species from different hosts.