刈割对草原化荒漠区驼绒藜(Krascheninnikovia ceratoides)根际土壤特性的影响

在休眠期对草原化荒漠中自然生长的驼绒藜(Krascheninnikovia ceratoides)进行不同频度的刈割处理(连年刈割、隔年刈割、对照),通过测定根际土壤理化性质、土壤微生物数量及土壤酶活性等指标,分析和讨论了不同频度的刈割处理对驼绒藜根际土壤特性的影响。结果表明:(1)连年刈割和隔年刈割都显著提高了根际土壤含水量,隔年刈割使根际土壤全碳含量显著上升、有机质含量显著下降,但刈割对根际土壤pH值和全氮含量的影响不明显;(2)刈割对根际土壤微生物总量的影响不明显,但显著影响细菌、真菌和放线菌的组成,连年刈割使真菌数量显著增加,隔年刈割使放线菌数量显著增加,驼绒藜根际土壤中放线菌所占比例最大,其数量表征了土壤的贫瘠程度;(3)刈割对根际土壤过氧化氢酶和中性磷酸酶活性有显著影响,两种刈割处理会显著提高土壤过氧化氢酶活性、降低土壤中性磷酸酶活性,而对土壤多酚氧化酶、脲酶、转化酶和碱性磷酸酶活性的影响不显著。总之,隔年刈割对植物根际土壤养分供给及土壤分解者的活性更加有利,而且土壤理化因子对土壤微生物数量和土壤酶活性的影响不显著。刈割对驼绒藜根际土壤特性影响的规律性不强,可能是由于半灌木刈割利用的时间较短,根际土壤各个测量指标之间尚未形成显著的相关性。     

Interactions between larvae of the hoverfly <Emphasis Type="Italic">Eristalinus sepulchralis</Emphasis> and microorganisms in the hydrothermal springs of the Uzon caldera,Kamchatka

The physicochemical and microbial characteristics of some medium-temperature hydrotherms of Kamchatka Peninsula (Uzon caldera), habitats of the hoverfly Eristalinus sepulchralis larvae, were studied. In these hydrothermal vents, the larvae were found to use various prokaryotic and eukaryotic microorganisms as a nutrient substrate. The rates of chemo-and photosynthetic activity of the suspended microbial communities inhabiting the hydrotherms and supporting the existence of larvae were measured. By light and electron microscopy, exo-and endosymbiotic prokaryotic microorganisms were revealed in the digestive and respiratory systems of larvae.     

Diversity of halophilic microorganisms: Environments,phylogeny, physiology,and applications

The phylogenetic diversity of microorganisms living at high salt concentrations is surprising. Halophiles are found in each of the three domains: Archaea, Bacteria, and Eucarya. The metabolic diversity of halophiles is great as well: they include oxygenic and anoxygenic phototrophs, aerobic heterotrophs, fermenters, denitrifiers, sulfate reducers, and methanogens. The diversity of metabolic types encountered decreases with salinity. The upper salinity limit at which each dissimilatory process takes place is correlated with the amount of energy generated and the energetic cost of osmotic adaptation. Our understanding of the biodiversity in salt-saturated environments has increased greatly in recent years. Using a combination of culture techniques, molecular biological methods, and chemotaxonomic studies, we have obtained information on the nature of the halophilic Archaea as well as the halophilic Bacteria that inhabit saltern crystallizer ponds. Several halophilic microorganisms are being exploited in biotechnology. In some cases, such as the production of ectoine, the product is directly related to the halophilic behavior of the producing microorganism. In other cases, such as the extraction of β-carotene from Dunaliella or the potential use of Haloferax species for the production of poly-β-hydroxyalkanoate or extracellular polysaccharides, similar products can be obtained from non-halophiles, but halophilic microorganisms may present advantages over the use of non-halophilic counterparts. Journal of Industrial Microbiology & Biotechnology (2002) 28, 56–63 DOI: 10.1038/sj/jim/7000176 Received 20 May 2001/ Accepted in revised form 20 June 2001     

Characterisation of Rubus niveus: a prerequisite to its biological control in oceanic islands

This study is intended to inform the search for a biocontrol solution to stem the spread of Rubus niveus, a morphologically-diverse and invasive Rubus species which has become an aggressive invader in areas of the world outside its native range. The fragile biodiversity of islands can be especially threatened by this plant – exemplars of this are the Galápagos archipelago and Hawaii. This report focuses on the morphological and molecular work carried out to establish the homogeneity or intra-specific variation of R. niveus populations within the Galápagos Islands, as well as their kinship with plants of the same name found in Asia. The premise of this study is that genetic closeness between these populations offers increased probability that pathogens of R. niveus in its native range will also provide effective control in the target environment. Increased knowledge of the genetic make-up of R. niveus in both its native and naturalised locations will also help to assess the feasibility of using organisms which have been found to be effective against other Rubus species, but not hitherto considered for R. niveus itself.     

半导体矿物介导非光合微生物利用光电子新途径

自然界中微生物按其能量代谢途径主要分为两种:光能营养微生物和化能营养微生物.化能营养微生物作为非光能营养微生物长期被排除在以日光为能量来源的能量利用途径之外.本文介绍了一种新的微生物能量利用途径,即非光能营养微生物通过半导体矿物光催化作用来利用太阳能进行生长.实验室模拟体系中,金属氧化物、金属硫化物等天然半导体矿物在模拟日光激发下产生的光电子促进了化能自养与异养微生物的生长.研究结果表明微生物的生长与光子能量和光子数量密切相关,同时不同波长光辐照下的微生物生长情况与矿物的光吸收谱相吻合.这一能量利用途径的光能-生物能转化效率为0.13‰-1.90‰.在含有天然半导体矿物与天然微生物的红壤体系中,进一步发现半导体矿物光催化能够明显改变环境微生物的种群结构.已有的研究揭示了一种新发现并极有可能长期在地球上存在的微生物能量利用途径,即通过自然界中半导体矿物日光催化作用产生的光电子能够促进非光能营养微生物的生长代谢活动.     

Belowground community responses to fire: meta‐analysis reveals contrasting responses of soil microorganisms and mesofauna

Global fire regimes are shifting due to climate and land use changes. Understanding the responses of belowground communities to fire is key to predicting changes in the ecosystem processes they regulate. We conducted a comprehensive meta‐analysis of 1634 observations from 131 empirical studies to investigate the effect of fire on soil microorganisms and mesofauna. Fire had a strong negative effect on soil biota biomass, abundance, richness, evenness, and diversity. Fire reduced microorganism biomass and abundance by up to 96%. Bacteria were more resistant to fire than fungi. Fire reduced nematode abundance by 88% but had no significant effect on soil arthropods. Fire reduced richness, evenness and diversity of soil microorganisms and mesofauna by up to 99%. We found little evidence of temporal trends towards recovery within 10 years post‐disturbance suggesting little resilience of the soil community to fire. Interactions between biome, fire type, and depth explained few of these negative trends. Future research at the intersection of fire ecology and soil biology should aim to integrate soil community structure with the ecosystem processes they mediate under changing global fire regimes.     

Functional diversity of soil microorganisms in Casuarina equisetifolia woodlands of different stand ages in Hainan Island

为研究不同林龄木麻黄(Casuarina equisetifolia)林地土壤微生物功能多样性的动态变化, 通过Biolog系统对海口市桂林洋开发区滨海不同林龄(幼龄林(林龄5-8年)、中龄林(林龄15-20年)和成熟林(林龄30年及以上))的木麻黄林地土壤微生物的功能多样性进行了分析。结果表明: (1)对照裸地和成熟林林地土壤微生物对所使用的Biolog-ECO微孔板中的31种碳源的利用率和对这31种碳源的各分类碳源的利用率高于中龄林与幼龄林林地; (2) Shannon-Wiener指数(H′), McIntosh、Simpson多样性指数随着林龄增大而增大, 不同林龄林地间的H′差异显著, 幼龄林和中龄林的McIntosh、Simpson多样性指数无显著差异; (3)主成分分析结果表明, 在主成分分离中起分异作用的主要碳源为单糖和氨基酸。林地土壤微生物群落多样性随着林龄增加而增高, 这可能是林分凋落物、植物根系分泌的次生代谢物、土壤养分、林地土壤特异性微生物等共同作用的结果。     

生物转化生产D-塔格糖的食品级菌种选育及L-阿拉伯糖异构酶的克隆表达

L-阿拉伯糖异构酶(L-arabinose isomerase,L-AI)是一种可以催化D-半乳糖为D-塔格糖的胞内异构化酶。随着塔格糖在食品工业中越来越广泛的应用,能够将半乳糖转化为塔格糖的食品级微生物以及食品级来源的L-AI受到更大的关注。文中从各种酸奶制品、泡菜及其他一些食品中采集不同的样品,筛选出1株具有L-AI酶活的食品级菌株,经过生理生化鉴定以及16S rDNA序列测定,确定该菌株为戊糖片球菌,命名为Pediococcus pentosaceus PC-5。以该菌基因组为模板,克隆L-AI基因,并在大肠杆菌BL21成功地异源表达。表达产物经粗提取后,在40℃下加入Mn2+,使D-半乳糖转化为D-塔格糖的转化率为33%。     

海洋微生物抗菌脂肽及新生物农药研发

近年来,微生物脂肽作为生物农药的研究与应用,在国内外得到了广泛重视,成为今后生物农药发展的一个重要方向。从不同生境分离获得多批海洋微生物,通过筛选抗植物病原真菌活性强的菌株,发酵、分离、纯化及鉴定其代谢产物,从3种芽胞杆菌中发现了6个新的抗菌脂肽,属于iturins和fengycin类化合物。芽胞杆菌的芽胞及脂肽可研发防治植物真菌病害新生物农药。     

Variations of soil structure and microbial population in a compost amended soil

Changes in soil structure and in microbial population were recorded in a long term field experiment over the growing season of maize (June–November). Determinations were made on samples from plots which had received, for two years, the following treatments: mineral fertilizers, farmyard manure and three rates of compost. Seasonal variations were observed for the stability of soil aggregates, total porosity, pore size distribution, mycorrhizal infection and aerobic cellulolytic microorganisms. The stability of the soil aggregates changed in a similar way to that found for both mycorrhizal infection and the number of aerobic cellulolytic microorganisms. Physical characteristics were not affected in any instance by the organic dressings and microbiological populations were generally influenced only by the higher doses of compost.