高浓度酒精废水厌氧处理工程系统中古菌多样性及其代谢特征

颗粒污泥形成快、抗冲击能力强、悬浮性好是新型高浓度有机废水厌氧处理系统的重要特征。为了研究颗粒污泥中古菌组成多样性及其功能特征, 采集活性污泥样品, 提取总基因组DNA, 应用PCR-DGGE和16S rDNA克隆测序技术对系统内古菌群落进行研究。结果表明: 古菌克隆文库中克隆子的近缘种归属于Methanosaeta、Methanosarcina、Methanobacterium和Methanomethylovorans 4个类群, 所占文库容量比例依次为58.2%、23.6%、12.7%和3.6%, 1个克隆子未能找到相似菌株, 占1.8%。系统发育分析找到了未知克隆子C10、C11、C13和C19的相似菌株FJ618821、AB479397、AJ244290和AB447878, 并明确相应的分类地位。古菌类群以乙酸利用型Methanosaeta、Methanosarcina为主, 说明甲烷形成过程以乙酸途径为主。中间代谢产物VFAs组成与不同产甲烷菌代谢功能分析的结果证明了古菌群落组成多样性与其代谢功能的对应关系。     

Creating a community resource for protein science

Helen Berman is the recipient of the Protein Society 2012 Carl Branden Award In addition to being one of the early pioneers in protein crystallography, Carl Brändén made significant contributions to science education with his elegant and beautifully illustrated book Introduction to Protein Structure (Brändén and Tooze, New York: Garland, 1991). It is truly an honor to receive this award in their names. This award and the 40th anniversary of the Protein Data Bank (PDB; Berman et al., Structure 2012;20:391–396) have given me an opportunity to reflect on the various components that have contributed to building a resource for protein science and to try to quantify the impact of having PDB data openly available.     

Interactions between extraradical ectomycorrhizal mycelia, microbes associated with the mycelia and growth rate of Norway spruce (Picea abies) clones

Despite their ecological relevance, field studies of the extraradical mycelia of ectomycorrhizal (ECM) fungi are rare. Here we examined in situ interactions between ECM mycelia and host vigour. Ectomycorrhizal mycelia were harvested with in-growth mesh bags buried under Norway spruce (Picea abies) clones planted in 1994 in a randomized block design. Mycelial biomass was determined and fungal species were identified by denaturing gradient gel electrophoresis (DGGE) and sequencing of the internal transcribed spacer 1 (ITS1) region. Microbial community structure in the mycelium was investigated by phospholipid fatty acid (PLFA) profiling. Compared to slow-growing spruce clones, fast-growing clones tended to support denser mycelia where the relative proportions of Atheliaceae fungi and PLFAs indicative of Gram-positive bacteria were higher. Ascomycetes and PLFAs representative of Gram-negative bacteria were more common with slow-growing clones. In general, the ECM mycelial community was similar to the ECM root-tip community. Growth rate of the hosts, the ECM mycelial community and the microbes associated with the mycelium were related, suggesting multitrophic interactions between trees, fungi and bacteria.     

Effect of Soybean Monoculture on the Bacterial Communities Associated with Cysts of Heterodera glycines

The soybean cyst nematode (SCN), Heterodera glycines, can cause significant reductions in soybean yield and quality in many parts of the world. Natural biological control may play an important role in regulating SCN population. In this study the bacterial communities associated with SCN cysts obtained from fields under different lengths of soybean monoculture were explored. Soil samples were collected in 2010 and 2011 from six fields that had been used for soybean monoculture for 2 to 41 yr. SCN population densities were determined and bacterial communities from SCN cysts were investigated by Biolog and PCR-DGGE methods. SCN population densities initially increased in the first 5 yr of soybean monoculture but then declined steeply as years of soybean monoculture increased. Catabolic diversity of bacterial communities associated with cysts tended to decline as number of years of monoculture increased. Some specific PCR-DGGE bands, mainly representing Streptomyces and Rhizobium, were obtained from the cysts collected from the long-term monoculture fields. Principal component analysis of Biolog and PCR-DGGE data revealed that bacterial communities associated with cysts could be divided into two groups: those from cysts obtained from shorter (< 8 yr) vs. longer (> 8 yr) monoculture. This research demonstrates that the composition of the bacterial communities obtained from SCN cysts changes with length of soybean monoculture; the suppressive impact of these bacterial communities to SCN is yet to be determined.     

金沙江干旱河谷退化草地群落对氮磷施肥的反应

在云南省境内的金沙江干旱河谷区, 选择退化严重的草地群落研究氮磷施肥对群落动态的影响。经过一个生长季的施肥处理, 结果表明, 除大量施磷肥处理(20 g·a^-1·m^-2)时, 可能因施磷过多群落生物量和密度没有出现增加外。其余的施氮和施磷处理均导致群落地上生物量和密度增加, 而且施氮处理引起群落地上生物量和密度增加的程度都高于施磷处理。说明在干旱河谷退化严重的草地生态系统, 氮是限制系统恢复的主要因素。施肥后禾本科草本植物密度大量增加, 而乔灌木密度增加不明显, 群落在短期内变成以禾本科草本植物为主的状态。施氮和施磷没有引起群落种数量和植物多样性指数的明显变化。试验结束时土壤的铵态氮、硝态氮和有效磷浓度没因施肥而增加, 但施肥处理的植物体氮和磷浓度增加。     

Effects of Prescribed Fire on Shinnery Oak ( Quercus havardii) Plant Communities in Western Oklahoma

Changes in structural and compositional attributes of shinnery oak (Quercus havardii Rydb.) plant communities have occurred in the twentieth century. These changes may in part relate to altered fire regimes. Our objective was to document effects of prescribed fire in fall (October), winter (February), and spring (April) on plant composition. Three study sites were located in western Oklahoma; each contained 12, 60 × 30‐m plots that were designated, within site, to be seasonally burned, annually burned, or left unburned. Growing season canopy cover for herbaceous and woody species was estimated in 1997–1998 (post‐treatment). At one year post‐fire, burning in any season reduced shrub cover, and spring burns reduced cover most. Winter and annual fires increased cover of rhizomatous tallgrasses, whereas burning in any season decreased little bluestem cover. Perennial forbs increased with fall and winter fire. Shrub stem density increased with fire in any season. Communities returned rapidly to pre‐burn composition with increasing time since fire. Fire effects on herbaceous vegetation appear to be manifested through increases in bare ground and reduction of overstory shrub dominance. Prescribed fire can be used as a tool in restoration efforts to increase or maintain within and between community plant diversity. Our data suggest that some plant species may require or benefit from fire in specific seasons. Additional research is needed to determine the long‐term effects of repeated fire over time.     

广西天然林中藤本植物区系组成及系统发育多样性

藤本植物是热带和亚热带森林的重要组分,在过去几十年中藤本植物多样性在热带森林增加,有可能导致森林的多样性减少,碳储量等生态系统服务功能降低,引起广泛关注。以《广西植被志要》中共355个样地数据(喀斯特森林、海拔1000 m以下的非喀斯特森林和海拔1000 m以上的非喀斯特森林)为基础,结合气候数据,分析天然林中藤本植物区系组成、不同生境藤本植物物种多样性与系统发育多样性关系、藤本植物物种多样性与年平均温度关系,以及系统发育结构特点。结果表明:(1)广西天然林藤本植物中,热带分布的含藤属占比最大(75.4%),温带分布含藤属占比较低(12.3%),世界广布含藤属和亚洲分布含藤属占比最小,海拔1000 m以下的喀斯特和非喀斯特森林都有一些专有的含藤科属;(2) 3个生境藤本的Gleason物种多样性和系统发育多样性与年均温都不相关,它们的物种多样性差异不显著,但是系统发育多样性有显著差异,海拔1000 m以下的非喀斯特森林中系统发育多样性最高,喀斯特森林系统发育多样性最低;(3)非喀斯特森林藤本植物系统发育结构趋向于离散,暗指竞争排斥作用是藤本植物组合在该生境群落主要构建机制,喀斯特森林藤本植物系统发育结构趋向于聚集,暗指藤本植物组合由生境过滤作用为主形成。这些研究发现对于热带亚热带森林藤本植物的多样性组成及其共存机制提供了新认识。     

不同类型人工湿地微生物群落的研究进展

微生物是人工湿地不可缺少的成员,对湿地生态系统中物质转化、能量流动起着重要作用.本文从人工湿地微生物群落的研究方法、微生物群落结构与组成、微生物群落调节作用与环境因素的关系等方面,综述了人工湿地微生物的研究进展.各种新颖的分子生物学方法已经成为研究人工湿地的微生物多样性的有力工具,其中最常见的是变性梯度凝胶电泳(DGGE)和寡核苷酸荧光探针原位杂交(FISH);人工湿地微生物群落的调节作用主要取决于湿地的水文条件、废水的特点(包括组成成分,污染物的特点和利用性)、湿地的过滤材料或土壤类型、植物和各种环境因素;不同人工湿地类型的微生物群落组成,从多到少依次是变形菌、噬纤维菌.黄杆菌菌群、放线菌和厚壁菌.如何进一步加深对氮循环相关微生物多样性的研究,提高废水中氮的去除效率依然是未来人工湿地技术需要解决的重要问题之一.     

Endosymbiont metacommunities,mtDNA diversity and the evolution of the Bemisia tabaci (Hemiptera: Aleyrodidae) species complex

Bemisia tabaci, an invasive pest that causes crop damage worldwide, is a highly differentiated species complex, divided into biotypes that have mainly been defined based on mitochondrial DNA sequences. Although endosymbionts can potentially induce population differentiation, specialization and indirect selection on mtDNA, studies have largely ignored these influential passengers in B. tabaci, despite as many as seven bacterial endosymbionts have been identified. Here, we investigate the composition of the whole bacterial community in worldwide populations of B. tabaci, together with host genetic differentiation, focusing on the invasive B and Q biotypes. Among 653 individuals studied, more than 95% of them harbour at least one secondary endosymbiont, and multiple infections are very common. In addition, sequence analyses reveal a very high diversity of facultative endosymbionts in B. tabaci, with some bacterial genus being represented by more than one strain. In the B and Q biotypes, nine different strains of bacteria have been identified. The mtDNA‐based phylogeny of B. tabaci also reveals a very high nucleotide diversity that partitions the two ITS clades (B and Q) into six CO1 genetic groups. Each genetic group is in linkage disequilibrium with a specific combination of endosymbionts. All together, our results demonstrate the rapid dynamics of the bacterial endosymbiont–host associations at a small evolutionary scale, questioning the role of endosymbiotic communities in the evolution of the Bemisia tabaci species complex and strengthening the need to develop a metacommunity theory of inherited endosymbionts.