柑桔溃疡病菌滚环扩增检测体系的建立

根据柑桔溃疡病菌(Xanthomonas axonopodis pv.citri,Xac)独有的蛋白基因序列和锁式探针公共连接序列分别设计特异性的锁式探针及其扩增引物,优化系列反应条件,建立了特异性的柑桔溃疡病菌滚环扩增体系.初步检测结果表明该体系能够特异性地检出Xac的菌体细胞及其DNA,而检测不出供试的其它植物病原细菌和柑桔叶面常见的多种附生细菌;对Xac靶片段克隆质粒DNA的检测灵敏度为10 2 copy/μL,对Xac菌悬液的检测灵敏度为20 cfu/μL,比常规PCR的检测灵敏度稍高.用滚环扩增技术和常规PCR技术对田间采集的实际样品进行了检测,两种方法的检测结果没有显著差异(P＞0.01).由于锁式探针的公共连接序列对扩增的条件要求一致,本体系的建立可以为植物病原微生物多靶标检测和病害检疫检验提供新的技术支撑.     

应用杀菌剂对果园土壤AM菌的影响研究

试验研究了几种农用杀菌剂和除草剂对土壤丛枝菌根真菌孢子形成和柑桔根系菌根形成的影响。结果表明:大多数杀菌剂的施用显著地抑制了土壤有益微生物的生长和活动,克菌丹对其它土壤微生物抑制的同时并不影响丛枝菌根真菌的生长,田间应用菌根真菌接种时,结合应用克菌丹处理提高了接种的有效性。     

中国柑橘园柑桔潜叶蛾雄虫对性诱剂趋向的昼夜节律

柑桔潜叶蛾Phyllocnistis citrella Stainton是柑桔重要害虫之一.本文研究了从美国引进的性诱剂对柑桔潜叶蛾雄虫的引诱活性和引诱的日节律,结果表明该性诱剂对广州、深圳和江西新余地区的柑桔潜叶蛾雄虫有显著的引诱活性.性诱剂对柑桔潜叶蛾雄虫的诱捕数量日节律明显,4:00～6:00诱集到的雄虫数量最多,3:00～4:00和6:00～11:00诱集到少量雄虫,其它时间没有诱集到雄虫.     

14个南丰柑桔品种及品系间的ISSR遗传多样性分析

柑桔是江西省南丰县生物资源中十分有特色的种质资源.本研究利用ISSR分子标记对南丰柑桔品种的遗传多样性进行研究.从100个ISSR引物中筛选出17个多态引物,对14份柑桔样品进行ISSR-PCR分析.结果显示,共扩增出162条DNA条带,其中多态性条带为134条,占82.71%,其片段大小在200～2 000bp之间.UPGMA聚类分析结果表明,以遗传相似系数为0.67为分界线,可以将14份供试柑桔样品分成三类:第一类包含以ss-28为代表的7个柑桔品种;第二类包含以杨小2,6为代表的3个柑桔品种;第三类包括以早系97-1为代表的4个柑桔品种.本研究结果对于南丰蜜桔的辅助育种或品种(株系)苗木鉴别具有重要的参考价值.     

柑桔"以螨治螨"生物防治技术研究

柑桔病虫害发生种类多,为害重,生产上喷药次数多,果品存在农药残留高,为了使我市柑桔达到无公害生产水平,减少化学农药使用量,提高柑桔品质,笔者通过释放捕食螨Amblyseius spp.建立捕食螨种群,同时结合使用生物农药和电子灭虫灯,以及白花草Ageratum conyzoides L.等栽培措施,达到了长期持续控制柑桔病虫发生的目的,而且减少我县柑桔生产的农药残留问题,降低生产成本,减少环境污染.     

大豆柑桔间作系统中磷的分配和迁移规律研究

用微区试验和³²P同位素示踪技术,比较研究了大豆、柑桔间作和单作条件下,P在大豆和柑桔体中的分配、转移及其在土壤中的迁移规律.结果表明,间作大豆的吸P量和各部位累积P量显著地低于单作大豆;³²P肥料浅施,间作大豆吸收的³²P量显著低于单作大豆;³²P肥料深施,间作大豆吸收的³²P量显著高于单作大豆,但间作不影响P和³²P在各部位的转移和分配.间作柑桔吸收的³²P量显著低于单作柑桔.柑桔新吸收的³²P可快速向地上部分输送,并优先供应生长活跃部位.间作不影响³²P在柑桔各部位的转移和分配,但是P肥深施使柑桔吸收的³²P向地上部分和生长活跃部位的转移速率减慢.间作使土壤中P的生物移动性增强,可促进土壤深层P向土壤浅层迁移.试验结果表明,大豆柑桔间作磷肥的施用深度以保持在20cm以内为佳.     

中国亚热带地区柑桔的气候适宜性

应用生态适宜度理论和模糊数学方法,建立柑桔气候适宜度模型,对中国亚热带地区柑桔生产的气候适宜性及其时空差异进行了计算、评价,并分析了中国亚热带地区柑桔各生育期气候适宜性以及中国亚热带地区各县区的平均气候适宜度.结果表明:柑桔花芽分化期、发芽期、果实成熟期的适宜性较低、风险较高,其他各生育期的适宜性较高、风险较低,影响中国亚热带地区柑桔生产的关键问题是冷害和伏旱.柑桔温度适宜性的地域分异呈纬度地带性规律;降水适宜度最适宜型分布在亚热带中部"射阳-那坡"一线区域,其东南为适宜型区,西北为次适宜型区,高山区为不适宜型区;日照适宜度与实际日照时数的区域变化规律基本一致,大致呈高纬度区高于低纬度区、高海拔区高于低海拔区;受温度因子的限制,气候适宜度与温度适宜度的分布情况大体一致,南部大于北部,基本也呈纬度地带性规律.从中国亚热带地区柑桔气候适宜度的年际变化分析可知,整个亚热带地区柑桔气候适宜度呈下降趋势,且存在区域差异,说明气候变化引起了中国亚热带柑桔适宜区和关键生育期的变动.     

大豆-柑桔间作系统中作物对磷的吸收利用特性

微区试验和^32P同位素示踪技术研究大豆-柑桔间作系统中大豆和柑桔对不同土层中磷的吸收特征表明,大豆-柑桔间作大豆与柑桔对浅层磷具有强烈竞争作用,大豆和柑桔对浅层磷的利用率分别降低41．5％和14．7％,浅层磷肥对大豆和柑桔的供应量分别降低346．8mg／区和148．1mg／区。柑桔对土壤深层磷的吸收能力比大豆强,单作大豆对浅层磷的利用率比单作柑桔高104．8％,而对35cm和55cm土层磷的利用率分别比单作柑桔低25．6％和878．3％。大豆基本不能利用55cm及其以下的磷,利用率小于0．1％。大豆-柑桔间作可以提高大豆对深层磷肥的利用率,间作大豆对35cm和55cm土层磷肥的利用率比单作大豆分别高32．3％和175．0％。     

龙眼荔枝卷叶蛾类寄主植物种类的初步研究

对广西龙眼荔枝卷叶蛾类寄主植物种类的初步考查结果表明,目前所采到的卷叶蛾种类中,它们的寄主范围不尽相同。柑桔褐带卷蛾Adoxophyes cyrtosema达15科31种;柑桔长卷蛾Homona coffearia和棉褐带卷蛾A.orana的寄主分别有14科21种和13科20种;后黄卷蛾Cacoecia asiatica和柑桔黄卷蛾Archips seminubibis的寄主有10科14种和8科13种;三角新小卷蛾Olethreutes leucaspis、圆角卷蛾Ebodocellerigera和斜斑小卷蛾Andrioplecta oxystaura,目前仅发现危害龙眼及荔枝。新发现柑桔长卷蛾可危害翠蜜枣、指天椒和皱果苋,柑桔黄卷蛾危害粪箕笃、苦丁茶、指天椒,柑桔褐带卷蛾可危害黑面神(Breyniafruticosa)。     

桔园施用有机肥对主要害虫发生的影响

为了通过合理施肥控制柑桔害虫的发生、从而减少喷施防虫农药的次数,本研究在桔园比较了单施有机肥、单施化肥的柑桔树上柑桔木虱Diaphorina citri Kuwayama、柑桔全爪螨Panonychus citri McGregor、柑桔潜叶蛾Phyllocnistis citrella Stainton等主要害虫的发生数量。结果表明,单施有机肥柑桔木虱、柑桔全爪螨发生数量显著低于常规施用化肥的施肥方法,柑桔潜叶蛾的为害没有显著变化,柑桔长势、果实可溶性固形物也没有显著改变。说明施用有机肥可以减少柑桔木虱和柑桔全爪螨的发生,而对柑桔树的长势、果品质量没有不利影响。     

Oxidation of sulfur-containing substrates by aboriginal and experimentally designed microbial communities

Aboriginal and experimental (constructed of pure microbial cultures) communities of acidophilic chemolithotrophs have been studied. The oxidation of elemental sulfur, sodium thiosulfate, and potassium tetrathionate as sole sources of energy has been monitored. The oxidation rate of the experimental community is higher as compared to the aboriginal community isolated from a flotation concentrate of pyrrhotine-containing pyrite-arsenopyrite gold-arsenic sulfide ore. The degree of oxidation of the mentioned S substrates amounts to 17.91, 68.30, and 93.94% for the experimental microbial community and to 10.71, 56.03, and 79.50% for the aboriginal community, respectively. The degree of oxidation of sulfur sulfide forms in the ore flotation concentrate is 59.15% by the aboriginal microbial community and 49.40% by the experimental microbial community. Despite a higher rate of oxidation of S substrates as a sole source of energy by the experimental microbial community, the aboriginal community oxidizes S substrates at a higher rate in the flotation concentrate of pyrrhotine-containing pyrite-arsenopyrite gold-arsenic sulfide ore, from which it was isolated. Bacterial-chemical oxidation of the flotation concentrate by the aboriginal microbial community allows for the extraction of an additional 32.3% of gold from sulfide minerals, which is by 5.7% larger compared to the yield obtained by the experimental microbial community.     

Microbial community and biomass characteristics associated severe membrane fouling during start-up of a hybrid anoxic-oxic membrane bioreactor

In MBR, severe membrane fouling is often observed in the initial phase in which biomass is yet fully acclimated and stabilized in terms of microbial community structure and biomass characteristics. The focus of this study was to investigate the microbial community development and its influence on biomass characteristics and membrane fouling during start-up of a hybrid anoxic-oxic MBR. PCR-DGGE analysis indicated that the microbial community shifted in start-up period when a severe membrane fouling was observed. Small particle size, high fractal dimension (DF) and high EPS production, which were closely associated with microbial community, were found to be the major contributors to the severe fouling. Microbial community development was most likely the ultimate factor responsible for the severe membrane fouling.     

Plant Communities, Soil Microorganisms, and Soil Carbon Cycling: Does Altering the World Belowground Matter to Ecosystem Functioning?

Soil microorganisms mediate many critical ecosystem processes. Little is known, however, about the factors that determine soil microbial community composition, and whether microbial community composition influences process rates. Here, we investigated whether aboveground plant diversity affects soil microbial community composition, and whether differences in microbial communities in turn affect ecosystem process rates. Using an experimental system at La Selva Biological Station, Costa Rica, we found that plant diversity (plots contained 1, 3, 5, or > 25 plant species) had a significant effect on microbial community composition (as determined by phospholipid fatty acid analysis). The different microbial communities had significantly different respiration responses to 24 labile carbon compounds. We then tested whether these differences in microbial composition and catabolic capabilities were indicative of the ability of distinct microbial communities to decompose different types of litter in a fully factorial laboratory litter transplant experiment. Both microbial biomass and microbial community composition appeared to play a role in litter decomposition rates. Our work suggests, however, that the more important mechanism through which changes in plant diversity affect soil microbial communities and their carbon cycling activities may be through alterations in their abundance rather than their community composition.     

rRNA-targeted寡核苷酸探针识别活性污泥微生物群落结构与功能研究进展

活性污泥中微生物群落内部关系非常复杂 ,及时对活性污泥中优势菌群和群落内部关系进行监测是污水处理中采取正确措施的关键。历史研究表明传统培养方法经常导致活性污泥优势菌群检测的失败 ,而r RNA- targeted寡核苷酸探针作为一种快速原位监测活性污泥微生物群落结构和功能的新工具被引入 ,使我们对参与污水净化的微生物群落结构和优势菌群能有较全面的了解。就该方法在识别除磷污泥、脱氮污泥、污泥泡沫和膨胀污泥中微生物群落结构和功能的典型应用进行综述 ,分析了该方法存在的优点和缺点 ,并对目前已建立且应用于活性污泥微生物检测的 r RNA- targeted寡核苷酸探针进行了详细总结     

Anthropogenic activities change the relationship between microbial community taxonomic composition and functional attributes

Functional redundancy is considered common in microbial systems, but recent studies have challenged this idea. The mechanism for this contradictory result is not clear. However, in this study, we hypothesize that strong environmental filtering which links to the anthropogenic activities is able to weaken microbial functional redundancy. We used metagenome and 16S rRNA gene high-throughput sequencing to investigate planktonic microbial communities in a subtropical river. We found that the weak anthropogenic activities might result in a low selection pressure in the river upstream area. Therefore, the microbial community functional attributes were stable although the community composition changed with the water temperature and NO₃-N in upstream area (this indicates functional redundancy). However, the strong anthropogenic activities in river downstream area selected pollutant-degraded functions (e.g. nitrogen metabolism, toluene, xylenes and ethylbenzene degradation) and potentially pollutant-degraded (tolerant) microbes, and therefore caused the microbial community composition synchronously changed with the variation of community functional attributes. Our results reveal that strong environmental filtering which associates with the anthropogenic activities not only has effects on microbial community composition and community functional attributes but also on their relationships. These results provide a new insight to refine the functional redundancy idea.     

Estimating Virus Production Rates in Aquatic Systems

Viruses are pervasive components of marine and freshwater systems, and are known to be significant agents of microbial mortality. Developing quantitative estimates of this process is critical as we can then develop better models of microbial community structure and function as well as advance our understanding of how viruses work to alter aquatic biogeochemical cycles. The virus reduction technique allows researchers to estimate the rate at which virus particles are released from the endemic microbial community. In brief, the abundance of free (extracellular) viruses is reduced in a sample while the microbial community is maintained at near ambient concentration. The microbial community is then incubated in the absence of free viruses and the rate at which viruses reoccur in the sample (through the lysis of already infected members of the community) can be quantified by epifluorescence microscopy or, in the case of specific viruses, quantitative PCR. These rates can then be used to estimate the rate of microbial mortality due to virus-mediated cell lysis.     

Predicting bacterial community assemblages using an artificial neural network approach

Understanding the interactions between the Earth's microbiome and the physical, chemical and biological environment is a fundamental goal of microbial ecology. We describe a bioclimatic modeling approach that leverages artificial neural networks to predict microbial community structure as a function of environmental parameters and microbial interactions. This method was better at predicting observed community structure than were any of several single-species models that do not incorporate biotic interactions. The model was used to interpolate and extrapolate community structure over time with an average Bray-Curtis similarity of 89.7. Additionally, community structure was extrapolated geographically to create the first microbial map derived from single-point observations. This method can be generalized to the many microbial ecosystems for which detailed taxonomic data are currently being generated, providing an observation-based modeling technique for predicting microbial taxonomic structure in ecological studies.     

Deposition and postdeposition mechanisms as possible drivers of microbial population variability in glacier ice

Glaciers accumulate airborne microorganisms year by year and thus are good archives of microbial communities and their relationship to climatic and environmental changes. Hypotheses have focused on two possible drivers of microbial community composition in glacier systems. One is aeolian deposition, in which the microbial load by aerosol, dust, and precipitation events directly determines the amount and composition of microbial species in glacier ice. The other is postdepositional selection, in which the metabolic activity in surface snow causes microbial community shifts in glacier ice. An additional possibility is that both processes occur simultaneously. Aeolian deposition initially establishes a microbial community in the ice, whereas postdeposition selection strengthens the deposition patterns of microorganisms with the development of tolerant species in surface snow, resulting in varying structures of microbial communities with depth. In this minireview, we examine these postulations through an analysis of physical–chemical and biological parameters from the Malan and Vostok ice cores, and the Kuytun 51 Glacial surface and deep snow. We discuss these and other recent results in the context of the hypothesized mechanisms driving microbial community succession in glaciers. We explore our current gaps in knowledge and point out future directions for research on microorganisms in glacial ecosystems.     

Changes in functional diversity of soil microbial community with addition of antibiotics sulfamethoxazole and chlortetracycline

Potential effects of antibiotics on agricultural soil microflora have recently become increasing concerns with antibiotic-contaminated biosolid now being used in agricultural land. However, changes of soil microbial community function caused by the antibiotic-associated disturbance are less addressed. This paper investigated the changes in microbial functional diversity by spiking sulfamethoxazole (SMX) and chlortetracycline (CTC) in a loam paddy soil and then incubating for 21 days. The dose-effect and time-dependent changes of antibiotic-associated disturbance on soil microbial community were analyzed with the soils sampled at 7 and 21 days using Biolog EcoPlate. At day 7 following treatment, SMX decreased functional diversity of soil microbial community, and the treatment of 100 mg SMX kg?1 dry soil had a significant inhibition of average well color development (AWCD) and Shannon index as compared to the control (p?相似文献   

Short-term plant species impact on microbial community structure in soils with long-term agricultural history

The goal of our study was to capture the short-term effects of individual plant species on an established microbial community in a soil with a well-defined agricultural history. Using biochemical and molecular techniques we quantified the effects of plant species on changes in the soil microbial community over an 8-week time-course. We conducted a greenhouse experiment using field soil from a site that was managed as a Zea mays monoculture for over 50 years. The conditioned soil provided a baseline from which changes in microbial community composition through the effects of newly introduced plants could be determined. Within a short time frame (8 weeks), introduced plants influenced the soil microbial community in ways unique to each plant. Some species (Fagopyrm esculentum and xTriticosecale spp.) resulted in an increase of total microbial community richness, diversity and the stimulation of new microbial species not associated with the legacy vegetation. Other plants (Vicia villosa and Lolium multiflorum) tended to reduce community diversity. We suggest root surface area is good general predictor of rhizosphere microbial community diversity, but in some cases other plant traits may have dominant influence on plant-induced changes in microbial community composition.