土壤微生物在植物获得养分中的作用

大量施用化肥是当今农业的一个重要特征。化肥为粮食增产做出了巨大贡献,同时也带来一系列问题,如土壤酸化、水体富营养化、温室气体排放、资源耗竭等,直接威胁着农业可持续发展。土壤微生物是陆地生态系统植物多样性和生产力的重要驱动者,直接参与了植物获得养分和土壤养分循环两个过程。因此,通过调控土壤微生物的功能,有望降低农业对化肥的过分依赖。介绍了共生固氮菌、菌根真菌和根际促生菌对植物获得养分能力的影响及其机制,分析了土壤微生物对土壤氮、磷循环的影响及其与土壤养分生物有效性、养分损失的关系。依据这些知识,提出了改善植物营养、降低化肥施用的土壤微生物途径。虽然大量试验已证明了土壤微生物在改善植物营养中的重要作用,但是大面积应用土壤微生物技术来改善植物营养还存在不少问题。随着以后对这方面研究的加强以及上述问题的不断解决,土壤微生物有望在降低化肥施用量和维持农业可持续发展中做出重要贡献。     

微生物菌肥在农业生产中的价值和应用

随着农业生产技术的提升，人们越来越注重利用高效的生物防治技术来预防农业病虫害，如微生物菌肥。通过有效施用微生物菌肥能促使植株生长、增加作物产量。但从目前微生物菌肥在农业生产中的应用现状来看，由于对微生物菌肥的常规应用方法不够熟悉，农户只认可NPK含量高的肥料，而忽略了长期利用化肥对土壤的破坏，微生物菌肥可以很好地弥补这一不足。尤其是在如今绿色农业可持续发展战略要求深入人心的背景下，微生物菌肥具有良好的发展前景，将成为未来肥料领域的重要成员。     

微藻三酰甘油合成途径及其最新研究进展

三酰甘油(triacylglycerols,TAGs)是动物、植物、微生物和微藻细胞主要的储藏性脂类,它可应用于食品、轻工业和生物燃料等方面,是一种新型可再生能源——生物柴油生产的重要原料。与高等油料作物相比,微藻具有光合作用效率高、生长速度快、油脂产量高、不占用农业耕地和适应多种生长环境等优势,是一种潜在的新型生物柴油生产原料。然而,目前人们对有机体,尤其是微藻细胞内TAG合成与积累的分子机制及细胞的代谢调控机制还知之甚少。对TAG合成的一系列重要过程,包括脂肪酸的合成,TAG生物合成的主要途径和旁路途径,以及与TAG合成相关的关键酶和重要基因等进行了综述,特别对微藻细胞中与TAG合成相关的关键基因的最新研究进展进行了总结,旨在更好地了解油脂代谢的调控途径,为最大限度地供应生物柴油的生产原料提供理论基础。     

根际微生物群落功能与调控的研究进展

根际微生物群落是随植物长期进化及地球生境变迁而形成的动态微生物系统。随着多组学技术的不断发展，人们对根际微生物群落结构与功能的研究日益深入。根际微生物群落中的功能微生物类群，如植物促生细菌、植物促生真菌等，通过与植物建立紧密的物质、能量与信息联系，参与植物激素合成、难溶营养物解离、生物固氮、微生物拮抗、生长因子供应等系列生物学过程，从而提高植物营养物质吸收与抗逆能力，为植物的健康和高效生长提供重要保障。这些微生物中的某些成员已被开发成微生物刺激剂，广泛应用于作物增产抗逆与农田地力提升。近年来，多学科的交叉融合为根际微生物群落结构-功能-调控策略的交互式研究提供新的机遇，推动了基于合成生物学与材料科学技术的合成微生物组的发展。尤其是在核心微生物互作方面，人工蛋白创制、磁性组装、生物炭强化等策略能够增强核心微生物与目标植物之间的物理连接作用，大幅提高合成微生物组的工作效率和稳定性，从而有效驱动作物增产增收，提高污染修复效率。因此，根际微生物群落结构、功能与调控的深入研究，必将为绿色农业发展提供不竭动力。     

絮凝微生物采收微藻的作用机制研究进展

微藻广泛分布于自然界,其易培养,生长快且应用价值高,普遍用于生物燃料、医学原料、优质食品源及畜牧养殖业等。近年来,通过对光生物反应器改造设计、高产藻株筛选、代谢通路基因改造等方法实现微藻产量的提高,而在微藻处理的下游过程的研究与创新不足,特别是微藻采收已经成为其产业发展的瓶颈。本文综述了絮凝法在微藻采收中的作用,重点讨论了絮凝微生物在微藻采收中的作用,并对絮凝微生物对微藻的絮凝机制进行广泛探讨,为絮凝微生物采收微藻提供理论依据。     

长期不同施肥制度下几种土壤微生物学特征变化

 为阐明土壤微生物对土壤健康的生物指示功能, 以国家褐潮土肥力与肥料效益监测基地的长期肥料试验为平台, 应用BIOLOG ECO微平板培养法与常规分析法研究了长期施肥15年后不同施肥制度对土壤微生物生物量、活性、群落代谢功能多样性及土壤肥力的影响。研究结果表明, 与对照(CK)相比, 长期化肥与有机肥配施土壤中土壤有机质(SOM)、全氮(STN)、全磷(STP)含量升高, 土壤C/N与pH值降低, 土壤微生物量碳(Soil microbial biomass carbon, SMBC)、生物微生物量氮(Soil microbial biomass nitrogen, SMBN)、微生物商(qMB)及脲酶(Urease)活性升高, BIOLOG ECO微平板平均颜色变化率(Average well color development, AWCD)、土壤微生物代谢功能多样性指数变化不明显。和长期单施化肥处理(NPK)相比, 长期化肥与有机肥配施处理中上述几种微生物学特征(SMBC、SMBN、qMB、Urease及AWCD、代谢功能多样性指数)均呈极显著增加。NPK处理与CK相比虽然SOM、STN、STP含量稍有升高, 土壤C/N与pH值降低, SMBC、SMBN、qMB及Urease活性增高, 但是AWCD、土壤微生物代谢功能多样性指数却显著下降。过氧化氢酶活性(Catalase)在各处理土壤中的差异不显著。土壤微生物碳源利用的主成分分析表明, 长期不同施肥各处理在土壤微生物利用碳源的种类和能力上有差异。此试验说明, 土壤微生物受农业管理措施和多种环境因素的影响, 土壤微生物学特征可作为土壤质量的敏感指标, 为提高作物产量、增强肥力提供理论参考。     

伊贝根际微生物

<正>土壤微生物是土壤中最活跃的因子,一方面是土壤天然有机体的转化者,另一方面是土壤养分的源和库,与植物营养和土壤肥力密切相关,在土壤物质和能量循环转化过程中起着重要作用。在植物的整个生长期间,根系进行着活跃的代谢作用,向根外不断分泌有机物质,这些分泌物是根际微生物的重要营养和能量来源,其成分和数量影响着根际微生物的种类和繁殖。根际微生物的数量、活性和群落结构及其变化直接影响到植物吸收水分和养分。因此,植物、土壤和微生物之间存在着相互依赖、相互作用的复杂的三边关系[1-2]。     

生物炭影响作物生长及其与化肥混施的增效机制研究进展

利用秸秆型生物炭进行还田改土不仅具有提升作物产量的潜力,而且能够产生明显的环境效益,现已成为当今国内外农业领域的研究热点.本文综述了近年来国内外有关生物炭添加影响作物生长的分子调控机制研究,尤其关注了生物炭与作物根系的互作效应;介绍了生物炭与化肥混施的生物学效应及可能的增效机制;展望了今后的研究方向,以期促进我国相关领域的研究.国内外的最新研究表明:生物炭土壤添加改善植物生长的关键是生长素相关信号转导分子,通过促进植物细胞扩增、细胞壁松弛、水及营养的转运等相关基因的表达,有利于植物的新陈代谢及生长.生物炭及其与根系的相互作用能够直接或间接地影响土壤物理、化学、生物因子,从而在炭、肥互作增效过程中起主导调控作用.     

微藻生物质产品和生物活性物质的研究与开发

本文综述了微藻在生物质产品及活性物质开发上的研究进展。部分微藻如节旋藻、小球藻、盐生杜氏藻和雨生红球藻等已用于商业化生产生物质产品。另外,从微藻中提炼的生物活性成分如β-胡萝卜素、虾青素、藻蓝蛋白、长链多不饱和脂肪酸和活性多糖等已应用于营养保健品和化妆品的生产。基于微藻种类的多样性和基因工程、代谢工程的快速发展,微藻天然产物具有很大的开发潜力。     

农业利用对海南省天然次生林土壤微生物的影响

为揭示天然次生林经过长期农业利用后土壤微生物学性质以及土壤养分状况的变异,采集了海南省天然次生林土壤以及由天然次生林经农业开垦转变而成的香蕉、桉树和橡胶林区表层土壤样品,利用磷脂脂肪酸(PLFA)分析、变性梯度凝胶电泳(DGGE)、群落水平生理特征(CLPP)分析等方法探究天然次生林经农业利用对土壤微生物生物量、微生物活性、群落多样性和功能多样性的影响。研究结果显示,天然次生林土壤总磷脂脂肪酸显著高于经农业利用的土壤,分别是香蕉和橡胶林土壤的3倍和2倍。平均颜色变化率(AWCD)以及由PLFA、DGGE和CLPP分析获得的土壤微生物群落多样性和功能多样性均显示出天然次生林高于农业利用的土壤。天然次生林土壤与农业利用土壤的微生物群落结构也存在明显的分异。另外,天然次生林土壤p H值、有机碳、总氮、总磷、速效氮和速效钾含量高于经农业利用的土壤。逐步回归分析显示土壤p H值、有机碳和速效氮是影响土壤微生物生物量、微生物活性、群落多样性和功能多样性的主要因素。研究结果表明,天然次生林经农业利用后,由于种植单一树种和农业管理措施可能造成土壤有机质和养分含量下降,导致土壤酸化,对土壤微生物群落造成负面影响。     

微生物降解秸秆木质素的研究进展

我国秸秆资源丰富，每年产生逾8亿t作物秸秆。通过秸秆直接还田或肥料化还田不仅可以减少化肥的施用量，缓解农业污染压力，还能实现农作物秸秆的循环利用。木质素结构复杂，且与纤维素和半纤维素相互缠绕，因此秸秆的自然腐解过程中，木质素是主要的限速因子，为了提高降解效率，木质素降解菌的发掘和降解机制也逐渐成为研究热点。本文综述了降解木质素的真菌和细菌的研究现状，对比其真菌和细菌降解特性的优缺点并分析复合降解菌群的优势。随后对木质素降解酶系的酶学性质、在不同微生物中的表达特性进行总结，对木质素降解机制及衍生芳烃代谢路径的研究进展进行综述。最后整理木质素降解微生物在秸秆肥料化技术中的应用进展，并探讨了微生物降解秸秆木质素的应用前景和未来的研究方向。     

Microalgae and Cyanobacteria: How Exploiting These Microbial Resources Can Address the Underlying Challenges Related to Food Sources and Sustainable Agriculture: A Review

For thousands of years, crop production has almost entirely depended on conventional agriculture. However, the reality is changing. The ever-growing population, global climate change, soil degradation and biotic/abiotic stresses are a growing threat to food production and security. Thus, sustainable alternatives to increase crop production for a population projected to reach 9.8 billion by 2050 are a major priority. In addition to vertical and soilless farming, innovative products based on bioresources, including plant growth stimulants, have been a target for sustainable food production. Such solutions have led to the exploitation of microorganisms, including microalgae and cyanobacteria as potential bioresources for food and plant biostimulant products. Microalgae (eukaryotic) and cyanobacteria (prokaryotic) are photosynthetic microorganisms with the capacity to synthesize a vast array of bioactive metabolites from atmospheric CO₂ and inorganic nutrients. The present review outlines the nutritional value of microalgae and cyanobacteria as alternative food resources. The potential aspects of microalgae and cyanobacteria as stabilizers of the net change in soil organic carbon (C) levels for reduced farmland degradation are also highlighted. The applications of microalgae and cyanobacteria as remedies for improved soil structure and fertility, and as enhancers of crop productivity and abiotic stress tolerance in agricultural settings are outlined. This review also discusses the co-cultivation of crops with microalgae or cyanobacteria in hydroponic systems to favor optimum root CO₂/O₂ levels for optimized crop production.

     

Soil microalgae and cyanobacteria: the biotechnological potential in the maintenance of soil fertility and health

Abstract

The soil microbiota plays a major role in maintaining the nutrient balance, carbon sink, and soil health. Numerous studies reported on the function of microbiota such as plant growth-promoting bacteria and fungi in soil. Although microalgae and cyanobacteria are ubiquitous in soil, very less attention has been paid on the potential of these microorganisms. The indiscriminate use of various chemicals to enhance agricultural productivity led to serious consequences like structure instability, accumulation of toxic contaminants, etc., leading to an ecological imbalance between soil, plant, and microbiota. However, the significant role of microalgae and cyanobacteria in crop productivity and other potential options has been so far undermined. The intent of the present critical review is to highlight the significance of this unique group of microorganisms in terms of maintaining soil fertility and soil health. Beneficial soil ecological applications of these two groups in enhancing plant growth, establishing interrelationships among other microbes, and detoxifying chemical agents such as insecticides, herbicides, etc. through mutualistic cooperation by synthesizing enzymes and phytohormones are presented. Since recombinant technology involving genomic integration favors the development of useful traits in microalgae and cyanobacteria for their potential application in improvement of soil fertility and health, the merits and demerits of various such advanced methodologies associated in harnessing the biotechnological potential of these photosynthetic microorganisms for sustainable agriculture were also discussed.     

Mechanisms of action of plant growth promoting bacteria

The idea of eliminating the use of fertilizers which are sometimes environmentally unsafe is slowly becoming a reality because of the emergence of microorganisms that can serve the same purpose or even do better. Depletion of soil nutrients through leaching into the waterways and causing contamination are some of the negative effects of these chemical fertilizers that prompted the need for suitable alternatives. This brings us to the idea of using microbes that can be developed for use as biological fertilizers (biofertilizers). They are environmentally friendly as they are natural living organisms. They increase crop yield and production and, in addition, in developing countries, they are less expensive compared to chemical fertilizers. These biofertilizers are typically called plant growth-promoting bacteria (PGPB). In addition to PGPB, some fungi have also been demonstrated to promote plant growth. Apart from improving crop yields, some biofertilizers also control various plant pathogens. The objective of worldwide sustainable agriculture is much more likely to be achieved through the widespread use of biofertilizers rather than chemically synthesized fertilizers. However, to realize this objective it is essential that the many mechanisms employed by PGPB first be thoroughly understood thereby allowing workers to fully harness the potentials of these microbes. The present state of our knowledge regarding the fundamental mechanisms employed by PGPB is discussed herein.     

Investigation of the Effects of Phosphate Fertilizer Application on the Heavy Metal Content in Agricultural Soils with Different Cultivation Patterns

The use of phosphate fertilizers is essential in agriculture, because they supply farmland with nutrients for growing plants. However, heavy metals might be included as impurities in natural materials and minerals, so heavy metals can also be present in phosphate fertilizers or other chemical fertilizers. The aim of this work was to assess the heavy metal content and contamination status of agricultural soils in the Hamadan province of Iran used for the cultivation of different crops, including cucumber, potatoes, and sugar beet. Surface soil samples were collected and analyzed to determine the total concentration of specific elements (As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn), before the pollution index was calculated for each element. Soils used for the cultivation of the three types of crop were not contaminated with As, Cr, Cu, Pb, or Zn. However, the pollution indices for Cd were 1.1, 4.4, and 3.8 in cucumber, potato, and sugar beet fields, respectively, which indicated moderate, high, and high levels of contamination, respectively. Soils from potato and sugar beet fields were heavily contaminated with Cd, which may have resulted from long-term overuse of phosphate fertilizers.     

Potentials of termite mound soil bacteria in ecosystem engineering for sustainable agriculture

The environmental deteriorating effects arising from the misuse of pesticides and chemical fertilizers in agriculture has resulted in the pursuit of eco-friendly means of producing agricultural produce without compromising the safety of the environment. Thus, the purpose of this review is to assess the potential of bacteria in termite mound soil to serve as biofertilizer and biocontrol as a promising tool for sustainable agriculture. This review has been divided into four main sections: termite and termite mound soils, bacterial composition in termite mound soil, the role of bacteria in termite mound soil as biofertilizers, and the role of bacteria in termite mound soil as biocontrol. Some bacteria in termite mound soils have been isolated and characterized by various means, and these bacteria could improve the fertility of the soil and suppress soil borne plant pathogens through the production of antibiotics, nutrient fixation, and other means. These bacteria in termite mound soils could serve as a remarkable means of reducing the reliance on the usage of chemical fertilizers and pesticides in farming, thereby increasing crop yield.     

Algae as Bio-fertilizers: Between current situation and future prospective

Bio-fertilization is a sustainable agricultural practice that includes using bio-fertilizers to increase soil nutrient content resulting in higher productivity. Soil micro-flora has been exposed to improve soil fertility and increase biomass productivity and identified as a correct environmentally friendly bio-based fertilizer for pollution-free agricultural applies. The majority of cyanobacteria can fix nitrogen from the atmosphere and several species including Anabaena sp., Nostoc sp., and Oscillatoria angustissima is known to be effective cyanobacterial based bio fertilizers. Acutodesmus dimorphus, Spirulina platensis Chlorella vulgaris, Scenedesmus dimorphus, Anabaena azolla, and Nostoc sp. are some of the green microalgae and cyanobacteria species that have been successfully used as bio fertilizers to boost crop growth. Also, Chlorella vulgaris is one of the most commonly used microalgae in bio fertilizer studies. The addition of seaweed species that are Sargassum sp. and Gracilaria verrucosa leads to chemical changes as a soil fertility indicator on clay and sandy soils, and the addition of seaweed conditioner to soil can improve its organic content, return pH to normal, and reduce C/N ratio in both sandy and clay soil. This review provides an effective approach to increase soil fertility via environmentally friendly bio-based fertilizer using micro and macro algae. Instead of the usage of inorganic and organic fertilizers that have polluted impacts to soil as aggregation of heavy metals, in addition to there their human carcinogenic effects.     

Plant–microbes interactions in enhanced fertilizer-use efficiency

The continued use of chemical fertilizers and manures for enhanced soil fertility and crop productivity often results in unexpected harmful environmental effects, including leaching of nitrate into ground water, surface run-off of phosphorus and nitrogen run-off, and eutrophication of aquatic ecosystems. Integrated nutrient management systems are needed to maintain agricultural productivity and protect the environment. Microbial inoculants are promising components of such management systems. This review is a critical summary of the efforts in using microbial inoculants, including plant growth-promoting rhizobacteria and arbuscular mycorrhizal fungi for increasing the use efficiency of fertilizers. Studies with microbial inoculants and nutrients have demonstrated that some inoculants can improve plant uptake of nutrients and thereby increase the use efficiency of applied chemical fertilizers and manures. These proofs of concept studies will serve as the basis for vigorous future research into integrated nutrient management in agriculture.     

Plant influence on nitrification

Modern agriculture has promoted the development of high-nitrification systems that are susceptible to major losses of nitrogen through leaching of nitrate and gaseous emissions of nitrogen oxide (NO and N2O), contributing to global warming and depletion of the ozone layer. Leakage of nitrogen from agricultural systems forces increased use of nitrogen fertilizers and causes water pollution and elevated costs of food production. Possible strategies for prevention of these processes involve various agricultural management approaches and use of synthetic inhibitors. Growing plants capable of producing nitrification suppressors could become a potentially superior method of controlling nitrification in the soil. There is a need to investigate the phenomenon of biological nitrification inhibition in arable crop species.     

有机类肥料对土壤养分含量的影响

绿色、可持续是我国发展现代农业的必然要求,肥料投入是关键之一。基于有机肥培肥土壤、生态友好的优势,发展和推广有机肥已经成为我国农业生产的一项基本国策。我国有机肥来源广泛、种类繁多,农业生产条件千差万别。本文分析了我国有机肥产品种类及标准现状、理化性质差异、碳氮矿化特性差异及影响因素,评述了施用有机肥对提高耕地基础地力的作用。因来源、制作工艺不同,不同有机肥的有机碳组分含量、全氮和活性氮含量、碳氮比等基本性质差异明显,这四者是影响有机肥碳氮矿化率、碳氮矿化量、碱解氮释放量等碳氮供应特性的主要内在因素;加之土壤环境等外界因素的影响,不同有机肥表现出不同的养分供应特性。总体上,有机肥一方面对提高土壤有机质含量,尤其是活性有机质含量和碳库管理指数效果明显,另一方面可增加土壤氮磷钾养分容量,减少作物生长消耗带来的土壤养分亏损,促进土壤质量良性发展。今后,应加强有机肥在耕地培肥中的应用,并加强有机肥肥效理论的基础研究和安全高效有机肥新产品的开发,促进有机肥资源的高效循环利用,使其成为重要的农业资源。