Interaction between microplastics and microorganisms in soil environment: a review / 生物工程学报

As a widespread pollutant in the environment, research on microplastics have attracted much attention. This review systematically analyzed the interaction between microplastics and soil microorganisms based on existing literatures. Microplastics can change the structure and diversity of soil microbial communities directly or indirectly. The magnitude of these effects depends on the type, dose and shape of microplastics. Meanwhile, soil microorganisms can adapt to the changes caused by microplastics through forming surface biofilm and selecting population. This review also summarized the biodegradation mechanism of microplastics, and explored the factors affecting this process. Microorganisms will firstly colonize the surface of microplastics, and then secrete a variety of extracellular enzymes to function at specific sites, converting polymers into lower polymers or monomers. Finally, the depolymerized small molecules enter the cell for further catabolism. The factors affecting this degradation process are not only the physical and chemical properties of the microplastics, such as molecular weight, density and crystallinity, but also some biological and abiotic factors that affect the growth and metabolism of related microorganisms and the enzymatic activities. Future studies should focus on the connection with the actual environment, and develop new technologies of microplastics biodegradation to solve the problem of microplastic pollution.

Effects of rumen microorganisms on the decomposition of recycled straw residue / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

Recently, returning straw to the fields has been proved as a direct and effective method to tackle soil nutrient loss and agricultural pollution. Meanwhile, the slow decomposition of straw may harm the growth of the next crop. This study aimed to determine the effects of rumen microorganisms (RMs) on straw decomposition, bacterial microbial community structure, soil properties, and soil enzyme activity. The results showed that RMs significantly enhanced the degradation rate of straw in the soil, reaching 39.52%, which was 41.37% higher than that of the control on the 30th day after straw return. After 30 d, straw degradation showed a significant slower trend in both the control and the experimental groups. According to the soil physicochemical parameters, the application of rumen fluid expedited soil matter transformation and nutrient buildup, and increased the urease, sucrase, and cellulase activity by 10%‒20%. The qualitative analysis of straw showed that the hydroxyl functional group structure of cellulose in straw was greatly damaged after the application of rumen fluid. The analysis of soil microbial community structure revealed that the addition of rumen fluid led to the proliferation of Actinobacteria with strong cellulose degradation ability, which was the main reason for the accelerated straw decomposition. Our study highlights that returning rice straw to the fields with rumen fluid inoculation can be used as an effective measure to enhance the biological value of recycled rice straw, proposing a viable solution to the problem of sluggish straw decomposition.

Biossólido no estabelecimento de espécies herbáceas e nos atributos químicos e microbiológicos em solo impactado pela mineração de carvão / Biosolids in the establishment of herbaceous species and in chemical and microbiological attributes in soil impacted by coal mining

RESUMO O presente estudo tem como objetivo avaliar o efeito da aplicação de diferentes concentrações de biossólido de lodo de esgoto, submetido a tratamento térmico, no estabelecimento de espécies herbáceas (aveia preta, ervilhaca e azevém) e nos atributos químicos e microbiológicos de um solo degradado pela mineração de carvão. O experimento foi instalado em área degradada pela mineração de carvão, localizada no munícipio de Treviso (SC), sendo os tratamentos compostos pelas concentrações de 0, 6,25, 100, 250 e 500 Mg ha-1 de biossólido, em parcelas de 2×2 m. Foram cultivadas espécies de aveia preta, ervilhaca e azevém de maneira consorciada, avaliando-se os parâmetros das plantas e os atributos químicos do solo nas profundidades 0-5, 5-10 e 10-20 cm. O biossólido proporcionou a elevação do pH do solo e o aumento dos teores disponíveis de P, K e carbono orgânico total e não influenciou na colonização micorrízica, na respiração basal do solo e na nodulação radicular. O uso do resíduo biossólido como substrato em áreas degradadas é uma alternativa para sua disposição final pela economia ao utilizá-lo como fertilizante, além dos benefícios ambientais, associados ao seu uso.

ABSTRACT This study aims to evaluate the effects of different concentrations of sewage sludge biosolid concentrations, submitted to thermal treatment, in the establishment of herbaceous species (black oats, vetches, and ryegrass) and in the chemical and microbiological attributes of a soil degraded by coal mining. The experiment was installed in an area degraded by coal mining, in Treviso/SC, with treatments composed of concentrations of 0; 6.25; 100; 250; and 500 Mg ha-1 of biosolids, in 2×2 m plots. Species of black oat, vetch, and ryegrass were grown in a consortium manner, evaluating the plant parameters and chemical attributes of the soil at depths 0-5, 5-10, and 10-20 cm. The biosolids provided improvements in soil fertility, such as pH elevation, increased levels available of P, K, and total organic carbon, in addition to not influencing mycorrhizal colonization, basal soil respiration, and root nodulation. The use of biosolid waste as a substrate in degraded areas is an alternative to its final disposal due to the economy when using it as a fertilizer, in addition to the environmental benefits associated with its use.

Correlation between rhizospheric microorganisms distribution and alkaloid content of Fritillaria taipaiensis / 中国中药杂志

In order to reveal the relationship between the amount of soil microorganisms and the quality of Fritillaria taipaiensis, both cultivated and wild F. taipaiensis were collected from Chongqing, Wuxi at different stages of their growth as objects of the research. The mycorrhizal infection rate and colonization intensity, peimisine and total alkaloid content in bulbs, the amount of microorganisms and biomass carbon content in rhizospheric soil were all determined using common methods. The results showed that the typical arbuscular-vesicle roots were formed after the AM fungi infected the F. taipaiensis roots which were collected from different origins. The mycorrhizal infection rates were ranged from 78.74% to 98.68% and the colonization intensities were ranged from 13.29% to 37.06%. The rhizospheric microorganisms of F. taipaiensis showed abundant resources. The distribution rule of them in the rhizospheric soil was as follows: the amount of bacteria>the amount of actinomycetes>the amount of fungi. The rhizospheric bacteria, decomposition inorganic phosphorus bacteria, decomposition organic phosphorus bacteria, actinomycetes amount and the total number of microbes increased first and then decreased with the increase of years, while decomposition potassium bacteria showed decreasing trend and fungi showed gradual increasing trend. The soil microbial flora content in the soil changed from "bacterial type" with a high fertility to "fungal type" with a low fertility. The mass fraction of peimisine and total alkaloid content increased first and then decreased with the increase of over the years, the same trend of culturable rhizosphere soil bacteria and actinomycetes indicated that the growth years affected the quality of soil and medicinal materials on different levels. Therefore, the diversity of microbial communities in rhizosphere soil reduced with the increase of years leading to the continuous cropping obstacles and the destruction of medicinal quality of F. taipaiensis.

Screening of polyketide genes from Brazilian Atlantic Forest soil / Evaluación de genes biosintéticos de policétidos provenientes de suelo de la selva atlántica brasileñae / Avaliação de genes biossintéticos de policetídeos provenientes do solo da Mata Atlântica Brasileira

Abstract Soil is a large source of microorganisms with potential to produce bioactive compounds. Since most of them cannot be cultured, metagenomics has become a useful tool in order to evaluate this potential. The aim of this study was to screen biosynthetic polyketide genes (PKS) present in a metagenomic library constructed from a soil sample isolated from the Brazilian Atlantic Forest. The library comprises 5000 clones with DNA inserts between 40 and 50 Kb. The characterization of the biosynthetic gene clusters of these molecules is a promising alternative to elucidate the biotechnological potential of bioactive compounds in microbial communities. The PKS genes were screened using degenerated primers. The positive clones for PKS systems were isolated, and their nucleotide sequences analysed with bioinformatics tools. The screening yielded two positive clones for PKS II genes. Furthermore, variations in the sequences of the PKS II genes from the metagenomic library were observed when compared with sequences of ketosynthases' databases. With these findings we gain insight into the possible relation between new biosynthetic genes and the production of new secondary metabolites.

Resumen El suelo es una fuente importante de microrganismos con potencial para producir compuestos bioactivos. Dado que la gran mayoría de estos microorganismos no puede cultivarse, la metagenómica se ha convertido en una herramienta útil para evaluar dicho potencial. El objetivo del presente estudio fue evaluar los genes biosintéticos de policétidos (PKS) presentes en una biblioteca metagenómica construida a partir de una muestra de suelo aislada de la selva atlántica brasileña. La biblioteca comprende 5000 clones con insertos de DNA entre 40 y 50 Kb. La caracterización de clústeres de genes biosintéticos de estas moléculas es una alternativa promisoria para elucidar el potencial biotecnológico de los compuestos bioactivos en comunidades microbianas. Los genes biosintéticos de PKS se evaluaron usando cebadores degenerados. Se aislaron los clones positivos para sistemas PKS y sus secuencias de nucleótidos se analizaron con herramientas bioinformáticas. La evaluación arrojó dos clones positivos para genes de PKS II. Además, se observaron variaciones en las secuencias de genes de PKS II de la biblioteca metagenómica cuando se compararon con las secuencias de las bases de datos de cetosintasas. Estos hallazgos proporcionan nueva información sobre la posible relación entre nuevos genes biosintéticos y la producción de nuevos metabolitos secundarios.

Resumo O solo é uma fonte de importante de microrganismos com potencial para produzir compostos bioativos. Considerando que a maioria destes microrganismos não se pode cultivar, a metagenômica tem se convertido em uma ferramenta útil para avaliar este potencial. O objetivo deste estudo foi avaliar os genes biossintéticos de policetídeos (PKS) presentes em uma biblioteca metagenômica construída a partir de uma amostra de solo isolada da Mata Atlântica brasileira. A biblioteca compreende 5000 clones com insertos de DNA entre 40 e 50 Kb. A caracterização de clusters de genes biossintéticos destas moléculas é uma alternativa promissora para elucidar o potencial biotecnológico de compostos bioativos em comunidades microbianas. Os genes PKS foram avaliados usando primers degenerados. Os clones positivos para sistemas PKS foram isolados e suas sequências de nucleotídeos foram analisadas com ferramentas de bioinformática. A avaliação forneceu dois clones positivos para genes PKS II. Além disso, variações nas sequências dos genes PKS II da biblioteca metagenômica foram observadas quando comparadas com sequências da base de dados de cetosintases. Com estas descobertas obtivemos uma visão sobre uma possível relação entre novos genes biossintéticos e a produção de novos metabólitos secundários.

Diversidade de fungos micorrízicos arbusculares em pomar orgânico no semiárido cearense / Diversity of arbuscular mycorrhizal fungi in an organic orchard of semi-arid land of Ceará, Brazil

The arbuscular mycorrhizal fungi (AMF) are key-organisms for maintenance of plant biodiversity in agroecosystems. There is an increasing interest in changes of the microbiological properties in the rhizosphere by its practical and environmental relevance. This research aimed to evaluate the occurrence of AMF in the establishment of fruits under organic management, and to compare them with an area of ​​native vegetation in semiarid Ceará. Soil samples were collected from 0-10cm layer in June, September and December 2010 in different areas. Number of spores, and diversity of AMF were quantified. The dominance of Glomus spores was confirmed in all the areas.

Os fungos micorrízicos arbusculares (FMA) são microrganismos chave na manutenção da biodiversidade de plantas em agroecossistemas e há o interesse no conhecimento sobre alterações nas propriedades microbiológicas do solo rizosférico pela sua relevância do ponto de vista prático e ecológico. Neste trabalho, objetivou-se avaliar a ocorrência de FMA na rizosfera de fruteiras em formação, sob o manejo orgânico, e compará-la com área de vegetação nativa no semiárido cearense. Amostras de solo foram coletadas da camada de 0-10cm em junho, setembro e dezembro de 2010 em áreas distintas nas linhas de plantio de fruteiras irrigadas. As amostras de solo foram submetidas a análises, em que quantificou-se o número de esporos e diversidade de FMA. A dominância de esporos do gênero Glomus foi confirmada na rizosfera das fruteiras e no solo sem interferência de plantas ou sob vegetação natural.

Influence of Allelochemicals on Microbial Community in Ginseng Cultivating Soil / 中草药·英文版

Objective: To study the influence of allelochemicals such as benzoic acid, diisobutyl phthalate, diisobutyl succinate, palmitic acid, and 2,2-bis-(4-hydroxyphenyl) propane on the microbial community of ginseng cultivating soil. Methods: Soil samples were sprayed with five allelochemicals (100 mg/L) and their mixture (20 mg/L), respectively. Carbon metabolic ability variances were analyzed by Biolog method and genetic polymorphism variance was analyzed by RAPD method. The Nei's genetic diversity index and Shannon's information index were calculated. Results: Significant differences in carbon metabolic activity were found between allelochemical-treated soils and control. Further analysis indicated that although the carbon-utilizing ability and genetic polymorphism of soils treated with di-isobutyl phthalate, di-isobutyl succinate, and allelochemical mixtures were lower than those of the other treatments, genetic similarities of soils treated with di-isobutyl phthalate, diisobutyl succinate, and allelochemical mixtures were much higher than those of the other treatments. Conclusion: Allelochemicals significantly declined the genetic diversity and carbon metabolic activity of microorganisms in newly reclaimed forest soil for ginseng cultivation.

Microbial Contributions in Alleviating Decline in Soil Fertility.

The continued decline in soil fertility, high fertilizer costs and the need to implement environmental friendly agricultural systems are some of the world’s major strategic concerns. Soil microorganisms are part of the soil ecosystem and are reported to contribute in soil fertility improvement. This paper is aimed at highlighting their contributions in alleviating soil fertility decline. The Rhizobium/legume symbiosis, a well known association contributes substantial amounts of biologically fixed nitrogen to cropping systems and significant benefits on yields of crops that follow in rotation. Soil microorganisms such as bacteria and fungi contribute to plant phosphorus nutrition through solubilization of sparingly soluble Al, Fe and Ca phosphates, and mineralization of phosphorus from organic substances. Solubilization is mainly achieved through production of organic acids, chelation and ligand exchange, and other pH lowering mechanisms whereas mineralization is achieved through production of enzymes such as phytases and phosphatases. Mycorrhizal associations are reported to contribute to plant phosphorus nutrition through increasing root surface area for soil exploration, production of phosphorus solubilizing enzymes and acids. Mycorrhizal fungi and bacteria also solubilize other nutrients such zinc, copper, potassium and calcium from their precipitated or sparingly soluble forms. Microorganisms also contribute to soil fertility improvement through their roles in composting. They are currently isolated, studied and packaged as biofertilizers and used to supplement chemical fertilizers. It can be noted that thorough exploitation of microbial activities can contribute to balanced plant nutrition. However, poor soil management practices limit realization of potential benefits from soil microorganisms whereas biofertilizer technology development in developing countries such as Sub-Saharan African countries is derailed because of lack of awareness, infrastructure and human capacity. From this study it can be noted that intensifying soil management practices that maximize microbial activities can go a long way in improving soil fertility with minimal use of chemical fertilizers. On the other hand there is a need to improve both human and infrastructure capacity in poor countries such as those in Sub-Saharan Africa so as to manage research in biofertilizer technologies. Awareness and dissemination of information on the importance of biofertilizers, intensifying effective microbial inoculation where it deemed to give good response and systematic evaluation of economic viability of biofertilizer technologies are other areas that need to be addressed.

Effect of Trichoderma longbrachiatum T2 on functional diversity of cucumber rhizomicrobes.

After biocontrol Trichoderma longbrachiatum T2 was applied in the rhizosphere of cucumber, the functional diversity of the rhizomicrobes utilizing carbon sources was investigated by using Biolog Eco-microplates technique. The result showed that T. longbrachiatum T2 had a significant effect on the rhizomicrobes in terms of their metabolic activity and their capacity to utilize carbon sources. The ability of the rhizomicrobes to utilize carbon sources was enhanced at seedling stage. The significant change of the richness and the degrees of the rhizomicrobes occured at seedling stage, flowering stage, and final stage, while no obvious difference was observed at fruiting stage. Principal Component Analysis (PCA) indicated that the ability of the rhizomicrobes to utilize carbon sources was enhanced at seedling stage and final stage. At flowering stage, the ability to utilize carbohydrates, amino acids, carboxylic acids, amines and phenolic compounds was reduced, but the ability to untilize polymers was slightly enhanced. The ability to utilize carbohydrates, amino acids, carboxylic acids, polymers and amines was enhanced, but the ability to utilize phenolic compounds was reduced at fruiting stage.

Isolamento e quantificação das populações de bactérias em geral e de actinomicetos presentes no solo / Aislamiento y cuantificación de poblaciones de bacterias en general y de actinomicetos presentes en el suelo / Isolation and quantification of actinomycetes and bacterial populations in general present in soil

O solo é um ecossistema complexo, dinâmico e difícil de ser estudado, a quantidade e diversidade de micro-organismos do solo são imensas. A microbiota do solo é caracterizada pela abundância e diversidade. A atividade microbiana é utilizada como uma maneira de melhor entender os processos de mineralização e observar mais profundamente a intensidade dos fluxos de energia no solo. A fertilidade natural do solo depende, portanto, da dinâmica de matéria orgânica e ciclagem de nutrientes, os quais são catalizados pela biomassa microbiana do solo. Dentre as bactérias existentes no solo, encontram-se as autotróficas, as heterotróficas, as aeróbias, as anaeróbias, as fixadoras de nitrogênio, nitrificantes e desnitrificantes, actinomicetos, entre outras. Estudos ecológicos das populações de actinomicetos são de extrema importância, visto que esses micro-organismos se destacam pela possibilidade de sintetizar vitaminas, substâncias inibidoras da atividade enzimática e antibióticos. A determinação das densidades populacionais na comunidade microbiana dos solos é importante, tanto na identificação de fatores que influenciam o equilíbrio microbiológico dos solos, como na caracterização das relações entre grupos e espécies de microrganismos. Portanto, é de grande relevância a quantificação das bactérias em geral e actinomicetos presentes no solo para que se possa inferir sobre a fertilidade do solo. Estudos dessa natureza podem fornecer subsídios para programas de conservação de áreas florestadas e recuperação de áreas degradadas.

Soil is a complex, dynamic and hard-to-study ecosystem due to the immense quantity and diversity of microorganisms. Soil microbiota is characterized by abundance and diversity. Microbial activity is used as a way to better understand the mineralization processes and have an in-depth visualization of the intensity of energy flows in the soil. The natural fertility of the ground depends, therefore, on the dynamics of organic matter and nutrient recycling, which are catalyzed by the soil microbial biomass. Among the bacteria on the soil, it is possible to find autotrophic, heterotrophic, aerobial, anaerobial, nitrogen-fixing, nitrifying and denitrifying, actinomycetes, and others. Ecological studies of actinomycete populations are of extreme importance, since these microorganisms are outstanding due to their ability to synthesize vitamins, enzymatic activity inhibitors and antibiotics. Determining microbial population densities is important both in the identification of factors which influence the microbiological balance in the soil and in the characterization of relationships among groups and species of microorganisms. Therefore, the quantification of bacteria in general and actinomycetes from the soil is of great importance, since it may enable inferences about soil fertility. Studies of this nature may provide subsidies for conservational programs in forested areas and degraded areas in recovery processes.

El suelo es un ecosistema complejo, dinámico y difícil de ser estudiado, ya que la cantidad y diversidad de microorganismos del suelo son inmensas. La microbiota del suelo se caracteriza por la abundancia y diversidad. La actividad microbiana es utilizada como una forma de entender mejor los procesos de mineralización y visualizar más profundamente la intensidad de los flujos de energía en el suelo. La fertilidad natural del suelo depende, por lo tanto, de la dinámica de materia orgánica y ciclo de nutrientes, los cuales son catalizados por la biomasa microbiana del suelo. Entre las bacterias existentes en el suelo, se encuentran los autótrofos, heterótrofos, aérobicos, anaeróbicos, fijadoras de nitrógeno, nitrificadoras y denitrificadoras, actinomicetos, entre otros. Estudios ecológicos de las poblaciones de actinomicetos son de extrema importancia, ya que esos microorganismos se destacan por la posibilidad de sintetizar vitaminas, sustancias inhibidoras de la actividad enzimática y antibióticos. La determinación de las densidades poblacionales en la comunidad microbiana de los suelos es importante, tanto en la identificación de factores que influencian el equilibrio microbiológico de los suelos, como la caracterización de las relaciones entre grupos y especies de microorganismos. Por lo tanto, es de gran importancia la cuantificación de las bacterias en general y actinomicetos presentes en el suelo para que se pueda inferir sobre la fertilidad del suelo. Estudios de esta naturaleza pueden proporcionar subsidios para programas de conservación de áreas forestales y recuperación de áreas degradadas.

Pathogenic and enzyme activities of the entomopathogenic fungus Tolypocladium cylindrosporum (Ascomycota: Hypocreales) from Tierra del Fuego, Argentina

Tolypocladium cylindrosporum is an entomopathogenic fungi that has been studied as a biological control agent against insects of several orders. The fungus has been isolated from the soil as well as from insects of the orders Coleoptera, Lepidoptera, Diptera and Hymenoptera. In this study, we analyzed the ability of a strain of T. cylindrosporum, isolated from soil samples taken in Tierra del Fuego, Argentina, to produce hydrolytic enzymes, and to study the relationship of those activities to the fungus pathogenicity against pest aphids. We have made the traditional and molecular characterization of this strain of T. cylindrosporum. The expression of hydrolase activity in the fungal strain was estimated at three incubation temperatures (4ºC, 12ºC and 24ºC), on different agar media supplemented with the following specific substrates: chitin azure, Tween ® 20, casein, and urea for chitinase, lipase, protease, and urease activity, respectively. The hydrolytic-enzyme activity was estimated qualitatively according to the presence of a halo of clarification through hydrolase action, besides was expressed semi-quantitatively as the ratio between the hydrolytic-halo and colony diameters. The pathogenicity of the fungus was tested on adults of the aphid Rhopalosiphum padi at three temperatures of incubation (4ºC, 12ºC and 24ºC). The suspension was adjusted to a concentration of 1x10 7 conidia/ml. In pathogenicity assays at seven days post-inoculation, the fungus caused the mortality of adults of Ropalosiphum padi at different temperatures also showed a broad ability to grow on several agar-culture media, supplemented with different carbon sources at the three incubation temperatures tested. Although, the growth was greater with higher incubation temperatures (with maximum levels at 24°C), the fungus reached similar colony diameters after 15 days of incubation on the medium supplemented with Tween® 20 at the lower two incubation temperatures of 4°C or 12°C. In accordance with the results on colony diameters, the fungus revealed an ability to degrade casein, chitin derivatives, Tween® 20, and urea as evidenced by the appearance of a halo around the fungal colony. Because of its origin and temperature tolerance, this Argentine strain has great potential for use as a biocontrol agent for insect pest control in cold and temperate environments. Rev. Biol. Trop. 60 (2): 833-841. Epub 2012 June 01.

El hongo entomopatógeno Tolypocladium cylindrosporum ha sido estudiado como un agente de control biológico contra insectos de varios órdenes. Esta especie fue aislada del suelo, así como de insectos de los órdenes Coleoptera, Lepidoptera, Diptera e Hymenoptera. En el presente trabajo hemos analizado la capacidad de una cepa de T. cylindrosporum (LPSC Nº1065) aislada del suelo en Tierra del Fuego, Argentina, para producir enzimas hidrolíticas y determinar la relación de esta actividad con la patogenicidad del hongo para combatir la plaga de los áfidos en diferentes temperaturas (4º, 12º y 24ºC). En los ensayos de patogenicidad, siete días posteriores a la inoculación, se registró mortalidad en los adultos del áfido Ropalosiphum padi a diferentes temperaturas y también se demostró una amplia capacidad de crecer en varios medios de cultivos complementados con diferentes fuentes de carbono bajo las tres temperaturas de incubación ensayadas. Debido a su origen y a la tolerancia que tiene a bajas temperaturas esta cepa, presenta un gran potencial para su uso como agente de control biológico para las plagas de insectos de ambientes fríos y templados.

Soil microbial biomass in organic farming system / Biomassa microbiana do solo em sistemas orgânicos

Agricultural production systems have to combine management practices in order to sustain soil's profitability and quality. Organic farming is gaining worldwide acceptance and has been expanding at an annual rate of 20 percent in the last decade, accounting for over 24 million hectares worldwide. Organic practices avoid applications of synthetic fertilizers and pesticides, rely on organic inputs and recycling for nutrient supply, and emphasize cropping system design and biological processes for pest management, as defined by organic farming regulation in the world. In comparison with conventional farming, organic farming has potential benefits in improving food quality and safety. Plant production in organic farming mainly depends on nutrient release as a function of mineralization processes in soils. The build-up of a large and active soil microbial biomass is important pool of accessible nutrients, therefore, is an important priority in organic farming. In organic farming, there is positive effect of quantity and quality of inputs of organic residues on soil microbial biomass. In this way, the organic systems are extremely important for the increase of the soil fertility and the maintenance of the environmental sustainability.

A produção agrícola tem de combinar práticas para prover a sustentabilidade do solo. A agricultura orgânica está ganhando aceitação mundial e cresce à taxa anual de 20 por cento na última década, contabilizando mais de 24 milhões de hectares. As práticas orgânicas evitam o uso de fertilizantes sintéticos e pesticidas, enfatiza a aplicação de matéria orgânica, como também a reciclagem de nutrientes e de processos biológicos para manejo de pragas, através das regras dos sistemas orgânicos no mundo. Em comparação com a agricultura convencional, os sistemas orgânicos têm potencial de melhorar a qualidade e a segurança dos alimentos. A produção das plantas no sistema orgânico depende da liberação de nutrientes pelo processo de mineralização microbiana no solo. A construção de uma grande e ativa biomassa microbiana é um importante reservatório de nutrientes disponíveis. Dessa forma, isso é uma prioridade no sistema orgânico. Em sistemas orgânicos, há efeitos positivos da quantidade e da qualidade das fontes de carbono orgânico sobre a biomassa microbiana do solo. Nesse sentido, as práticas do sistema orgânico são extremamente importantes para o aumento da fertilidade do solo e para a manutenção da sustentabilidade ambiental.

Transformação genética e aplicação de glifosato na microbiota do solo, fixação biológica de nitrogênio, qualidade e segurança de grãos de soja geneticamente modificada / Genetic transformation and the use glyphosate on soil microbial, biological nitrogen fixation, quality and safety of genetically modified soybean

A soja geneticamente modificada resistente ao herbicida glifosato (GM RR) é o principal produto da biotecnologia vegetal, considerando-se a evolução da área cultivada e o consumo desse grão. Os Estados Unidos, a Argentina e o Brasil são os maiores produtores de soja GM RR. A liberação para cultivo da soja GM RR no Brasil foi efetivada com base, quase que exclusivamente, em trabalhos realizados em outros países, sem a devida validação nas condições edafoclimáticas locais. Nesse contexto, buscou-se coletar e analisar os principais trabalhos que versam sobre impacto ambiental, metabolismo da planta, qualidade e segurança da soja GM RR tratada e não tratada com glifosato. De modo geral, os trabalhos analisados apresentam algumas características comuns: a) avaliam poucas variáveis; e b) inferem, a partir de simulação com ensaios em casa de vegetação ou in vitro, possíveis respostas no cultivo comercial. Embora ainda escassos, os estudos realizados apontam para o fato de que a transformação genética não afeta os microrganismos do solo, nem a fixação biológica de nitrogênio, nem a composição dos grãos. O fator que pode afetar essas variáveis é a aplicação do glifosato no controle de plantas daninhas, ou seja, os riscos de perigo ao ambiente e à segurança dos produtos derivados dessa matéria-prima se devem ao insumo aplicado durante o cultivo, e não à transformação genética propriamente dita.

The genetically modified soybean resistant to glyphosate (GM RR) is the main product of plant biotechnology, considering the evolution of the area cultivated and the use of this grain. EUA, Argentina and Brazil are the largest producers of GM RR. The release of GM RR soybean cultivation in Brazil was done based on researches that were accomplished in other countries without the validation of the same edaphoclimatic conditions. In this context, the main researches about environmental impact, plant metabolism, quality and safety of GM RR soybean with or without glyphosate application were collected and investigated. In general, the researches investigated showed some similar characteristics: a) few variables were studied; b) simulations in green house or in vitro are used to infer possible response on the field. Although scarce, the researches denoted that the genetic transformation did not affect soil microorganisms, biological nitrogen fixation and composition of grains. The factor which could affect these variables is the glyphosate application in weed control, thus the risk of damage to the environment and the safety of products derived from this raw materialare due to the use of the herbicide during cultivation, and not to the genetic transformation. Key words: Transgenic soybean, soil microorganisms, herbicides residue, isoflavones.

The Dynamic Changes of Soil Beneficial Bacteria in Cotton Continuous Cropping Soil South Xinjiang / 微生物学通报

To research the effect of continuous cropping on cotton soil microorganisms and soil microorgan-isms on grow of cotton,we studied the total numbers of aerobic self-nitrogen-fixing bacteria,potassium bacteria,cellulose decomposing bacteria,phosphate solubilizing bacteria,organic-phosphorus-dissolving bacteria distributed in continuous cropping cotton fields of regimental farm 2 and 3 of the first agricultural division through dilution spread plate method.Results showed that the total numbers of five kinds of bacte-ria was highest in blooming and bolling periods,lowest in seeding periods and higher in before sowing pe-riods.The total numbers of five kinds of bacteria was no notable regular changes with continuous cropping year.The numbers of aerobic self-nitrogen-fixing bacteria at different cotton growth stages in regimental farm 2 was higher than in regimental farm 3 and the numbers change of other bacteria was varied in different cotton growth stages in regimental farm 2 and 3.Soil beneficial bacteria were negatively correlated with a variety of soil nutrient ion and free-living nitrogen fixing bacteria were significantly positive correlated with soil total nitrogen.

Metagenomics:New Strategy for Soil Microbiology Research / 微生物学通报

Most of the soil microorganisms are unculturable,which limits the exploitation and application of microbial resources.Metagenomics has great potential in the research of unculturable microorganisms in soil.Progress on the research of metagenomic DNA purification,metagenomic library construction and screening of soil microorganisms are reviewed briefly.