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The microbial nitrogen cycle

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889194124 Year: Pages: 174 DOI: 10.3389/978-2-88919-412-4 Language: English
Publisher: Frontiers Media SA
Subject: Microbiology --- Science (General)
Added to DOAB on : 2015-12-10 11:59:06
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Nitrogen is an essential element in biological systems, and one that often limits production in both aquatic and terrestrial systems. Due to its requirement in biological macromolecules, its acquisition and cycling have the potential to structure microbial communities, as well as to control productivity on the ecosystem scale. In addition, its versatile redox chemistry is the basis of complex biogeochemical transformations that control the inventory of fixed nitrogen, both in local environments and over geological time. Although many of the pathways in the microbial nitrogen cycle were described more than a century ago, additional fundamental pathways have been discovered only recently. These findings imply that we still have much to learn about the microbial nitrogen cycle, the organisms responsible for it, and their interactions in natural and human environments. Progress in nitrogen cycle research has been facilitated by recent rapid technological advances, especially in genomics and isotopic approaches. In this Research Topic, we reviewed the leading edge of nitrogen cycle research based on these approaches, as well as by exploring microbial processes in modern ecosystems.

Physiological and molecular ecology of aquatic cyanobacteria

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889193189 Year: Pages: 127 DOI: 10.3389/978-2-88919-318-9 Language: English
Publisher: Frontiers Media SA
Subject: Microbiology --- Oceanography --- Science (General)
Added to DOAB on : 2016-02-05 17:24:33
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The cyanobacteria inhabit every illuminated environment on Earth, from polar lakes to desert crusts and through their phototrophic metabolism play essential roles in global geochemical cycles. With the discovery of marine Synechococcus and Prochlorococcus almost 30 years ago, cyanobacteria have now earned their place as dominant primary producers contributing over 25 percent of global photosynthesis. Their global abundance is now explained from the coexistence of ecotypes that occupy different niches along spatial and temporal gradients. New ecotypes of Synechococcus have been identified as abundant components of microbial communities in freshwater environments and marginal seas. Extensive comparative genomics of marine and freshwater picocyanobacteria have begun to unmask adaptations to light and nutrient (N, P, Fe) limitation that these diverse environments present. Novel types of cyanobacterial diazotrophy input new N and structure microbial communities in the open sea. Current challenges include the understanding of the interactions between marine cyanobacteria and other microbes in their immediate community. In contrast, mesotrophic and eutrophic environments such as the Laurentian Great Lakes have been increasingly affected by nuisance and toxic cyanobacterial blooms that have yielded severe declines in water quality. Factors promoting bloom formation and the functional roles of toxins are important issues being addressed today.

Microbial Ecology of Arid Terrestrial Systems

Authors: --- ---
Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889199693 Year: Pages: 127 DOI: 10.3389/978-2-88919-969-3 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Microbiology
Added to DOAB on : 2016-01-19 14:05:46
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Water is usually referred to as the ‘Molecule of Life’. It constitutes the most abundant molecule in living (micro)organisms and is also essential for critical biochemical reactions, both for the global functioning and maintenance of Ecosystems (e.g., Photosynthesis) and individual (microbial) cells (e.g., ATP hydrolysis). However, most of Earth’s terrestrial environments present deficiencies in bioavailable water. Arid environments cover around a third of the land’s surface, are found on the six continents and, with the anthropogenic desertification phenomenon, will increase. Commonly defined by having a ratio of precipitation to potential evapotranspiration (P/PET) below 1, arid environments, being either hot or cold, are characterized by scant and erratic plant growth and low densities in macro-fauna. Consequently, these ecosystems are microbially mediated with microbial communities particularly driving the essential Na and C biogeochemical cycles. Due to the relatively simple trophic structure of these biomes, arid terrestrial environments have subsequently been used as ideal ecosystems to capture and model interactions in edaphic microbial communities. To date, we have been able to demonstrate that edaphic microorganisms (i.e., Fungi, Bacteria, Archaea, and Viruses) in arid environments are abundant, highly diverse, different from those of other terrestrial systems (both in terms of diversity and function), and are important for the stability and productivity of these ecosystems. Moreover, arid terrestrial systems are generally considered Mars-like environments. Thus, they have been the favored destination for astro(micro)biologists aiming to better understand life’s potential distribution and adaptation strategies in the Universe and develop terraforming approaches. Altogether, these points demonstrate the importance of significantly improving our knowledge in the microbial community composition (particularly for Fungi, Archaea and Viruses), assembly processes and functional potentials of arid terrestrial systems, as well as their adaptation mechanisms to aridity (and generally to various other environmental stresses). This Research Topic was proposed to provide further insights on the microbial ecology of hot and cold arid edaphic systems. We provide a detailed review and nine research articles, spanning hot and cold deserts, edaphic, rhizospheric, BSC and endolithic environments as well as culture-dependent and -independant approaches.

Ethylene's Role in Plant Mineral Nutrition

Authors: --- ---
Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889199464 Year: Pages: 151 DOI: 10.3389/978-2-88919-946-4 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Botany
Added to DOAB on : 2016-01-19 14:05:46
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Terrestrial plants are sessile organisms that, differently from animals, can not move in searching of the nutrients and water they need. Instead, they have to change continuously their physiology and morphology to adapt to the environmental changes. When plants suffer from a nutrient deficiency, they develop physiological and morphological responses (mainly in their roots) aimed to facilitate the acquisition and mobilization of such a nutrient. Physiological responses include some ones like acidification of the rizhosphere and release of chelating agents into the medium; and morphological responses include others, like changes in root architecture and development of root hairs. The regulation of these responses is not totally known but in the last years different plant hormones and signaling substances, such as auxin, ethylene, cytokinins and nitric oxide, have been involved in their control. Besides hormones, oxidative stress has also been related with most of the nutrient deficiencies. The relationship of ethylene with the regulation of responses to nutrient deficiencies came from the nineties, when some works presented data suggesting its involvement in the regulation of responses to Fe and P deficiency. In the last years, the role of ethylene has been extended to many other nutrient deficiencies, such as K deficiency, Mg deficiency, S deficiency, N deficiency, and others. In most of the cases, it has been found that ethylene production, as well as the expression of ethylene synthesis genes, increases under these nutrient deficiencies. Furthermore, it has also been found that ethylene controls the expression of genes related to responses to different deficiencies. The involvement of ethylene in so many deficiencies suggests that it should act in conjunction with other signals that would confer nutrient-specificity to the distinct nutrient responses. These other signals could be plant hormones (auxin, cytokinins, etc) as well as other substances (nitric oxide, microRNAs, peptides, glutathione, etc), either originated in the roots or coming from the shoots through the phloem. The role of ethylene in the mineral nutrition of plants is even more complex that the one related to its role in the responses to nutrient deficiencies. Ethylene has also been implicated in the N2 fixation of legume plants; in salt tolerance responses; and in responses to heavy metals, such as Cd toxicity. All these processes are related to ion uptake and, consequently, are related to plant mineral nutrition. We consider a good opportunity to review all this information in a coordinated way. This Research Topic will provide an overview about the role of the plant hormone ethylene on the regulation of physiological and morphological responses to different nutrient deficiencies. In addition, it will cover other aspects of ethylene related to plant nutrition such as its role on salinity, N2 fixation and tolerance to heavy metals.

Keywords

Boron --- ethylene --- heavy metals --- Iron --- Nitrogen --- nodulation --- Phosphate --- Potassium --- Salinity --- Sulfur

Linking Ecosystem Function to Microbial Diversity

Authors: ---
Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889199853 Year: Pages: 159 DOI: 10.3389/978-2-88919-985-3 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Oceanography --- Microbiology
Added to DOAB on : 2016-01-19 14:05:46
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Understanding the link between microbial diversity and ecosystem processes is a fundamental goal of microbial ecologists, yet we still have a rudimentary knowledge of how changes in diversity affect nutrient cycling and energy transfer in ecosystems. Due to the complexity of the problem, many published studies on this topic have been conducted in artificial or manipulated systems. Although researchers have begun to expose some possible mechanisms using these approaches, most have not yet been able to produce conclusive results that relate directly to natural systems. The few studies that have explored the link between diversity and activity in natural systems have typically focused on specific nutrient cycles or processes, such as nitrification, denitrification, and organic carbon degradation pathways, and the microbes that mediate them. What we have learned from these studies is that there are often strong associations between the physical and chemical features of the environment, the composition of the microbial communities, and their activities, but the rules that govern these associations have not been fully elucidated. These earlier studies of microbial diversity and processes in natural systems provide a framework for additional studies to broaden our understanding of the role of microbial diversity in ecosystem function. The problem is complex, but with recent advances in sequencing technology, -omics, and in-situ measurements of ecosystem processes and their applications to microbial communities, making direct connections between ecosystem function and microbial diversity seems more tractable than ever.

Geomicrobes: Life in Terrestrial Deep Subsurface

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Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889451791 Year: Pages: 141 DOI: 10.3389/978-2-88945-179-1 Language: English
Publisher: Frontiers Media SA
Subject: Microbiology --- Science (General)
Added to DOAB on : 2017-08-28 14:01:09
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The deep subsurface is, in addition to space, one of the last unknown frontiers to human kind. A significant part of life on Earth resides in the deep subsurface, hiding great potential of microbial life of which we know only little. The conditions in the deep terrestrial subsurface are thought to resemble those of early Earth, which makes this environment an analog for studying early life in addition to possible extraterrestrial life in ultra-extreme conditions. Early microorganisms played a great role in shaping the conditions on the young Earth. Even today deep subsurface microorganisms interact with their geological environment transforming the conditions in the groundwater and on rock surfaces. Essential elements for life are richly present but in difficultly accessible form. The elements driving the microbial deep life is still not completely identified. Most of the microorganisms detected by novel molecular techniques still lack cultured representatives. Nevertheless, using modern sequencing techniques and bioinformatics the functional roles of these microorganisms are being revealed. We are starting to see the differences and similarities between the life in the deep subsurface and surface domains. We may even begin to see the function of evolution by comparing deep life to life closer to the surface of Earth. Deep life consists of organisms from all known domains of life. This Research Topic reveals some of the rich diversity and functional properties of the great biomass residing in the deep dark subsurface.

Tropical Forest Ecosystem Responses to Increasing Nutrient Availability

Authors: --- --- ---
Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889452279 Year: Pages: 109 DOI: 10.3389/978-2-88945-227-9 Language: English
Publisher: Frontiers Media SA
Subject: Geography --- Science (General)
Added to DOAB on : 2017-10-13 14:57:01
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Deforestation and land use change have led to a strong reduction of tropical forest cover during the last decades. Climate change will amplify the pressure to the remaining refuges in the next years. In addition, tropical regions are facing increasing atmospheric inputs of nutrients, which will have unknown consequences for the structure and functioning of these systems, no matter if they are within protected areas or not. Even remote areas are expected to receive rising amounts of nutrients. The effects of higher rates of atmospheric nutrient deposition on the biological diversity and ecosystem functioning of tropical ecosystems are poorly understood and our knowledge of nutrient fluxes and nutrient limitation in tropical forest ecosystems is still limited. Yet, it will be of paramount importance to know the effects of increased nutrient availability to conserve these ecosystems with their biological and functional diversity. During the last years, research efforts have more and more focused on the understanding of the role of nutrients in tropical ecosystems and several coordinated projects have been established that study the effects of experimental nutrient addition. This Research Topic combines results from experiments and from observational studies with the aim to review and conclude on our current knowledge on the role of additional nutrients in ecosystems.

Microwave Based Weed Control and Soil Treatment

Authors: --- --- --- --- et al.
ISBN: 9783110605570 Year: Pages: 185 DOI: 10.1515/9783110605570 Language: English
Publisher: De Gruyter
Subject: Agriculture (General) --- General and Civil Engineering
Added to DOAB on : 2018-11-14 18:42:56
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Herbicide resistance has become an important constraint on modern agricultural practices. An alarming increase in weed biotypes that are resistant to herbicides has also been reported. Opportunity exists for a novel weed management technology, which is also compatible with no-till agricultural practices. Microwave heating can kill both emerged weed plants and weed seeds in the soil. When the intensity of the microwave fields is moderate, plants, which have already emerged, are susceptible to microwave treatment. If the microwave field is intense enough, very rapid volumetric heating and some thermal runaway in the plant structures cause micro-steam explosions in the plant cells, which rupture the plant structures, leading to death. Soil treatment requires significantly more energy however, there are secondary benefits for crops growing in microwave treated soil. These include: significant reduction of the dormant weed seed bank significant reduction of nematode populations significant reduction of fungal populations better availability of indigenous nitrogen for the plants more rapid humification and significant increases in crop growth and yield. Microwave weed management and soil treatment is not restricted by weather conditions therefore, the technology may offer some timeliness and environmental benefits, which are yet to be quantified in a cropping system.

Optimizing Miscanthus for the Sustainable Bioeconomy: From Genes to Products

Authors: --- ---
Book Series: Frontiers Research Topics ISSN: 16648714 ISBN: 9782889455669 Year: Pages: 230 DOI: 10.3389/978-2-88945-566-9 Language: English
Publisher: Frontiers Media SA
Subject: Science (General) --- Botany
Added to DOAB on : 2019-01-23 14:53:43
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In this Research Topic we report advances in fundamental and applied aspects of the perennial C4 bioenergy crop Miscanthus (Miscanthus spp.) and its role in mitigating climate change as part of the bioeconomy. Miscanthus is extremely well suited for bioenergy, biofuel and bioproduct production over a wide geographic area including Europe and North America as well as its native Asia.

Miscanthus offers a unique perspective within plant science: the challenge is to domesticate this novel crop for diverse environments and uses while simultaneously developing sustainable value chains to displace fossil fuels and contribute to climate change mitigation. Contributions to this Research Topic were offered from leading Miscanthus researchers from different parts of the world. We accepted 16 articles from 95 authors, which have generated 21,161 views at March 26 2018. Nine of the articles are the output of the European FP7 OPTIMISC project and describe multiple experiments investigating a common set of Miscanthus genotypes in Europe and Asia. These papers are complemented by seven additional articles from global authors, providing a comprehensive analysis of the state of the art of Miscanthus research and application.

Les légumineuses pour des systèmes agricoles et alimentaires durables

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ISBN: 9782759223350 9782759223367 Year: Pages: 512 DOI: 10.35690/978-2-7592-2335-0 Language: French
Publisher: éditions Quae
Subject: Environmental Technology
Added to DOAB on : 2019-09-13 11:21:04
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What do we know about inputs and potential of legumes in terms of the sustainability of agricultural and food systems? How can they be used to reduce the damage and maximise the benefits for the environment, agriculture and man? This reference work fuels the reflection on protein sources, nitrogen management in France and the relationship between legumes and sustainability.&#xD;

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