Soil Nitrogen Ecology (Soil Biology, 62)

Preface
Contents
Part I: Nitrogen Physiology and Ecology
	Chapter 1: Physiology and Distribution of Nitrogen in Soils
		1.1 Introduction
		1.2 Inorganic and Organic Forms of Nitrogen
			1.2.1 Inorganic N Compounds in Soils
				1.2.1.1 Nitrate
				1.2.1.2 Nitrite
				1.2.1.3 Ammonium
				1.2.1.4 Exchangeable NH4+
				1.2.1.5 Non-Exchangeable NH4+
				1.2.1.6 Dinitrogen Gas (N2) and Nitrous Oxide (N2O)
			1.2.2 Organic N Compounds in Soil
				1.2.2.1 Amino Acids in Soils
				1.2.2.2 Amino Sugars in Soils
				1.2.2.3 Nucleic Acid Bases in Soils
		1.3 Nitrogen Distribution
		1.4 Nitrogen Cycle
			1.4.1 Nitrogen Fixation
				1.4.1.1 Biological Nitrogen Fixation
				1.4.1.2 Industrial Nitrogen Fixation
			1.4.2 Nitrogen Mineralization
			1.4.3 Immobilization
			1.4.4 Nitrification
				1.4.4.1 Diversity of Nitrifying Bacteria in Soil
		1.5 Influence of C/N Ratio
		1.6 Losses of Nitrogen from Soil
			1.6.1 Ammonia Volatilisation
			1.6.2 Emission of N2O and N2
			1.6.3 Nitrate Leaching
		1.7 Conclusions
		References
	Chapter 2: Ecophysiology of Nitrogen in Symbiotic Relationships of Plants and Microorganisms
		2.1 Introduction
		2.2 Ecophysiology of Nitrogen in Plants
		2.3 Nitrogen and the Symbiotic Relationships of Plants and Fungi
			2.3.1 Arbuscular Mycorrhizal Fungi
			2.3.2 Ectomycorrhizal Fungi
		2.4 Nitrogen and the Symbiotic Relationships of Plants and Diazotrophic Bacteria
			2.4.1 Introducing the Rhizobia Group
			2.4.2 Establishment of the Symbiotic Plant-Rhizobia Relationship
			2.4.3 Importance of the Plant-Rhizobia Symbiosis Formation
		2.5 Final Considerations
		References
	Chapter 3: Ecological Perspectives on Soil Microbial Community Involved in Nitrogen Cycling
		3.1 Introduction
		3.2 Soil Microbiology (Historical Perspectives)
			3.2.1 Soil Microorganism Habitat
			3.2.2 Influence on Soil Microorganisms of Plants
			3.2.3 Processes of Soil Biological and Microbial Diversity
		3.3 Nitrogen Transformations
			3.3.1 Nitrogen Mineralisation and Immobilisation
		3.4 N Cycling Taxa in Soils
			3.4.1 Bacterial Nitrogen Cycling in Soils
			3.4.2 The Role of Fungi in N Cycling
			3.4.3 Viruses as Drivers of N Cycling
		3.5 N Cycling Genes in Soils
			3.5.1 Nitrification Inhibition
				3.5.1.1 Inhibition of Nitrification
			3.5.2 Denitrification
		3.6 Soil Nitrogen Transitions
		3.7 Landscape Nitrogen Movement
		3.8 Soil Biota Ecology and Its Function
			3.8.1 Mechanisms that Drive Community Structure
				3.8.1.1 Physiological Limitations to Survival
				3.8.1.2 Intraspecific Competition
				3.8.1.3 Dispersal in Space and Time
				3.8.1.4 Interspecific Competition
				3.8.1.5 Direct and Indirect Effects of Exploitation
				3.8.1.6 Mutualistic Interactions
				3.8.1.7 Community Impacts on Abiotic Factors
				3.8.1.8 Community Variation among Soil Habitats
				3.8.1.9 Community Structural Changes through Time
		3.9 Ecosystem Role Effects of the Microbial Population Organisation
			3.9.1 Energy Flow
			3.9.2 Nutrient Cycles
			3.9.3 Emergent Properties
		3.10 Evaluation of Soil Fertility by Assessing Microbiological Activity
		3.11 Ecological Consequences of Human Modifications to the Cycle of Nitrogen
		3.12 Nitrogen Derivatives and Future Environmental Effects
		3.13 Conclusion and Gaps in Current Knowledge
		References
	Chapter 4: Pedological Assessment of Soil Organic Carbon and Total Nitrogen Contents in Wetland Rice Ecosystems of Majuli Rive...
		4.1 Introduction
		4.2 Materials and Methods
			4.2.1 Study Area
			4.2.2 Rice System in Majuli
			4.2.3 Soil Data Base
			4.2.4 Laboratory Analysis
			4.2.5 Calculation of Stocks of Total Nitrogen and Organic Carbon in Soil
			4.2.6 Statistical Analysis
		4.3 Soil Organic and Total N in Relation to Soil Types and Soil Properties
			4.3.1 Depth Distribution Function of Organic Carbon (OC) and Total Nitrogen (TN)
			4.3.2 Vertical Distribution of Organic Carbon and Total N Stocks
			4.3.3 Relation of Geomorphic Units on Stocks of SOC, TN, and C/N
			4.3.4 Stratification of Clay, Organic Carbon, Total Nitrogen and Carbon to Nitrogen Ratio in Paddy Growing Soils
		4.4 Pedogenic Assessment of SOC, TN, and C/N in Paddy Soils
		4.5 Conclusion
		References
Part II: Nitrogen Cycle and Pathway
	Chapter 5: Functional Nitrogen in Rhizosphere
		5.1 Introduction
		5.2 Rhizosphere
			5.2.1 Root Exudates and Composition
			5.2.2 Rhizosphere Versus Bulk Soil
		5.3 Nitrogen
			5.3.1 Plant Available N Sources in Soil-Root Interface
			5.3.2 N cycle and Microbial Nitrogen Transformations in Rhizosphere
				5.3.2.1 Nitrogen Fixation in Rhizosphere
					Biological N Fixation
					Symbiotic N Fixation
					Nitrogenase Enzyme and Process of Nodulation
					Alternative N Fixation Systems
					Quantification of N Fixed through Non-symbiotic N Fixation
				5.3.2.2 N Mineralization
					Aminization
					Ammonification
					Nitrification
				5.3.2.3 Immobilization
				5.3.2.4 Denitrification
			5.3.3 Nitrogen Cycling in Rice
				5.3.3.1 Nitrogen Mineralization-Immobilization Reactions and its Relevance with Respect to Plant N Uptake in Rice Rhizosphere
					Environmental Perspectives of Nitrification and Denitrification in Rice Rhizosphere
				5.3.3.2 Nitrogen Fixation in Rice Soils
			5.3.4 Nitrogen Uptake in Rhizosphere
				5.3.4.1 Forms of N Uptake in the Rhizosphere
				5.3.4.2 Factors Influencing Forms of Nitrogen Uptake in the Rhizosphere
					Changes in Soil Properties as Affected by N Form Uptake
			5.3.5 Other Microbial Interactions and their Role in N Dynamics
			5.3.6 Conclusion
		References
	Chapter 6: Potential Contribution of Soil Microflora and Fauna in Nitrogen Cycle: A Comprehensive Study
		6.1 Introduction
		6.2 Soil Microflora: Potential Player in Nitrogen Cycling
			6.2.1 Bacteria
				6.2.1.1 Nitrogen Fixers
				6.2.1.2 Nitrifying Bacteria
				6.2.1.3 Anammox Bacteria
				6.2.1.4 Denitrifying Bacteria
				6.2.1.5 Archaea Bacteria
			6.2.2 Role of Fungi in Nitrogen Cycling
				6.2.2.1 Role of Arbuscular Mycorrhizal Fungi in Nitrogen Cycle
				6.2.2.2 Other Fungi
					Codenitrification
					Fermentation of Ammonia
		6.3 Role of Soil Fauna in Nitrogen Cycle
			6.3.1 Annelids
			6.3.2 Nematoda
			6.3.3 Arthropoda
		6.4 Conclusion
		References
	Chapter 7: Unravelling Microbial Nitrogen Pathway in Rhizosphere
		7.1 Introduction
		7.2 Microbial Communities in Rhizosphere
		7.3 Relation Between Plants and Microorganisms
			7.3.1 Effect of Plants on Soil Microflora
				7.3.1.1 Root Mass of Plants
				7.3.1.2 Root Excretions
				7.3.1.3 Root Residue
			7.3.2 Effect of Soil Microorganisms on Plants
				7.3.2.1 Microbial Activators
				7.3.2.2 Microbial Inhibitors
		7.4 Microbial Nitrogen Pathways
			7.4.1 Extracellular Depolymerase
				7.4.1.1 Regulation
			7.4.2 Nitrogen Mineralization
				7.4.2.1 Urease
				7.4.2.2 Amino-Acid Oxidase
		7.5 Metagenomic Analysis
			7.5.1 Metagenomic Analysis of Nitrogen Cycle
			7.5.2 Response of Nitrogen Cycle to CO2
		7.6 Conclusion
		References
	Chapter 8: Roles of Root Exudates in Different Processes in the Nitrogen Cycle in the Rhizosphere
		8.1 The Nitrogen Cycle: An Overview
		8.2 Root Exudates: Current-Status
		8.3 Root Exudates and Different Processes in the Nitrogen Cycle
			8.3.1 Root Exudates, Asymbiotic Relationships, and Nitrogen Fixation
			8.3.2 Symbiotic Nitrogen Fixation and Root Exudates
		8.4 Root Exudates Control Loss of Nitrogen Through Denitrification and the Anammox Process in the Nitrogen Cycle
		8.5 Root Exudates and the DNRA Process
		8.6 Nitrogen Mineralization and Uptake by Plant Roots
		8.7 Conclusion
		References
Part III: Techniques and Applications
	Chapter 9: Techniques for Improving Nitrogen Use Efficiency in Rice
		9.1 Introduction
		9.2 What Factors Does NUE Depend on?
			9.2.1 Application Fertilizer Types
			9.2.2 Water Irrigation Management
			9.2.3 Rice Cultivars
		9.3 Some Methods to Increase Nitrogen Use Efficiency in Rice
		9.4 Nitrogen Forms as a Particular Index
		9.5 Compounds Application and Their Effects
		9.6 Agricultural Managements
		9.7 Laboratory Analysis Types
		9.8 Environmental Issues and Problems
		9.9 Conclusion
		References
	Chapter 10: Tools for Characterization of Nitrogen Fixing Microbes
		10.1 Introduction
		10.2 Nitrogen Fixation
		10.3 Molecular Tools for Characterization of Nitrogen Fixing Microbes
			10.3.1 Molecular-Based Techniques
			10.3.2 16S rRNA Gene Based Approach
			10.3.3 Amplified Ribosomal DNA Restriction Analysis (ARDA)
			10.3.4 The nifH Gene Based Approach
			10.3.5 Denaturing Gradient Gel Electrophoresis (DGGE)
		10.4 Conventional Tools
			10.4.1 Culture Based Techniques
			10.4.2 Acetylene Reduction Assay
			10.4.3 Detecting Nitrogen Concentration Using Nitrogen Isotope
		References
	Chapter 11: Biopriming is Emerging as a Supplemental Strategy for Improving Nitrogen Use Efficiency of Crop Species
		11.1 Nitrogenous Fertilizer-Energy Intensive/Non-renewable Energy
		11.2 Nitrogen-No Alternative Source; Supplementation and Improving Rhizosphere Efficiency Only Option
		11.3 Possible Microbes as a Suitable Agent for Biopriming
		11.4 Probable Mechanism Involved
		11.5 Biopriming Mediated NUE in Different Crops
		11.6 Conclusions and Way Forward
		References
	Chapter 12: Overview of the Role of Nitrogen in Copper Pollution and Bioremediation Mediated by Plant-Microbe Interactions
		12.1 Plant Growth-Promoting Bacteria
		12.2 Copper Resistance in Bacteria
		12.3 Bioremediation of Copper and Promotion of Plant Growth
		12.4 Conclusions
		References
Part IV: Metagenomics
	Chapter 13: Metagenomics for Improving Soil Fertility
		13.1 Introduction
		13.2 Importance of Studying Soil Microbiome
		13.3 The Difficulty in Studying Soil Microorganisms
		13.4 Microbes in Soil Health and Fertility
		13.5 Emerging Technologies in Microbial Population Studies
		13.6 Metagenomics as a Means to Unlock the Unknown
		13.7 Soil Metagenome Updates
		13.8 Concluding Remarks
		References
	Chapter 14: Soil Microbial Diversity and Metagenomics
		14.1 Introduction
		14.2 Soil Microbiome
		14.3 Molecular Approaches for Measuring Soil Microbiome
		14.4 PCR-Based Approaches
		14.5 Concept of Metagenomics
			14.5.1 Metagenomic-Based Studies on Soil Microbiome
			14.5.2 Metagenomic Insight of Soil Management Practices
			14.5.3 Functional Metagenomic-Based Insight of Soil Enzymes
		14.6 Conclusion
		References
Part V: Bacteria in Nitrogen Fixation
	Chapter 15: Beneficial Effects of Nitrogen-Fixing Bacteria for Agriculture of the Future
		15.1 Introduction
		15.2 Why Nitrogen Fixation is Important to Agriculture?
		15.3 How Useful is Nitrogen-Fixing Bacteria in Agriculture
		15.4 Why Azospirillum Brasilense?
			15.4.1 Regulation of Nitrogen Fixation in A. brasilense
			15.4.2 Nitrogen-Fixing Bacteria as Biofertilizer
				15.4.2.1 Rhizobium
				15.4.2.2 Azospirillum
				15.4.2.3 Azotobacter
		15.5 Blue Green Algae (BGA) and Azolla
		15.6 Nitrogen-Fixing Endophytes
			15.6.1 Nitrogen Fixation by Free Living Heterotrophs
		15.7 Associative Nitrogen Fixation
		15.8 Symbiotic Nitrogen Fixation
		15.9 Recent Advances in Biological Nitrogen Fixation in Agricultural System
		15.10 Global Estimates of BNF
			15.10.1 Nitrogenase Biotechnology
			15.10.2 Endophytes
			15.10.3 Advances in Non-Legume BNF
			15.10.4 Heterotrophic N Fixation
			15.10.5 Endophytic N Fixation
		15.11 Advances in Legume BNF
		15.12 Climate Change and BNF
			15.12.1 Temperature Stress
			15.12.2 Drought Stress
			15.12.3 Nutrient and Metal Stress
			15.12.4 Salinity Stress
		15.13 Conclusion
		References
	Chapter 16: Functional Diversity of Nitrogen-Fixing Plant Growth-Promoting Rhizobacteria: The Story So Far
		16.1 Introduction
		16.2 Biological Nitrogen Fixation (BNF)
		16.3 Symbiotic Nitrogen Fixation Among Legumes
		16.4 Nitrogen Fixation Within Nonlegumes
			16.4.1 Rhizobacterial Nitrogen Fixation Among Some Cash Crops
			16.4.2 Rhizobacterial Nitrogen Fixation and Growth Improvement Cases
		16.5 Nitrogen-Fixing Rhizobacteria Plant Interactions
		16.6 Mechanism of Plant Growth Promotion by Nitrogen-Fixing Rhizobacteria
		16.7 Bioremediation of Pollutants Through Nitrogen-Fixing Rhizobacteria
		16.8 Mediation of Stress Tolerance in Plants Through Nitrogen-Fixing Rhizobacteria
		16.9 Climate Change and Nitrogen-Fixing Rhizobacteria
		16.10 Nitrogen-Fixing Rhizobacteria and Biofilm
		16.11 Nitrogen-Fixing Rhizobacteria and Nanoparticles
		16.12 Conclusion
		References
	Chapter 17: Bacterial Mutants for Enhanced Nitrogen Fixation
		17.1 Introduction
		17.2 Plant-Microbe Interactions in the Rhizosphere
		17.3 Biological Nitrogen Fixation
		17.4 Bacterial Strain Improvement
		17.5 Mechanism of Mutation
		17.6 Physical Mutagenesis
		17.7 Chemical Mutagenesis
		17.8 Site-Directed Mutagenesis
		17.9 Bacterial Mutation for Enhanced Nitrogen Fixation
		17.10 Conclusion
		References
	Chapter 18: Perspectives on Nitrogen-Fixing Bacillus Species
		18.1 Introduction
		18.2 Role of Bacillus Species in Nitrogen Fixation
			18.2.1 Nitrogen Metabolism in Bacillus Species
		18.3 Applications of Nitrogen-Fixing Bacillus Species
		18.4 Bacillus Species as Plant Growth Promoters
		18.5 Bacillus Species as Plant Protectors
		18.6 Conclusion
		References
	Chapter 19: Quorum Sensing Enhances Nitrogen Uptake in Plant
		19.1 Introduction
		19.2 How Bacteria Talk to each Other
			19.2.1 Synthesis and Regulator of AHL Compound
			19.2.2 AHL Reporters
			19.2.3 AHL Degradation
		19.3 The Symbiotic Bacteria Interact through Nodulation
		19.4 Role of the Plasmid in Signalling Symbiosis
		19.5 QS Signalling in Symbiotic Nitrogen Fixing Bacteria
			19.5.1 Sinorhizobium Meliloti
				19.5.1.1 sinI and sinR
				19.5.1.2 expR
				19.5.1.3 Lux-R Regulator
				19.5.1.4 traI, traR, and meII
			19.5.2 Rhizobium Leguminosarum
				19.5.2.1 cinI and cinR
				19.5.2.2 raiI and raiR
				19.5.2.3 rhiI and rhiR
				19.5.2.4 traI and traR
			19.5.3 Rhizobium Etli
				19.5.3.1 cinI and cinR
				19.5.3.2 raiI and raiR
				19.5.3.3 traI and traR
		19.6 Quorum Sensing Signalling in Free Living Diazotrophs
		19.7 Conclusion
		19.8 Future Prospective
		References
Part VI: Fungi in Nitrogen Fixation
	Chapter 20: Fungi and Nitrogen Cycle: Symbiotic Relationship, Mechanism and Significance
		20.1 Introduction
		20.2 Nitrogen Cycle and Microbes
			20.2.1 Nitrogen Fixation
			20.2.2 Nitrification
			20.2.3 Denitrification
			20.2.4 Co-Denitrification
			20.2.5 Microbes Involved in Nitrogen Cycle
		20.3 Bacteria Vs Fungi: Role in Nitrogen Cycle
		20.4 Fungi as Symbionts
		20.5 Denitrification and Co-Denitrification Mechanism
		20.6 Significance of Fungus in Nitrogen Cycle
		20.7 Conclusion
		20.8 Future Scope of Research
		References
	Chapter 21: Arbuscular Mycorrhiza in Sustainable Plant Nitrogen Nutrition: Mechanisms and Impact
		21.1 Introduction
		21.2 Arbuscular Mycorrhizal Fungi
		21.3 Uptake of N by AM Fungi
			21.3.1 Organic N Uptake
			21.3.2 Inorganic N Uptake
		21.4 Translocation of N via AM Fungi
		21.5 Role of AM Fungi in Symbiotic N2 Fixation
		21.6 Asymbiotic Soil Microorganisms in N Nutrition
		21.7 Nitrogen Uptake under Intercropping System
		21.8 Stimulation of Soil Microbial Activity by AM Fungi
		21.9 Modulation of Plant N Use Efficiency
		21.10 AM Fungi in the N Cycle
		21.11 Reduction of Nitrous Oxide (N2O) Emission
		21.12 Conclusion
		References
	Chapter 22: Nitrogen Fixing Fungi for Development of Biofertilizer and Future Strategies
		22.1 Introduction
		22.2 Biofertilizer: A Potential Approach for Sustainable Agriculture Development
			22.2.1 Biofertilizers and Their Necessity
			22.2.2 Carriers for the Preparation of Biofertilizers
			22.2.3 Classification of Biofertilizers
			22.2.4 Plant Growth Promoting Fungi (PGPF)
			22.2.5 Relationship Between Biofertilizers and Bioremediation of Metals
			22.2.6 Biofertilizers and Environmental Stress Management in Plants
		22.3 Nitrogen Fixing Biofertilizer: Mechanism and Growth Promotion
			22.3.1 Association of Bacteria with Fungi
			22.3.2 Mechanism
			22.3.3 Nitrogen Fixation and Uptake
			22.3.4 Plant Growth and Development
		22.4 Conclusion
		References
	Chapter 23: Iron Toxicity and Its Relation to Nitrogen and Phosphorus Availability in Ectomycorrhizal Fungi
		23.1 Introduction
		23.2 Iron in the Soil and in Plants
		23.3 Mechanisms of Iron Tolerance by Ectomycorrhizal Fungi
		23.4 The Relationships between Iron, Phosphorus, and Nitrogen in Ectomycorrhizal Fungi
		23.5 Conclusion and Future Prospects
		References
Part VII: Algae in Nitrogen Fixation
	Chapter 24: Role of Algae in Soil Nitrogen Fixation
		24.1 Introduction
		24.2 Non-biological Nitrogen Fixation or Physical Nitrogen Fixation
			24.2.1 Natural Nitrogen Fixation
			24.2.2 Industrial Nitrogen Fixation
		24.3 Biological Nitrogen Fixation
		24.4 Cyanophycean Algae and Nitrogen Fixation
		24.5 Heterocyst and Nitrogen Fixation
		24.6 Significance of Algal Nitrogen Fixation
		24.7 Conclusion
		References
	Chapter 25: Role of Cyanobacteria in Rhizospheric Nitrogen Fixation
		25.1 Introduction
		25.2 Diversity and Ecological Distribution of Cyanobacteria in the Plant Rhizosphere
		25.3 The Heterocyst: A Potent Diazotrophic Cyanobacterial Cell
		25.4 Role of Rhizospheric Cyanobacteria in Nitrogen Fixation
		25.5 Significance of Cyanobacteria in Nitrogen Fixation
		25.6 Metabolic Interconnections Established by Cyanobacteria in Biogeochemical Cycles Operating in the Rhizosphere
			25.6.1 Nitrogen-Fixing Cyanobacteria
			25.6.2 Nitrogen-Fixing Ecostrategists
			25.6.3 Importance of the Carbon/Nitrogen Balance
		25.7 Associative and Non-associative Nitrogen-Fixing Symbioses with Terrestrial Vegetation
			25.7.1 Associative Nitrogen Fixation: Root-Nodule Symbiosis
			25.7.2 Biological Nitrogen Fixation
			25.7.3 Nitrogen Fixation by Moss-Cyanobacterial Associations
			25.7.4 Moss-Cyanobacterial Associations in Boreal Forests
		25.8 Use of Cyanobacteria Inoculants as Important Biofertilizers in Sustainable Agriculture
			25.8.1 Uses in Organic Farming
				25.8.1.1 Crop Rotation
				25.8.1.2 Green Manure Application
				25.8.1.3 Cover Cropping
				25.8.1.4 Avoidance of Synthetic Fertilizers and Pesticides
				25.8.1.5 Planting of Habitat Corridors
			25.8.2 Multidimensional Role of Cyanobacteria in Organic Farming
		25.9 Advantages of Biofertilizers over Chemical Fertilizers
		25.10 Conclusion and Future Perspective
		References
	Chapter 26: Molecular Aspects and Oxygen Relations of Nitrogen Fixation in Cyanobacteria
		26.1 Introduction
			26.1.1 The Cyanobacteria
			26.1.2 Nitrogen Fixation
				26.1.2.1 Effects of Oxygen on Bio-Nitrogen fixation
			26.1.3 Different Strategies: Cyanobacterial Nitrogen Fixation
			26.1.4 Different Strategies for Moving to Areas with the Most Favorable Conditions
		26.2 Effect of Oxygen on Nitrogen Fixation
			26.2.1 Nitrogen with Oxygen Defense
			26.2.2 Diffusion of Controlled Oxygen
			26.2.3 Respiratory Safety Measures
			26.2.4 Hydrogenase Activity
			26.2.5 Protecting Enzymes from Reactive Oxygen Sources
		26.3 Incompatibility Photosynthesis in Cyanobacteria D Nitrogen Fixation
			26.3.1 Unique Problem in Cyanobacteria with Nitrogen Fixation
			26.3.2 Detection Step of Cyanobacteria N2-Fixing Potential
			26.3.3 N2 Fixation and Possible Oxygen Photosynthesis
		26.4 Oxygen Nitrogen Defense in Non-heterocystous Cyanobacteria
			26.4.1 Gloeothece
			26.4.2 Synechococcus
			26.4.3 Plectonema
			26.4.4 Microcoleus
			26.4.5 Oscillatoria
			26.4.6 Trichodesmium
		26.5 Nitrogenic Preservation of Oxygen in Heterocystous Systems
			26.5.1 Molecular Biology of Cyanobacterial N2 Fixation
			26.5.2 Genetic Regulation of Cyanobacterial Nitrogen Fixation
		26.6 Genetics (Cyanobacteria)
			26.6.1 16S rRNA Gene
			26.6.2 Symbiotic Cyanobacteria
			26.6.3 Stress of Oxygen and Nitrogenase Defense in Nature
		26.7 Expression of Oxygen Tension and Nif Genes in Cyanobacteria
		26.8 Evolutionary Considerations
		26.9 Conclusion and Future Perspectives
		References