This self-contained volume covers fundamental and applied aspects of nitrogen-fixation research. The book describes milestones in the discovery of the associative and endophytic nitrogen-fixing bacteria found involved with cereal crops, forage grasses, and sugar cane. It provides a comprehensive overview of their phylogeny, physiology, and genetics as well as of the biology of their association with their host plants, including tools for in situ localization and population-dynamics analysis. Also included are chapters describing the functions required for a bacterium to be competent and competitive in the rhizosphere, and analysis of associations of cyanobacteria with fungi, diatoms, bryophytes, cycads, Azolla, and Gunnera.

Zusammenfassung
Associative and Endophytic Nitrogen-fixing Bacteria and Cyanobacterial Associations This book is part of the seven-volume series that was launched a few years ago with the ambitious objectives of reviewing the field of nitrogen fixation from its earliest beginnings through the millennium change and of consolidating the relevant information - from fundamental to agricultural and environmental aspects all in one place. Volume 5 covers the biology of bacteria that associate with n- leguminous plants. The subject matter includes a wide range of associations; it covers the bacterial species that associate either with the surface or within the tissues of grasses (often referred as plant growth-promoting rhizobacteria) and also the symbiotic associations that cyanobacteria form with fungi, algae, and both lower and higher plants. This volume does not deal with the Frankia-actinorhizal plant associations, which is the topic of Volume 6. The book is divided in 13 chapters, each of which is the work of well-known scientists in the field. Just like in the other volumes of this series, the first chapter is th an historical perspective. It describes how, as early as the end of the 19 century, it was shown that plant exudation favoured the proliferation of soil bacteria in the rhizosphere, and how the first nitrogen-fixing bacteria, including cyanobacteria were isolated. The chapter covers the landmarks and scientific concepts that arose from more than one century of research in this area.

Inhalt

Preface to the Series. Preface. List of Contributors. Dedication.

1. Historical Perspective: From Bacterization to Endophytes; C. Elmerich
1. The Nitrogen Cycle: Heritage from the 19th Century

2. Nutritional Interactions between Bacteria and Plants
3. Associative Nitrogen-fixing Bacteria
4. Discovery of Nitrogen-fixing Endophytes
5. Cyanobacterial Associations

6. Concluding Remarks
   Acknowledgement
   References

   2. Molecular Phylogeny and Ecology of Root-Associated Diazotrophic a- and ß-Protobacteria;
   M. Schmid and A. Hartmann

7. Introduction
8. Tools for Molecular Phylogeny and in situ Localizationof Bacterial Isolates and Communities
9. Molecular Phylogeny and Ecology of Azospirillum and Other Nitrogen-fixing a-Subclass Protobacteria
10. Molecular Phylogeny and Ecology of Herbaspirillum, Diazotrophic Burkholderia spp., and Other Nitrogen-fixing ß-Protobacteria

11. Conclusions and Prospects for Future Studies
    Acknowledgements
    References

    3. Regulation of Nitrogen Fixation and Ammonium Assimilation in Associative and Endophytic Nitrogen-fixing Bacteria;
    F. O. Pedrosa and C. Elmerich
    1. Introduction

12. Rhizospheric and Endophytic Bacteria: General Features
13. Structural Organization of nif Genes
14. Identification of RpoN and Its Involvement in Nitrogen Fixation
15. Thr Ntr System and Control of Nitrogen Metabolism and Nitrogen Fixation
16. Regulation of Nitrogen Fixation

17. Conclusions
    Acknowledgements
    References

    4. Chemotaxis in Soil Diazotrophs: Survival and Adaptive Response;
    G. Alexandre and I. B. Zhulin
    1. Introduction

18. Gene-Expression Regulation and Chemotaxis as Adaptive Responses to Environmental changes
19. Molecular Mechanism of the Chemotactic Response: Learning from Escherichia coli

20. Directed Motility in Soil Diazotrophs
    5.Future Studies
    References

    5. Molecular Genetics of Rhizosphere and Plant-Root Colonization;
    E. Vanbleu and J. Vanderleyden

21. Introduction
22. Motility of Associative Diazotrophs
23. Attachment to Plant Roots
24. Rhizosphere Competence

25. Conclusions
    Acknowledgement
    References

    6. Microbial Production of Plant Hormones;
    B. E. Baca and C. Elmerich

26. Discovery of Phytohormones
27. Production and Role of Phytohormones
28. Pathways for Plant Hormone Biosynthesis: Common Routes in Plants, Bacteria and Fungi
29. Major Routes for IAA synthesis in Pathogenic and Beneficial Nitrogen-fixing Bacteria Associated with Plants
30. Multiple Routes for IAA Synthesis in Azospirillum
31. Other Phytohormones Produced by Plant Pathogenic and Nitrogen-fixing Associated and Endophytic Bacteria
32. Plant Growth Promotion (PGP): Role of Bacterial Phytohormone Production, ACC-Deaminase, and the Use of Synthetic Auxins

33. Concluding Remarks
    Acknowledgement
    References

    7. The Plant Growth-Promoting Effect and Plant Responses;
    S. Dobbelaere and Y. Okon
    1. N2 Fixation vs. "Hormonal" Effects: Historical Perspectives

34. Effects of Azospirillum and Other Diazotrophs on Root Morphology
35. Effects on Root Function
36. Effects on Plant Growth

37. Future Studies
    References

    8. Biocontrol of Plant Diseases by Associative and Endophytic Nitrogen-fixing Bacteria;
    R. Bally and C. Elmerich

38. Beneficial Plant-Associated Nitrogen-fixing Bacteria and Biocontrol of Plant Disease
39. Interactions within Microbial Communities: Competition
40. Biological Control against Soil-Borne Diseases
41. Regulation of Biocontrol Properties and Cell-Cell
42. Plant Response to Pathogens and Biological Control in the Rhizosphere
43. Concluding Remarks
    Acknowledgements
    References
    9. Endophytic Associations of Azoarcus spp;
    B. Reinhold-Hurek and T. Hurek
    1. Introduction
44. The Rise of Interest in Diazotrophic Endophytes
45. Azoarcus spp. and related Genera: Strictly Plant-Associated vs. Soil Bacteria
46. Habitats and Ecophysiology
47. Interac...