TABLE OF CONTENTS
Title page
Certification – – – – – – – –
Dedication – – – – – – – –
Acknowledgements- – – – – – –
Table of content- – – – – – – –
Chapter One
1.1 Introduction- – – – – – – –
1.2 Diazotrophs- – – – – – – –
Chapter Two
2.1 Backterial exhibiting the Diazotrophicproperty –
2.2 Mechanism and Adaptation of Diazotrophs –
2.3 Impact of the Diazotrophs on plan Growth, Health and Desease
2.4 The good effect- – – – – – –
2.4.1 Effect on nutrient Acquisition by Plant
2.4.2 Supporting plant Growth under Biotic stress
2.5 The bad effect
2.5.1 Fungi and oomycetes
2.5.2 Nematodes
2.6 The ugly side effect
2.6.1 As opportunistic hyman pathugens in the Rhizosphere.
2.6.2 Plant colonization by human pathugens
2.7 soil health status and occurrence of potential human pathogens – – – –
Chapter Three
3.0 Evidence that Diazotrophs diversity impacts N-in fult fixation rate
3.1 N fixation
3.2 Carbon fixation
3.3 N Release
3.4 C Release
3.5 Tropic interactions
3.5.1 Bacteria
3.5.2 Phytoplankton
3.53 3ooplankton and high tropic levels
3.6 Implication
Chapter Four
4.0 Summary and Conclusion
4.1 Summaries
4.2 Conclusions
Reference
CHAPTER ONE
- Introductions
Biological Nitrogen (N) fixation is the major natural process through which atmospheric dinitrogen (N2)is converted into forms that can be used by plants and animals, contributing 100-290 TgN per year to the biosphere Cleveland et al., 1999. Although the majority of Nitrogen (N) fixation in terrestrial ecosystems is carried out by symbiotic bacteria in association with plants, free-living diazotrophs in soils have been shown to be important contributors to the Nirogen (N) budgets of a number of ecosystems (shi-fang and Daniel 2008). Progress in understanding the ecological significance of free-living diazotrophs has been limited, however, by the fact that many of these organisms are recalcitrant to laboratory cultivation. The nifH gene, which encodes a subunit of the nitrogenase enzyme, Provides a useful market that can be used to study the distribution  and diversity of diazotrophs without the need for cultivation (Buckley et al., 2007).
