Rhizosphere Microbiome Modulators: Contributions of Nitrogen Fixing

9 Rhizosphere microbiomes which have been implicated to enhance plant growth and yield are 10 modulated or influenced by a couple of environmental factors such as soil type, plant cultivar, 11 climate change and anthropogenic activities. In particular, anthropogenic activity such as the use 12 of nitrogen-based chemical fertilizers is associated with environmental destruction and this call 13 for a more ecofriendly strategy to increase nitrogen level of agricultural land. This feat is 14 attainable by harnessing nitrogen-fixing endophytic and free-living rhizobacteria. Rhizobium, 15 Pseudomonas, Azospirillum and Bacillus have been found to have positive impacts on crops by 16 enhancing both above and belowground biomass and could therefore play positive roles in 17 achieving sustainable agriculture. Thus, it is needful to study these rhizosphere microbiomes 18 with more sophisticated culture-independent technologies such as next generation sequencing 19 (NGS) with the prospect of discovering novel bacteria with plant growth promoting traits. This 20 review is therefore aimed at discussing factors that can modulate rhizosphere microbiomes with 21 focus on the contributions of nitrogen fixing bacteria towards sustainable agricultural 22 development and the techniques that can be used for their study. 23 24