Divulging diazotrophic bacterial community structure in Kuwait desert ecosystems and their N2-fixation potential

Abstract

AbstractKuwait is a semi-arid region with harsh climatic conditions with poor available soil nutrient essential for the growth of plants. Kuwait’s ecosystem is relatively N-poor ecosystem when compared to the other ecosystems. Biological nitrogen fixation (BNF) is a spontaneous process in which diazotrophic bacteria fixes the atmospheric nitrogen directly in to the bionetwork. At present, there is limited information on free-living and root associated nitrogen-fixing bacteria, their potential to fix nitrogen to aid natural plant communities in the desert of Kuwait. In this study, free-living N2-fixing bacteria were enriched and isolated from the rhizospheric soil of three keystone native plant species of Kuwait; such asRhanterium epapposum, Farsetia aegyptia, andHaloxylon salicornicum. Root associated bacteria were directly isolated from the root nodules ofVachellia pachyceras. In this study, a number of free-living and root associated dizotrophs were isolated from various rhizospheric soils of three native shrubs and root nodules from one tree species. The screened isolates were assessed for nitrogen-fixing ability and identified using Acetylene Reduction Assay (ARA) and 16s rRNA gene sequencing, respectively. Our study successfully identified all the 50 nitrogen-fixers isolated initially and out of that, 78% were confirmed as nitrogen-fixers using ARA. Among the identified nitrogen fixers, the genusRhizobiumis dominant in rhizospheric soil ofRhanterium epapposum, whereasPseudomonasandRhizobiumare dominant in the rhizospheric soil ofFarsetia aegyptia, andHaloxylon salicornicumrespectively. The speciesAgrobacterium tumefaciensis found dominant in the root nodules ofV. pachyceras. The current results indicate that plant species and their rhizospheric effects are important drivers for specificity of microbial diversity in arid soils. To our knowledge, this study is the first investigation of culture-based isolation, molecular identification, and evaluation of N2-fixing ability of diazotrophs from Kuwait desert environment.