Identification of nitrogen fixation bacteria by phenotypically and molecularly with PCR technique isolated from different soils

The aim of this study is to identify nitrogen-fixing bacteria isolated from different soils by phenotypic and molecular methods using PCR. Samples were collected on March 2022 from six various agricultural fields at the University of Tikrit within the root zone of some planted plants, placed in sterile plastic bags, and then the isolation and laboratory diagnosis was started. The samples of the plant are (Alfalfa, Cowpea, Bean, and Rosa davidii). All isolates were screened on the basis of their metabolic activity, then cultured in test tubes with and without L-Tryptophan on sterile GPM broth. For a week, the test tubes were covered and incubated. The results showed that the molecular characterization of the bacterial isolates based on the percentage of the 16S rRNA gene sequence matched with the bacterial strains and the species match is 99% (less than 1% difference). In the case of Aeromonas veronii, the genome can contain up to Six copies of the 16S rRNA gene, each differing by up to 1.5%. This indicates intra-genome heterogeneity of the 16S rRNA gene among aeromonads that any bacterial selections based on 16S rRNA distance scores greater than 1% are not appropriate for use in a diagnostic or public health reference laboratory. Conclusion: Bionitrogen fixation, as a sustainable source of nitrogen, has the potential to replace the requirements for industrial nitrogen production. This isolate can be used as a good candidate for the manufacture of biofertilizers, helping to restore soil fertility and crop response.