Comprehensive Morphological, Biochemical, and Molecular Characterization of Azotobacter vinelandii Isolated from Tomato (Solanum lycopersicum) Soils in Iraq and Assessment of Its Nitrogen-Fixation Efficiency

Abstract

This study involved the isolation and identification of eight Azotobacter vinelandii isolates from tomato plant soils, followed by morphological, biochemical, and molecular characterization using polymerase chain reaction (PCR). The morphological and biochemical properties of the A. Vinelandii isolates were examined using conventional methods, and these characteristics were consistent with those of Azotobacter spp. Molecular analysis confirmed the identification of the isolates obtained by traditional methods. The bacterial cells were pleomorphic, Gram-negative, motile, and positive for oxidase, catalase, gelatinase, Simon’s citrate, Voges-Proskauer, methyl red, and indole tests. The isolates were capable of nitrate reduction and nitrogen fixation in nitrogen-free liquid medium (Nfb). All eight bacterial isolates exhibited varying nitrogen-fixation capacities, with isolate AZ1 demonstrating the highest efficiency among them. PCR analysis showed a 1250-bp band confirming the presence of A. Vinelandii. Sequencing results revealed 99% similarity with A. Vinelandii sequences in the genbank (NCBI) database. Phylogenetic analysis indicated that the Iraqi isolates are closely related evolutionarily to A. Vinelandii isolates from other countries, showing 99.76% similarity.