Azotobacter biodiversity in Egypt using microbiological, biochemical, and molecular-biology multidisciplinary approach.

Abstract

The presence of Azotobacter bacteria in the soil plays an important role in increasing its fertility and enhancing plant health. Azotobacter diversity depends on several environmental factors, particularly soil texture, pH, and nutrient content. The current study investigated the diversity of Azotobacter in various soil samples collected from 10 different governorates along the river Nile valley and its delta, Northern Mediterranean shore, Sinai, and Upper Egypt regions. The sampling sites spanned different environmental and ecological conditions of the Egyptian land either cultivated (agricultural land) or uncultivated (desert land). Fifty Azotobacter isolates were isolated and characterized based on cell morphology, culture properties, physiological, biochemical, and molecular characteristics. In addition, the alginate production capacity of the isolates was investigated. The results indicated that Egyptian soils are rich in Azotobacter diversity. The isolates were Gram-negative short rods, appearing either as single cells or in diploid structures. The isolates showed high variability in alginate production where two isolates (BH3 and AST4) were the highest alginate producers (3.12 and 4.22 g alginate L^- 1), respectively. 16S-rDNA sequencing and 16S-rDNA RFLP analyses indicated that despite the presence of Azotobacter salinestris and Azotobacter vinelandii in the Egyptian soil, Azotobacter chroococcum was the predominant species. In addition, sequence analysis of the gene coding for the transcription factor AlgU confirmed the results of 16S-rRNA gene sequence analysis. RAPD-REP and BOX-PCR were used to study the polymorphism among the isolates. High levels of microbial diversity were found using these DNA primers as 6-9 fingerprinting profiles were retrieved.