Abstract

Zinc (Zn) is an essential micronutrient to support many physiological and biochemical functions in plants, such as enzyme activation, protein synthesis, and growth regulation. But bioavailability in calcareous soils is limited, like those found in many production areas including Erbil Governorate, Iraq. Cause by high soil pH, and zinc can become tied up in indissoluble forms resulting in reduced availability to plants. To solve this problem the current study intended to isolate, characterize, and molecularly identify zinc-solubilizing bacteria (ZSB) from agricultural soils in the Erbil area. Soil samples were collected from the rhizosphere zones of different cultivated plants because the levels of microbial activity are usually greater in these locations. The bacterial isolates were screened for their Zn-solubilizing ability employing the Pikovskaya's agar medium, with zinc oxide (ZnO) as a poorly soluble form of zinc. Seventy-one (71) bacterial isolates were isolated and analyzed. Three of these isolates (Bacillus subtilis, Delftia tsuruhatensis, and Pseudoxanthomonas mexicana) had much better Zn solubilizing ability, each with a clear halo and were determined to have solubilization indices (SI) > 2.5. The bacterial isolates were identified with morphological, biochemically, and molecular analysis using 16S rRNA gene . Quantitative analysis of the strains' growth in liquid culture presented via Atomic Absorption Spectroscopy (AAS) showed solubilising large amounts of zinc. Overall, it is conceivable that the identified ZSB isolates might provide excellent tools as bio-fertilizers for increasing zinc availability in soils with zinc deficiency, leading to better plant growth and improved soil health. The use of these indigenous strains may represent an environmentally friendly and sustainable strategy for maximizing agricultural productivity in the area.