Isolation and molecular identification for the first time in Iraq of sulfur-oxidizing bacteria and testing their possession of the plant growth stimulating criteria

To prepare environmentally friendly bio-fertilizer that enhances the properties of alkaline soils, particularly Gypsipherous soils, and promotes plant growth from pure and molecularly characterized sulfur-oxidizing bacterial isolates, 53 samples were collected on 10/February / 2022 from various agricultural sources and sites, all of the samples were inoculated in a liquid thiosulfate medium. The isolates were then streaked on solid thiosulfate medium and characterized phenotypically based on their Cutural, microscopic, and biochemical properties. Phenotypical characterization results revealed that 8 isolates exhibited the characteristics of Thiobacillus bacteria, They were given the codes B1, B2, B3, B4, B5, B6, B7, B8, and the color of the colonies was between white, creamy to yellow, Convex and smooth Negative to Gram stain, 4 isolates were motile and 4 were non-motile, 4 isolates were fast-growing they include : B1, B2, B3, B4, like that 4 isolates were slow-growing: B5, B6, B7, B8, all isolates were positive for catalase and oxidase tests. The results showed that all isolates were efficient in: Lowering the pH of the medium after 21 days of incubation, phosphate Solubilizing, Producing indole acetic acid (IAA), sulfates, as isolate B3 outperformed all isolates in these properties and recorded 4.52, 91.904 mg P l-1, 21.2 µg ml-1, 1.754% respectively and gave a heavy growth on chelating compounds medium, isolate B7 gave the lowest values, recording 7.06, 35.101 mg P L-1, 11.9 µg mL-1, and 0.884 and gave a weak growth on chelating compounds medium, Isolates that demonstrated efficient growth and possessed the criteria for promoting plant growth molecular diagnostic result for the four isolates :B1,B2,B3and B4 isolates based on the amplification of the 16S rRNA gene. The nucleotide sequences were then analyzed and compared to those of global strains listed on the (NCBI) website. The results showed that isolates B1, B2, B3, and B4 had 99.26%, 99.26%, 99.23%, and 99.17% similarity to Thiobacillus thioparus strain Starkey, Thiobacillus denitrificans strain DSM 739, Thiobacillus denitrificans strain NCIMB 9548, and Thiobacillus thiophilus strain D24TN, respectively. The isolates were assigned the accession numbers ON844981, ON844984, ON844983, and ON844982, respectively, in the National Center for Biotechnology Information (NCBI) data base. This molecular diagnosis and registration in the NCBI is the first in Iraq.