Biosynthesis of Silver Nanoparticle by Using Bacillus Subtilis Bacteria and its Biofilm Activity

Abstract

A number of soil samples were collected from the escarpment of the Euphrates River, north of the city of Basra, by digging the soil by 5 cm, taking a portion of the soil, storing it in a sterile plastic cup, and transporting it to the laboratory. The samples were diluted with distilled water and grown on nutrient agar medium. They were purified. Bacterial isolates were obtained by taking single isolates and cultivating them on the nutrient medium using a planning method. The process was repeated until single colonies were obtained. The bacterial isolate was identified as Bacillus subtilis by diagnosing it phenotypically, examining it under a microscope, and performing biochemical tests, in addition to using a technique. PCR using the 16SrRNA gene. The supernatant solution was treated with B. subtilis bacteria With a solution of silver nitrate at a concentration of 1 mM, the color variation of the reaction mixture occurred, which was considered preliminary evidence of the formation of silver nanoparticles. The AgNPs were characterized by examination with a UV-visible spectroscopy device, and an FTIR device was used to detect the presence of active groups that contributed to the stability of the AgNPs. An SEM and TEM device were used, and the examination results showed the surface nature and the dominant spherical shape, in addition to the size, at a rate of 25 nm. An XRD device was used, and the test results showed that the AgNPs had a crystalline form. An EDX device was used, and the results revealed the presence of peaks indicating silver. The ability of AgNPs to inhibit the growth of pathogenic bacteria represented by Pseudomonas aeruginosa, E. coli, and Klebsiella. pneumonia and Staphylococcus aureus Using the etch diffusion method, the results showed that the AgNPs had a high ability to inhibit bacterial growth. A test was conducted to detect some virulence factors, such as catalase, and the effectiveness of silver nanoparticles in inhibiting them. The biofilm was detected by a microtiter plate, and the results showed the ability of the AgNPs to inhibit biofilm effectively.