Bacterial Diversity in Oil Field Environments and Evaluation of Their Ability to Biosynthesize Silver Nanoparticles (AgNPs)

Bacteria isolated from oil reservoir environments possess unique enzymes that allow them to adapt to extreme environments, making them ideal candidates for producing high-value nanomaterials that can be used in various fields. In the present study, eight samples were collected from Badra and Ahdab oil fields in Iraq, the bacteria isolated and identified based on the 16SrRNA gene, and the isolates were screened for the synthesis of silver nanoparticles (AgNPs). The characteristics of the AgNPs were analyzed using UV-Vis spectroscopy, FTIR, XRD, FE-SEM, zeta potential measurements, and dynamic light scattering (DLS). The results indicated the dominance of Gram-positive bacteria, with a percentage of 18 (72%). Genetic identification revealed that the bacteria were under 6 genera and 16 species; these genera include Enterococcus, Priestia, Enterobacter, Acinetobacter, Flavobacterium, and Bacillus. Seven new strains have been deposited in GenBank. The results of screening isolates for synthesized AgNPs showed high efficiency of a novel strain, Bacillus halotolerans strain AhWM4, with the maximum absorption peak at 430 nm. The average size of AgNPs using XRD, FE-SEM, and TEM was (31.3, 27.0, and 42.1) nm, respectively. Dynamic light scattering (DLS) measurements showed a wide dispersion with an effective diameter of 57.1 nm; the X-ray diffraction (XRD) spectrum matched the crystalline nature of the AgNPs. It also showed high stability, with a zeta potential of -42.3 mV. AgNPs have attracted considerable attention due to their staggering potential for a wide range of commercial and environmental applications.