Exploring the Genetic, Structural, and Computational Insights of Resistance Proteins in Arsenic-Bioremediation Enterobacter Strain

Abstract

Arsenic (As) tops the Agency for Toxic Substances and Disease Registry (ATSDR)'s list of toxic substances, making it a leading cause of severe heavy metal poisoning. This study examined thirty bacterial isolates for arsenic resistance, identifying sixteen strains that could tolerate up to 11,500 ppm of arsenic, a level significantly higher than previously reported. Genetic analysis using rep-PCR profiling revealed significant diversity among these resistant strains. Nine isolates with the highest arsenic tolerance were selected for further study, focusing on arsenic biosorption. Among these, Enterobacter cloacae subsp. cloacae strain FACU 1 (Ars 9) demonstrated the highest biosorption capacity, removing 85.5% of arsenic from solution, equivalent to 1415 mg/g of biomass. Molecular identification and transmission electron microscopy (TEM) confirmed the existence of arsenic on the cell surface of Ars 9. Furthermore, it was verified that this strain possessed the arsenic resistance genes Acr3(1), Acr3(2), ArsB and ArsC. These proteins' homology models were produced utilizing SWISS-MODEL and AlphaFold2, and molecular docking was applied to assess their binding affinities for arsenate (AsO4) and arsenite (AsO3). Results indicated that ArsC exhibited a higher affinity for AsO4, suggesting its role in AsO4 reduction. Transport proteins ArsB and Acr3 showed moderate affinities for AsO3, facilitating its efficient efflux. These findings offer valuable insights into bacterial arsenic detoxification mechanisms and highlight the potential of arsenic-resistant strains for bioremediation applications.