Enhanced arsenic accumulation in engineered Pseudomonas putida via heterologous expression of a DNA-binding transcription repressor ArsR.

Arsenic is a highly toxic metalloid that poses significant environmental and health risks due to its widespread presence in soil, water, and industrial processes. Its accumulation in living organisms can lead to severe health issues, underscoring the need for effective bioremediation strategies. In this study, the gene encoding ArsR from Corynebacterium glutamicum (CgArsR1) was cloned into the plasmid pSEVA234 and transformed into Pseudomonas putida KT2440. Following induction with isopropyl β-d-1-thiogalactopyranoside (IPTG), the CgArsR1 protein was detected in the soluble fraction of the recombinant strain (P-CgArsR). This strain demonstrated enhanced tolerance to both arsenite (As) and arsenate (As) at higher concentrations compared to the control strain with the empty vector. The resting cells of P-CgArsR accumulated 250 μg g dry cell weight (DCW) of As and 150 μg g DCW of As, while the control cells accumulated only 100 μg g of either form. Optimal arsenic accumulation occurred at pH 7, reaching a maximum of 200 μg g DCW, while NaCl negatively affected accumulation, reducing it to 100 μg g DCW at 120 mM NaCl. These results indicate that engineered strains could effectively remediate arsenic in wastewater with NaCl concentrations between 0 and 40 mM, highlighting their potential in bioremediation efforts.