Deciphering the Bioremediation Potential and PGP Signaling of a Soil-Derived Isolate Pantoea dispersa MS 3: from Spectroscopic Characterization to Phytotoxicity Assessment

Abstract

Textile industry effluent containing synthetic azo dyes pose a severe threat to environmental and soil health due to their recalcitrant and toxic nature, leading to the inhibition of aquatic photosynthesis, depletion of dissolved oxygen, reduction of soil fertility, and the formation of toxic, carcinogenic aromatic amines that bioaccumulate through the food chain. This study aimed to isolate and characterize a multifunctional bacterial strain capable of both azo dye degradation and plant growth promotion (PGP). From fifteen soil isolates, the strain MS 3 was selected for its superior performance and identified as Pantoea dispersa MS 3 (GenBank-OP303250). Quantitative assays demonstrated that MS 3 showed significant decolorization efficiencies for three structurally diverse dyes namely, Dk. Red RB (90.5%), Blue GSL (89.6%), and a peak efficiency of 92.07% for Scarlet RR. Analytical evaluation using UV-Vis, TLC, and FTIR confirmed the successful cleavage of the azo bond (-N=N-) and the biotransformation of the parent dyes into simpler intermediate metabolites. Furthermore, P. dispersa MS 3 exhibited robust PGP attributes, including N₂ fixation, phosphate solubilization (20.26 µg/mL), and the production of IAA (44.74 µg/mL), siderophore (68.6% SU), and GA3 (111.17 µg/mL). Phytotoxicity study using Vigna radiata L. revealed that bacterial treatment significantly mitigated dye-induced stress, improving germination rates from 40% in dye-polluted controls to 73.3% in treated samples, alongside enhanced seedling vigor. These results suggest that P. dispersa MS 3 is a highly effective, eco-friendly bioinoculant for the bioremediation of textile-contaminated soils and the restoration of agricultural productivity. Interestingly, the current study is the first report describing the isolation of P. dispersa MS 3 from dye-contaminated sites showing dual capability of azo dye degradation and plant growth-promoting potential.