Evaluation of arsenic-Tolerant plant growth-promoting rhizobacteria from Manipur for mitigating arsenic translocation and enhancing growth in rice (Oryza sativa)

Abstract

Arsenic (As) contamination in paddy fields poses a serious risk to food safety by promoting arsenic accumulation in rice. This study evaluates the bioremediation potential of two arsenic-tolerant plant growth-promoting rhizobacteria (PGPR)—Bacillus paramycoides TNCB-27 and Pseudomonas shirazica TNB-16—isolated from agricultural soils in Thoubal, Manipur, India. Greenhouse experiments were conducted to assess their effects on arsenic uptake, translocation, and rice plant growth under arsenite [As(III)]- and arsenate [As(V)]- spiked conditions. Inoculated plants showed significantly reduced arsenic levels in shoots, likely due to enhanced root sequestration and microbial transformation of arsenic, as indicated by lower translocation factors. Morphological alterations in bacterial cells post-arsenic exposure were observed via scanning and transmission electron microscopy (SEM, TEM). Fourier transform infrared spectroscopy (FTIR) revealed changes in bacterial functional groups and exopolysaccharides, suggesting their role in arsenic binding. This is the first report on PGPR from Manipur demonstrating both arsenic remediation and plant growth-promoting abilities, offering a sustainable microbial approach to reduce arsenic bioavailability and accumulation in rice agroecosystems.