Screening, molecular identification, and evaluation of the nutrient mobilization potential of Fluoride Resistant Bacterial isolates from fluoride-rich rice field: A case from West Bengal, India

Fluoride (F⁻) toxicity has become a significant environmental and public health concern globally. Microbial defluoridation offers a promising approach to restoring soil health, increasing crop yields, and minimizing fluoride bioaccumulation in the food chain. In the present experiment, seven bacteria with varied levels of fluoride resistance were screened out in vitro using tryptone soya agar medium supplemented with different grades of Sodium Fluoride (NaF) from the composite topsoil (0–0.2 m depth) of fluoride-rich rice fields of three blocks (Arsha, Jhalda-I, and Joypur) of the Purulia district, West Bengal, India. Using NCBI- BLAST and 16S rDNA barcode sequence-based molecular phylogeny, the seven isolates were identified as Aeromonas aquatica strain KPNA_FR1 (GenBank Acc. PP957426), Bacillus pumilus strain KPNA_FR2 (GenBank Acc. PP948725), Enterobacter sp. Strain KPNA_FR3 (GenBank Acc. PP948726), Enterobacter ludwigii strain KPNA_FR4 (GenBank Acc. PP948727), Priestia aryabhattai strain KPNA_FR5 (GenBank Acc. PP948728) Enterobacter sp. strain KPNA_FR6 (GenBank Acc. PP948729), Bacillus pumilus strain and KPNA_FR7 (GenBank Acc. PP948730). Out of these seven isolates, the most Fluoride tolerant bacterium Enterobacter ludwigii strain KPNA_FR4 can tolerate a maximum of 11,250 ppm NaF in vitro and exhibited ~ 78% defluoridation capacity from medium. The plant growth-promoting efficiency of KPNA_FR4 including other isolates concerning the solubilzation of phosphate (123.67 ± 13.41 ppm), potassium (2.49 ± 0.10 ppm) and zinc (50.80 ± 5.38 ppm) have also been reported. Thus, the isolated fluoride-resistant bacteria, having significant potential as fluoride bioremediator and biofertilizers, may be used to mitigate soil fluoride toxicity sustainably and to increase agricultural productivity as well.