Detailed genomic and biochemical characterization and plant growth promoting properties of an arsenic-tolerant isolate of Bacillus pacificus from contaminated groundwater of West Bengal, India

Abstract

In this study, arsenic tolerating bacteria Bacillus pacificus (AKS1a) was isolated from arsenic contaminated groundwater of Purbasthali, Purba Bardhaman, West Bengal, India and its bioremediation potential was preliminary screened. This multimetal resistant strain was able to grow against more than 20 mM arsenate and 10 mM arsenite salts. The genome was more than 5.16 Mb in length, with an average of around 35.2% GC content, bearing 5403 protein coding genes. Arsenic resistant genes like arsC, arsB, arsR, etc. were also identified. Rapid Annotation using Subsystem Technology (RAST) identified 328 subsystems within the genome. Presence of six Genomic Islands (GIs) and five phage virus genomic parts indicated its ecological adaptations to overcome environmental stresses. The production of about 415 μg mL−1 indole acetic acid (IAA), 258.0 μg mL−1 gibberellic acid (GA), and 183 μg mL−1 proline by the bacterium, along with nitrogen fixation ability under in-vitro conditions, indicate its plant growth promoting potential. This was further confirmed through rice seedling growth enhancement under arsenic stress. Beside arsenite oxidation to arsenate, its arsenic adsorption property was confirmed through X-ray Fluorescence spectroscopy (XRF), Fourier Transform Infrared spectroscopy (FTIR), and Energy Dispersive X-ray spectroscopic (EDS) analysis. Genomic comparisons among 25 different strains of B. pacificus showed that there are tremendous genetic differences in respect to their accessory genome content. In future, this strain can be applied as biofertilizer or biostimulant for improving rice plant growth.