Delineation of Soil Arsenic and Observe Arsenic Tolerance Limit of Bacteria Isolated from Nadia, West Bengal

Arsenic, a carcinogenic metalloid polluting terrestrial and aquatic ecosystem throughout the Globe. Not only human or animals, microbes like bacteria or fungi also affected by arsenic toxicity and in high arsenic (As) contaminated pockets, crop productivity decreases due to restricted proliferation of beneficial microbes.

To fulfil the objectives of present study, soil samples were collected from four different arsenic affected blocks of Nadia district in the November 2020, which are analysed for arsenic content and bacterial count apart from physicochemical or nutrient status in Directorate of Research, Bidhan Chandra Krishi Viswavidyalaya (BCKV) Kalyani, WB.

Results revealed that plant available (3.28 mg kg^-1) and total arsenic content (16.46 mg kg^-1) was highest at Chakda block with a positive significant corelation (r=0.88) between plant available and total arsenic. Available arsenic showed a negative regression curve with bacterial colony forming unit (cfu), which was polynomial in nature. Tolerance limit of bacteria was observed by adding As₂O₃ salt in bacterial broth in varied amount (100-5000 ppm), where bacteria showed a decreasing population with increasing As content in both cfu count and optical density (OD) test with a R² value 0.92. Experiment results specify that bacteria isolated from highly As contaminated soil showed more resistance to As toxicity, might be due to exclusion or natural selection mechanism, while bacteria isolated from less contaminated soil died due to enzymatic disruption and genotoxicity.