The soil and groundwater of the Bhagobangola I block of Murshidabad district, West Bengal, India is severely arsenic-contaminated. A bacterium was isolated from the garden soil of the Mahishasthali village, which could tolerate 36.49 mM arsenic (III), 280.44 mM arsenic (V) and 63 mM chromium (III), which makes it arsenic (III and V) and chromium (III) hyper-tolerant bacterium. The growth pattern of this bacterium does not show much alteration in the presence of 10 mM arsenic (III) and chromium (III), emphasizing its resistance to these heavy metals. Scanning electron microscopic analysis depicted this bacterium to be rod-shaped with a size of ~1.45 µm. 16S rDNA sequencing, followed by subsequent phylogenetic analysis, established the identity of this bacterium as Microbacterium paraoxydans. This bacterium is capable of bioremediation of arsenic and showed 30.8% and 35.2% of bioremediation for 1mM and 22.6%, and 30.5% of bioremediation for 4mM arsenite, over a period of 24 and 48 h, respectively. Microbacterium paraoxydans also exhibits potential plant growth-promoting properties such as nitrogen fixation, phosphate solubilization, indole-3-acetic acid production and production of siderophores. Therefore, the heavy metal resistance, bioremediation potential and plant growth-promoting potential of the bacterium could be utilized not only for reduction in arsenic toxicity in soil and groundwater but also for plant growth promotion.

The study addresses depth dependent arsenic, and microbial (coliform) contamination of groundwater in the shallow aquifers of Chakdah block of the Bengal Delta Plain, an issue of undeniable public health significance. Groundwater samples were collected from six gram panchayats in the Chakdah block, Nadia district, India to estimate the dissolved ions, total and fecal coliform. The risk associated with groundwater use pattern from six sites was analyzed by the sanitary risk score and the fecal coliform score. Dissolved arsenic levels in the groundwater ranges from 0.069 to 0.178 mgL⁻¹ (Mean: 0.119 mgL⁻¹). The primary anion detected was HCO₃⁻ (Mean: 222 mgL⁻¹), followed by Cl⁻ (Mean: 21 mgL⁻¹), SO₄²⁻ (Mean: 8.96 mgL⁻¹) and PO₄³⁻ (Mean: 2.26 mgL⁻¹). Chloride varies significantly (up to 147 mgL⁻¹), indicating local anthropogenic sources of pollution. Groundwater sources near surface water bodies (~ 2–3 m) have high total and fecal coliform count. Coliform count varies seasonally in groundwater and shows higher count during post-monsoon season. The fecal coliform count at all sites ranged from 10 to 100/100 mL of groundwater. According to sanitary risk analysis, the monitored tube wells could be categorized as very high risk-25.0%, high risk-58.3%, intermediate risk-11.1%, and low risk-5%. The occurrence of arsenic contamination corresponds with high coliform count, particularly in the tube wells of high risk areas. The study advocates that arsenic and microbial contamination of groundwater in the aforementioned region is a serious public health issue which needs attention (policy) at local and global platforms.