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Arsenic; Bioremediation plants; Genome sequencing

Introduction

An international environmental hazard is soil and groundwater contaminated by arsenic. Groundwater and soil contamination by arsenic is more common in deltaic alluvial regions surrounding the Ganga Bramhaputra Meghna river basin in Bangladesh and India. The majority of the arsenic found in groundwater and soil comes from geological sources. The WHO and USEPA's maximum allowable limit for arsenic in groundwater is exceeded in some areas of West Bengal, India [1-3].

Methodology

Some areas of Murshidabad, Nadia, Bardhaman, Malda, South and North 24 Pargana district in West Bengal have extremely high levels of arsenic contamination in their groundwater. There have been reports of groundwater contamination containing arsenic from 24 blocks in the Murshidabad district. The maximum amount of arsenic detected in the Murshidabad district's groundwater is 3 mg/L. Several blocks in the Murshidabad district, including Bhagobangola I, Bhagobangola II, Jalangi, and Beldanga I, exhibit concerningly elevated levels of arsenic in both soil and groundwater. There have been reports of groundwater contamination containing arsenic from every block in the Nadia district. The highest amount of arsenic found in tubewells in the Nadia district has been reported to be 3.2 mg/L.

More than 0.1 mg/L of arsenic is present in the groundwater of the Purbasthali block in the Bardhaman district. An arsenic-contaminated paddy field in Giaghata block, North 24 Pargana, has been found to contain 22.8 mg/kg of arsenic. As a result, millions of people are impacted by arsenic poisoning, and many areas of West Bengal, India, are hotspots for arsenic.

It has been possible to isolate bacteria that are resistant to arsenic from a number of hotspots in West Bengal, India. Numerous of these arsenic-tolerant bacteria demonstrated the ability to promote plant growth and perform arsenic bioremediation. For instance, from arsenic-contaminated groundwater in the Purbasthali block of Bardhaman, West Bengal, Kabiraj et al. isolated strains of Micrococcus luteus and Bacillus pacificus that were tolerant to arsenic. Micrococcus luteus isolated strain was able to withstand 390 mg/L arsenite.

Bacillus pacificus strains that are tolerant of arsenic can grow in both 10 mM arsenite and 20 mM arsenate. The genome of Bacillus pacificus contained arsenic resistance genes, such as arsC, arsB, arsR, etc. Both types of bacteria have the ability to oxidize arsenic into a less harmful form and adsorb it onto their surfaces. By generating proline, gibberellic acid, and indole acetic acid (IAA), they both accelerated the growth of rice seedlings. The minimum inhibitory concentration (MIC) of Alcaligenes faecalis subsp. phenolicus DSM 16503 T, which was isolated from the Kulik river in Raiganj, Uttar Dinajpur, West Bengal, was found to be 500 µg/ml for arsenite and 2500 µg/ml for arsenate. The same study area's Serratia marcescens NBRC 102204 T isolate revealed MIC values of 600 µg/ml and 1800 µg/ml.

Conclusion

Arsenic oxidation, adsorption, and bioaccumulation potential were demonstrated by both isolates. According to Roy, the genome of these bacteria revealed the presence of the arsR, arsB, and arsC genes, which are in charge of arsenic tolerance. In bacteria, the arsRBC, arsRABC, and arsRDABC operons contain the genes arsR, arsB, and arsC (Shamim, 2018) [4-10]. Isolated from arsenic-contaminated soil in Bhagobangola I, Murshidabad, West Bengal, Lysinibacillus sp. and Bacillus safensis demonstrated notable growth in the presence of 76.98 mM and 88.53 mM of arsenite and 560.88 mM and 721.13 mM of arsenate, respectively. Additionally, these bacteria demonstrated the ability to biotransform arsenite into the less toxic form of arsenate as well as bioaccumulate and bioadorption. Additionally, for 50 ppm of arsenic, they demonstrated more than 30% arsenic bioremediation in less than a day hypertolerant faecal arsenic.

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