Pritam Mukherjee

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-induced global pandemic, caused by coronavirus disease 2019 (COVID-19), has taken a toll on millions of lives worldwide. Hence, there is an increasing need for accurate disease diagnosis to prevent rapid transmission and provide immediate treatment to patients having mild to severe symptoms of COVID-19 on an urgent basis. Immunoassays are among the several developed techniques for COVID-19 diagnosis. These are generally biochemical tests designed to identify the presence and level of a SARS-CoV-2-specific biomarker employing either antigens (Ags) or antibodies (Abs). Immunoassays rely on a competitive affinity reaction between the target immunological biomarker (Ag/Ab) and other (bio)molecules present in a patient’s sample for the limited binding sites on the immobilised capture molecule (Ab/Ag). Unlike conventional immunoassays, including quantitative/semi-quantitative serology tests that detect circulating anti-SARS-CoV-2 Abs using enzyme-linked immunosorbent assay (ELISA) and/or chemiluminescent immunoassay (ChLIA) techniques, rapid immunoassays, or rapid diagnostic tests (RDTs), are qualitative, simple-to-use assays that utilise an immunochromatographic (lateral flow) test format. Moreover, such tests can be conducted at or near the point of care (PoC) without requiring any high-throughput laboratory infrastructure. Based on the mechanism of detection, SARS-CoV-2 RDTs can be broadly classified into two types, namely (1) Ag tests, which directly identify the SARS-CoV-2 viral Ag(s), and (2) Ab tests that identify one or more variants of antiviral Abs secreted by the host immune system in response to viral infection. Although effective, both techniques have certain limitations. New developments in existing colourimetric lateral flow immunoassays (LFIAs) are underway to address these issues and challenges. Ag-detecting RDTs (Ag-RDTs) are expected to significantly broaden the testing domain, enabling more precise viral load estimation, cost-effective treatment for infected persons, and the formulation of adequate prophylactic measures. In contrast, serology tests [including Ab-detecting RDTs (Ab-RDTs)] could be used for serosurveillance of patients recovered from COVID-19.

Macrophytes have the potential to withstand pollutant-induced stress and can be used to clean contaminated water using phyto-extraction, phyto-degradation, phyto-filtration, phyto-stimulation, and phyto-volatilization technique(s). Phytoremediation through constructed wetlands (CWs) for eliminating inorganic and organic pollutants from household sewage and wastewater has attracted scientific attention. CWs are artificially engineered treatment systems that utilize natural cycles or processes involving soils, wetland vegetation, and plant and soil-associated microbial assemblages to remediate contaminated water and improve its quality. Herein, we present a detailed assessment of contaminant removal effectiveness in different CW systems, i.e., free-water surface or surface-flow constructed wetlands (FWSCWs/SFCWs), subsurface-flow constructed wetlands (SSFCWs), and hybrid constructed wetlands (HCWs). Several wetland floral species have been reported as potential phytoremediators, effectively reducing aquatic contamination through biodegrading, biotransforming, and bioaccumulating contaminants. Water hyacinth (Pontederia crassipes) is one of the most resistant macrophytes, capable of tolerating high nitrate (NO₃⁻) and phosphate (PO₄²⁻) concentrations. Other aquatic weeds also effectively alleviate biological oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids (TDS), and pathogen levels and ameliorate the impact of different ionic forms of nitrogen (N), phosphorus (P), and trace elements (TEs). The review primarily focuses on using hydrophyte(s)-microbe(s) associations in different CWs as an essential phytoremediation tool for sustainable management of freshwater ecosystems, ecorestoration, and prospective resource recovery, favoring a circular bioeconomy (CBE).

In recent times, East Kolkata Wetlands (EKW), a designated Ramsar site in the eastern part of megacity Kolkata, has been threatened by toxic heavy metal (HM) pollution. Besides being a natural wetland supporting biodiversity, EKW serves as a significant food basket for the city. For assessing the magnitude of HM pollution in this wetland, the three most cultivated food crops of EKW, namely Lagenaria siceraria (bottle gourd), Abelmoschus esculentus (ladies’ fingers), and Zea mays (maize), as well as the ambient soil samples, were collected during premonsoon, monsoon, and postmonsoon for 2 consecutive years (2016 and 2017). Predominant HMs like cadmium (Cd), chromium (Cr), mercury (Hg), and lead (Pb) were analyzed in the roots and edible parts of these plants, as well as in the ambient soil to evaluate the bioaccumulation factor (BF) and translocation factor (TF) of each HM in the three vegetables. It was observed that the HM content in the food crop species followed the order Z. mays > L. siceraria > A. esculentus. HMs accumulated in all three vegetables as per the order Pb > Cd > Cr > Hg. Monsoon seems to be threatening in terms of bioaccumulation and translocation of HMs as both BF and TF were highest in this season irrespective of the plant species. Hence it demands critical monitoring of HM pollution levels in this wetland and subsequent ecorestoration through distinctive plant growth-promoting rhizobacteria (PGPR)-assisted co-cultivation of these food crops with low-metal-accumulating, deep-rooted, high-biomass-yielding, and bioenergy-producing perennial grass species for minimizing HM intake.

The Halomonas species isolated from the rhizosphere of the true mangrove Avicennia marina of Indian Sundarbans showed enhanced rice growth promotion under combined stress of salt and arsenic in pot assay. Interestingly, under abiotic stress conditions, Halomonas sp. Exo1 was observed as an efficient producer of exopolysaccharide. The study revealed that salt triggered exopolysaccharide production, which in turn, increased osmotic tolerance of the strain. Again, like salt, presence of arsenic also caused increased exopolysaccharide production that in turn sequestered arsenic showing a positive feedback mechanism. To understand the role of exopolysaccharide in salt and arsenic biosorption, purified exopolysaccharide mediated salt and arsenic sequestration were studied both under in vivo and in vitro conditions and the substrate binding properties were characterized through FT-IR and SEM-EDX analyses. Finally, observation of enhanced plant growth in pot assay in the presence of the strain and pure exopolysaccharide separately, confirmed direct role of exopolysaccharide in plant growth promotion.

Fly ash (FA), the major by-product of coal-fired thermal power plants, causes significant environmental degradation owing to its injurious heavy metal contents. Leaching of arsenic (As) from ash ponds is especially significant as As released from FA can increase As concentration of drinking water above maximum contaminant level of 10 ppb. The aim of this paper was demonstration of As bioremediation potential of indigenous As resistant bacteria present in the weathered pond ash sample. Ten isolates belonging to Bacillus, Micrococcus, Kytococcus and Staphylococcus genera were characterized. Biochemical tests showed reduction of relatively non toxic arsenate to more toxic arsenite by two strains while four strains showed oxidation of arsenite to arsenate. Two exoplolysaccharide producing strains were shown to absorb As within their biomass. Total heterotrophs versus As resistant heterotrophs counting performed showed that FA was enriched with As resistant heterotrophs. Column leaching based microcosm study revealed overall As detoxification potential of the isolated microbes.

Acid mine drainage and coal fly ash both are the sibling products from man’s increasing demand for power. Mining of coal from coal mines generates acid mine drainage (AMD), and burning of coal for thermal power generation produces fly ash (FA). Although both are hazardous to the ecosystem and human health, reunion of them into one would reduce their toxic effect on nature. Mining causes exposure of hidden rock materials containing an abundance of sulphide to the atmosphere. Oxidation of the metal sulphides (pyrite, as iron sulphide) within the surrounding rock and overburden generates acidity. Subsurface mining that pumps out water to prevent flooding releases acidic water to nearby areas, known as acid mine drainage. Tailings piles, mine waste rock dumps, and coal spoils contribute in AMD. Improper disposal of the fly ash contaminates the soil, water and air by leaching of the pollutants or air borne particulate matters. However filler properties and presence of macronutrients makes fly ash an excellent filler material for mine sites, and its soil-like properties help in plant growth if provided with organic carbon and nitrogen. This chapter proposes development of a green cover into AMD site after treatment of the AMD site with FA.