Speciation-specific chromium bioaccumulation and detoxification in fish using hydrogel microencapsulated biogenic nanosilver and zeolite synergizing with biomarkers.

Grass carp intestinal waste-mediated biosynthesized nanosilver (AgNPs) was valorized using guaran and zeolite matrices, resulting in AgNPs-guaran, AgNPs-zeolite, and AgNPs-guaran -zeolite composites. The valorized products were examined using Environmental Scanning Electron Microscopy, Energy Dispersive X-ray analysis and X-ray Diffraction analysis to confirm uniform dispersion and entrapment of AgNPs within the matrixes. These valorized products were evaluated for their efficacy in detoxifying the ubiquitous and toxic hexavalent chromium (Cr6+) in aquatic environments, with Anabas testudineus exposed to 2 mg l-1 of Cr6+ for 60 days. Remarkable reduction of Cr6+ concentration to 0.86 ± 0.007 mg l-1 was achieved with AgNPs-guaran-zeolite composite, indicating successful reclamation of contaminated water and food safety assurance. Consistency in results was further corroborated by minimal stress-related alterations in fish physiological parameters and integrated biomarker response within the experimental group treated with the AgNPs-guaran-zeolite composite. Despite observed chromium accumulation in fish tissues, evidence of physiological stability was apparent, potentially attributable to trivalent chromium accumulation, serving as an essential nutrient for the fish. Additionally, the challenge study involving Anabas testudineus exposed to Aeromonas hydrophila exhibited the lowest cumulative mortality (11.11%) and highest survival rate (87.5%) within the same experimental group. The current study presents a novel approach encompassing the valorization of AgNPs for Cr6+ detoxification under neutral to alkaline pH conditions, offering a comprehensive framework for environmental remediation.

Toxicity assessment of poultry-waste biosynthesized nanosilver in Anabas testudineus (Bloch, 1792) for responsible and sustainable aquaculture development-A multi-biomarker approach.

The current study investigates the potential utilization of poultry intestines for the synthesis of stable silver nanoparticles (AgNPs) and their impact on fish physiology. The AgNPs were synthesized and characterized using various analytical techniques. The toxicity of AgNPs on Anabas testudineus was evaluated, determining a 96-h LC50 value of 25.46 mg l-1. Subsequently, fish were exposed to concentrations corresponding to 1/10th, 1/25th, 1/50th, and 1/100th of the estimated LC50 for a duration of 60 days in a sub-acute study. A comprehensive range of biomarkers, including haematological, serum, oxidative stress, and metabolizing markers, were analyzed to assess the physiological responses of the fish. Additionally, histopathological examinations were conducted, and the accumulation of silver in biomarker organs was measured. The results indicate that silver tends to bioaccumulate in all biomarker organs in a dose- and time-dependent manner, except for the muscle tissue, where accumulation initially increased and subsequently decreased, demonstrating the fish's inherent ability for natural attenuation. Analysis of physiological data and integrated biomarker responses reveal that concentrations of 1/10th, 1/25th, and 1/50th of the LC50 can induce stress in the fish, while exposure to 1/100th of the LC50 shows minimal to no stress response. Overall, this study provides valuable insights into the toxicity and physiological responses of fish exposed to poultry waste biosynthesized AgNPs, offering potential applications in aquaculture while harnessing their unique features.

Release behavior and bioefficacy of imazethapyr formulations based on biopolymeric hydrogels.

Controlled release formulations of imazethapyr herbicide have been developed employing guar gum-g-cl-polyacrylate/bentonite clay hydrogel composite (GG-HG) and guar gum-g-cl-PNIPAm nano hydrogel (GG-NHG) as carriers, to assess the suitability of biopolymeric hydrogels as controlled herbicide release devices. The kinetics of imazethapyr release from the developed formulations was studied in water and it revealed that the developed formulations of imazethapyr behaved as slow release formulations as compared to commercial formulation. The calculated diffusion exponent (n) values showed that Fickian diffusion was the predominant mechanism of imazethapyr release from the developed formulations. Time for release of half of the loaded imazethapyr (t1/2) ranged between 0.06 and 4.8 days in case of GG-NHG and 4.4 and 12.6 days for the GG-HG formulations. Weed control index (WCI) of GG-HG and GG-NHG formulations was similar to that of the commercial formulation and the herbicidal effect was observed for relatively longer period. Guar gum-based biopolymeric hydrogels in both macro and nano particle size range can serve as potential carriers in developing slow release herbicide formulations.

Bioaccumulation of Potentially Toxic Elements in Commercially Important Food Fish Species from Lower Gangetic Stretch: Food Security and Human Health Risk Assessment.

Ganga river is the inhabitant of more than 190 fish species and important river system of India. Potentially toxic elements (PTEs) in the Gangetic riverine ecosystem are a hot environmental issue. A detailed evaluation of PTEs bioaccumulation in Gangetic fishes is required to safeguard human health. The present study investigated the bioaccumulation of PTEs (Cd, Co, Cr, Cu, Li, Ni, Pb, Se, Zn, and Mn) within 12 economic fish species (n = 72) collected from the lower Gangetic stretch. The mean concentrations of PTEs followed the order Zn > Cu > Mn > Ni > Se > Cr > Pb > Co ~ Li > Cd. Li and Se bioaccumulation were studied first time from Gangetic fishes. Results demonstrated that all the selected PTEs were below the maximum permissible limit recommended by reference standards except for Zn in L. catla and L. rohita. For all PTEs, the metal pollution index (MPI), hazard quotient (THQ), and hazard index (HI) were < 1, indicating that these PTEs do not pose a health risk to the public through the dietary intake of fish in this study area. All studied fish were acceptable in terms of carcinogenic risk (CR) from exposure to Cd, Cr, and Pb. Multivariate statistical analysis suggests that inter-correlated metals have similar dispersion properties and bioaccumulation homology within the body. This study provides a scientific basis for food safety assessment and continuous monitoring of PTEs in Gangetic fishes is suggested in the future to safeguard human health.

Bioaccumulation of arsenic in fish (Labeo rohita) in presence of periphyton: ameliorative effect on oxidative stress, physiological condition, immune response and risk assessment.

The present study explores the use of periphyton to ameliorate toxic properties of arsenic (As) to Labeo rohita and also assesses the human food safety aspects. Fish were introduced to arsenite [As(III)] contaminated water (0.3 and 3 mg/L) along with periphyton. Biochemical, physiological and immunological parameters, including gene expression, were assessed after 30 days of exposure. Periphyton incorporation significantly improved (p < 0.05) the adverse effects of As on respiration, NH3 excretion and brain AChE activity by reducing oxidative stress and As bioaccumulation. The presence of periphyton in As(III) exposed fish (3 mg/L) increased the immune response (Immunoglobulin M and Complement C3) in the serum and the regulation of the respective immune genes in the anterior kidney was found to be similar to the control. A speciation study using LC-ICP-MS confirmed the high accumulation of As by periphyton (5.0-31.9 µg/g) as arsenate [As (V)], resulting in a lower amount of As in fish muscle. The calculated human health risk indices, Target Hazard Quotient (THQ) and Target Cancer risk (TCR) indicate that fish grown in periphyton-treated water may lower the human health risks associated with As. The study signifies the importance of periphyton-based aquaculture systems in As contaminated regions for safe fish production with enhanced yield.

Toxic Metal Element Concentration in 31 Food Fishes from River Ganga: Risk Assessment on Human Consumption.

Consumption of toxic metal contaminated fish is a significant risk to human health. The Ganga river is one of the vital river systems in India, and it nurtures a rich biodiversity of flora and fauna. In the present study, screening of potential toxic metal elements (Cd, Cr, Mn, Cu, Pb, Ni, Zn, and As) was undertaken in 31 food fishes, especially the small indigenous fishes (SIFs) from the lower stretch of river Ganga by inductively coupled plasma mass spectrometry (ICP-MS). The concentration of toxic metal elements varied among different fish species. Among the toxic metal elements studied, Cr, Zn, and As were found to be dominant in Eleotris fusca; Cd, Ni, and Pb were highest in Securicula gora; Cu was highest in Cabdio morar; and Mn was highest in Coilia dussumieri. The average pollution load index values (APLI) for all the fishes analyzed were less than one except for Eleotris fusca, which indicated no serious toxic metal element pollution load. The estimated daily intake values (EDI) for the toxic metal elements were found to be within the permissible maximum tolerable daily intake (MTDI). Among the fishes studied, only a few species showed hazard index (HI) greater than one, indicating non-carcinogenic health risks. Similarly, the target carcinogenic values (TCR) for most of the toxic metal elements were below the permissible limit (10-4) in the fishes that assures minimal cancer risk. This study provides a comprehensive data on the composition of potential toxic metal elements of 31 food fishes from the lower stretch of the river Ganga, the first of its kind, and suggests the necessity of periodic monitoring of these in the aquatic ecosystem.

Biogenic synthesis of silver nanoparticle by Cytobacillus firmus isolated from the river sediment with potential antimicrobial properties against Edwardsiella tarda.

The aquatic environment, independent of their host, is more favorable to pathogenic bacteria than the terrestrial environment. Consequently, pathogenic bacteria can reach very high densities around aquatic animals and can cause high mortality. The conventional approach, such as antibiotics, has minimal effectiveness. Additionally, due to the emergence of (multiple) resistance, their use is under intense scientific and public scrutiny. Hence, there is a need for the development of alternative control techniques, with an emphasis on prevention, which is likely to be more cost-effective. In this study, a potential bacterial strain Cytobacillus firmus was isolated from polluted river sediment and characterized using a comprehensive range of techniques including biochemical, 16S rRNA sequencing and antibiogram assay. The pathogenicity of the bacteria was tested in vivo on Labeo rohita fingerlings found as non-pathogenic. Further, the bacteria were found to synthesize silver nanoparticles (AgNPs) using AgNO3 as a substrate. The obtained AgNPs were characterized by various methods, including UV-vis spectroscopy, FTIR (Fourier-transform infrared spectroscopy), and Transmission Emission Microscopy (TEM). The study found that the AgNPs were 20 nm in size on average. The antimicrobial activity of synthesized AgNPs was examined against the model freshwater pathogenic bacteria, Edwardsiella tarda and both the MIC (Minimum Inhibitory Concentration) and MBC (Minimum Bactericidal Concentration) were 0.156 µM, while biofilm inhibition activity was also observed at 0.156 µM. The AgNPs showed no haemolytic activity at 0.313 µM. Our findings suggest that C. firmus mediated bacteriogenic AgNPs modulate the activity of common pathogenic bacteria E. tarda. The thoroughness of our research process gives us confidence in the potential of applying AgNPs in aquaculture as a considerable strategy to control the E. tarda infection.

Metagenomic landscape of sediments of river Ganga reveals microbial diversity, potential plastic and xenobiotic degradation enzymes.

The Ganga is the largest river in India, serves as a lifeline for agriculture, drinking water, and religious rites. However, it became highly polluted due to the influx of industrial wastes and untreated sewages, leading to the decline of aquatic biodiversity. This study investigated the microbial diversity and plastic-xenobiotic degrading enzymes of six sediment metagenomes of river Ganga at Prayagraj (RDG, TSG, SDG) and Devprayag (KRG, BNG, BRG). The water quality parameters, higher values of BOD (1.8-3.7 ppm), COD (23-29.2 ppm) and organic carbon (0.18-0.51%) were recorded at Prayagraj. Comparative analysis of microbial community structure between Prayagraj and Devprayag revealed significant differences between Bacteroidetes and Firmicutes, which emerging as the predominant bacterial phyla across six sediment samples. Notably, their prevalence was highest in the BRG samples. Furthermore, 25 OTUs at genus level were consistent across all six samples. Alpha diversity exhibited minimal variation among samples, while beta diversity indicated an inverse relationship between species richness and diversity. Co-occurrence network analysis established that genera from the same and different groups of phyla show positive co-relations with each other. Thirteen plastic degrading enzymes, including Laccase, Alkane-1 monooxygenase and Alkane monooxygenase, were identified from six sediment metagenomes of river Ganga, which can degrade non-biodegradable plastic viz. Polyethylene, Polystyrene and Low-density Polyethelene. Further, 18 xenobiotic degradation enzymes were identified for the degradation of Bisphenol, Xylene, Toluene, Polycyclic aromatic hydrocarbon, Styrene, Atrazene and Dioxin etc. This is the first report on the identification of non-biodegradable plastic degrading enzymes from sediment metagenomes of river Ganga, India. The findings of this study would help in pollution abatement and sustainable management of riverine ecosystem.

Cr-Detector: A simple chemosensing system for onsite Cr (VI) detection in water.

Due to the increase in urbanization and industrialization, the load of toxicants in the environment is alarming. The most common toxicants, including heavy metals and metalloids such as hexavalent Chromium, have severe pathophysiological impacts on humans and other aquatic biotas. Therefore, developing a portable rapid detection device for such toxicants in the aquatic environment is necessary. This work portrays the development of a field-portable image analysis device coupled with 3,3',5,5'-tetramethylbenzidine (TMB) as a sensing probe for chromium (VI) detection in the aquatic ecosystem. Sensor parameters, such as reagent concentration, reaction time, etc., were optimized for the sensor development and validation using a commercial UV-Vis spectrophotometer. The chemoreceptor integrated with a uniform illumination imaging system (UIIS) revealed the system's applicability toward Cr(VI) detection. The calibration curve using the R-value of image parameters allows Cr(VI) detection in the linear range of 25 to 600 ppb, which covers the prescribed permissible limit by various regulatory authorities. Furthermore, the adjusted R2 = 0.992 of the linear fit and correlation coefficients of 0.99018 against the spectrophotometric method signifies the suitability of the developed system. This TMB-coupled field-portable sensing system is the first-ever reported image analysis-based technology for detecting a wide range of Cr(VI) in aquatic ecosystems to our knowledge.

Bioaccumulation of polystyrene microplastics and changes in antioxidant and AChE pattern in a freshwater snail (Filopaludina bengalensis) from river Ganga.

Microplastic pollution is a leading global problem affecting terrestrial and marine aquatic ecosystems. Due to the stagnant nature of microplastics, the toxic effect of microplastics is more pronounced to benthic organisms than the surface feeder. Hence, the present study effort was to study the microplastic bioaccumulation pattern and changes in the enzymatic and nonenzymatic antioxidant and AChE pattern of freshwater snail Filopaludina bengalensis, which were subjected to 0.5 ppm to 5 ppm levels of polystyrene microsphere (∼ 30 µm) for 27 days. The study showed that microplastics were easily accumulated in the test organism in a dose and time-dependent manner, amounting to 82 ± 6.02 particles /individuals at a 5 ppm dose on the 27th day. However, no mortality was observed at the test microplastic dosages. The enzymatic antioxidant profile (SOD and catalase) showed limited variability and remained stable with increased duration and microplastic dose. However, the nonenzymatic antioxidant profile showed distinct variability with the complete seizing of the DPPH activity on the 27th day at 5 ppm microplastic dose and a gradual decrease of ABTS and FRAP activity at all the dose ranges. Even the AChE activity decreased with higher exposure concentrations. The present study for the first time shows the direct impact of microplastics on a freshwater snail widely available in the Indian subcontinent, indicating the role of microplastic pollution will create havoc in the Ganga river eco-biosystem in the long run.

Ameliorative effect of natural floating island as fish aggregating devices on heavy metals distribution in a freshwater wetland.

Growing human population and climate change are leading reasons for water quality deterioration globally; and ecologically important waterbodies including freshwater wetlands are in a vulnerable state due to increasing concentrations of pollutants like heavy metals. Given the declining health of these valuable resources, the present study was conducted to evaluate the effect of natural floating island in the form of fish aggregating devices (FADs) made of native weed mass on the distribution of heavy metals in the abiotic and bio compartments of a freshwater wetland. Lower concentrations of surface water heavy metals were observed inside the FADs with a reduction of 73.91%, 65.22% and 40.57-49.16% for Cd, Pb and other metals (viz. Co, Cr, Cu, Ni and Zn), respectively as compared to outside FAD. These led to 14.72-55.39% reduction in the heavy metal pollution indices inside the FAD surface water. The fish species inside the FADs were also found less contaminated (24.07-25.07% reduction) with lower health risk indices. The study signifies the valuable contribution of natural floating island as FADs in ameliorating the effect of heavy metals pollution emphasizing the tremendous role of the natural floating islands in sustainable maintenance of freshwater wetlands for better human health and livelihood.

Aptamer-based NanoBioSensors for seafood safety.

Chemical and biological contaminants are of primary concern in ensuring seafood safety. Rapid detection of such contaminants is needed to keep us safe from being affected. For over three decades, immunoassay (IA) technology has been used for the detection of contaminants in seafood products. However, limitations inherent to antibody generation against small molecular targets that cannot elicit an immune response, along with the instability of antibodies under ambient conditions greatly limit their wider application for developing robust detection and monitoring tools, particularly for non-biomedical applications. As an alternative, aptamer-based biosensors (aptasensors) have emerged as a powerful yet robust analytical tool for the detection of a wide range of analytes. Due to the high specificity of aptamers in recognising targets ranging from small molecules to large proteins and even whole cells, these have been suggested to be viable molecular recognition elements (MREs) in the development of new diagnostic and biosensing tools for detecting a wide range of contaminants including heavy metals, antibiotics, pesticides, pathogens and biotoxins. In this review, we discuss the recent progress made in the field of aptasensors for detection of contaminants in seafood products with a view of effectively managing their potential human health hazards. A critical outlook is also provided to facilitate translation of aptasensors from academic laboratories to the mainstream seafood industry and consumer applications.

Trophic transfer patterns of arsenic in freshwater ecosystem layers in arsenic-endemic Ganges Delta and its potential human health risk.

Arsenic (As) is a toxic environmental contaminant with global public health concern. In aquatic ecosystems, the quantification of total As is restricted chiefly to the individual organisms. The present study has quantified the total As in different trophic layers (sediment-water-phytoplankton-periphyton-zooplankton-fish-gastropod-hydrophytes) of lentic freshwater ecosystems. As transfer pathways quantifying the transmission rate across trophic-level compartmental route were delineated using a novel model-based approach along with its potential contamination risk to humans. Lentic water bodies from Indo-Gangetic region, a core area of groundwater As, were selected for the present investigation. The study revealed that among the lower biota, zooplankton were the highest accumulator of total As (5554-11,564 µg kg-1) with magnification (rate = 1.129) of the metalloid, followed by phytoplankton (2579-6865 µg kg-1) and periphytic biofilm (1075 to 4382 µg kg -1). Muscle tissue of zooplanktivore Labeo catla is found to store higher As (80-115 µg kg-1 w.w.) compared to bottom-dwelling omnivore Cirrhinus mrigala (58-92 µg kg-1 w.w.). Whereas, Amblypharyngodon mola has accumulated higher As (203-319 µg kg-1 w.w.) than Puntius sophore (30-98 µg kg-1 w.w.) that raised further concern. The hepatic concentration indicated arsenic-mediated stress based on As stress index (threshold value = 1). Mrigal and Mola showed significant biomagnification among fishes while biodiminution was observed in Catla, Bata, Rohu and Punti. All the studied fishes were under the arsenic mediated stress. In the 'sediment-water-periphytic biofilm-gastropod' compartment, the direct grazing accumulation was higher (rate = 0.618) than the indirect path (rate = 0.587). Stems of edible freshwater macrophytes accumulated lesser As (32-190 µg kg-1 d.w.) than roots (292-946 µg kg-1 d.w.) and leaves (62-231 µg kg-1 d.w.). The target cancer risk (TCR) revealed a greater concern for adults consuming edible macrophyte regularly. Similarly, the varied level of target hazard quotient and TCR for adults consuming fishes from these waterbodies further speculated significant health concerns. The trophic transfer rate of environmental As in soil-water-biota level at an increasing trophic guild and consumer risk analysis have been unravelled for the first time in the Indo-Gangetic plains, which will be helpful for the strategic mitigation of As contamination.

Release kinetics of controlled release formulations of thiamethoxam employing nano-ranged amphiphilic PEG and diacid based block polymers in soil.

Amphiphilic copolymers, synthesized from poly(ethylene glycols) and various aliphatic and aromatic diacids, which self-assemble into nanomicellar aggregates in aqueous media, were used to develop controlled release (CR) formulations of thiamethoxam (3-(2-chloro-1,3-thiazol-5-ylmethyl)-5-methyl-1,3,5-oxadiazinan-4-ylidene(nitro)amine) using encapsulation technique Formulations were characterised by Infrared (IR) spectroscopy, Dynamic Light Scattering (DLS) and Transmission Electron Microscope (TEM). Encapsulation efficiency, loading capacity and stability after accelerated storage test of the developed formulations were checked. The kinetics of thiamethoxam, released in sandy loam soil from the different formulations was studied. Release from the commercial formulation was faster than the CR formulations. The time taken for release of 50 % of thiamethoxam ranged from 3.56 to 6.07 days for the CR formulations. Although the diffusion exponent (n value) of thiamethoxam in soil ranged from 0.532 to 0.881 in the tested formulations showing non-Fickian transport. These CR formulations may be used in safer, effective and economic crop protection.

Antibacterial properties and in silico modeling perspective of nano ZnO transported oxytetracycline-Zn2+ complex [ZnOTc]+ against oxytetracycline-resistant Aeromonas hydrophila.

Emergence of antibiotics resistance has threatening consequences not only for human health but also for animal health issues in agriculture. Several animal pathogenic bacteria have developed antibiotic resistance and managing same has tremendous cost repercussions and may lead to total harvest loss. Hence in the present study, efforts are made to revitalize an old antibiotic molecule, oxytetracycline (OTc), through nanodelivery approaches using zinc oxide nanoparticles (nZnO) to confront OTc resistant fish pathogenic bacteria Aeromonas hydrophila. OTc was impregnated in nZnO through in situ precipitation method to develop OTc loaded ZnO nanoparticles (OTc@nZnO) with average size of 99.42 nm. Spectroscopic investigation of same revealed complexation of Zn2+ with amide and aromatic carbonyl moieties of OTc [ZnOTc]+. The complex performed better against A. hydrophila with 7-15 mm inhibition zone as compared to nil for bare OTc at same dose. OTc also showed MIC of 150 µg ml-1 and for OTc@nZnO it was 7.02 µg ml-1 with faster killing rate (k, -0.95). In silico docking simulation suggest that [ZnOTc]+ had low binding affinity (LBE > -5.00 kcal mol-1) toward TetR(E) and TetA(E) proteins of A. hydrophila as compared to OTc (LBE < -8.00 kcal mol-1). This study postulates that [ZnOTc]+ released from OTc@nZnO can escape TetR(E) and TetA(E) resistance proteins and bind at 30S ribosomal subunit with high affinity (<-11.00 kcal mol-1) to exert antibacterial properties. In the recent scenario of recurrent antimicrobial resistance, the develop antibiotic-nanocomposites could come out as potential solution, however further study is required for its feasibility for use in animal health care.

Pollution assessment and mapping of potentially toxic elements (PTE) distribution in urban wastewater fed natural wetland, Kolkata, India.

East Kolkata Wetland (EKW) is one of the largest sewage-fed wetlands in the world, which support the livelihood of thousands of peoples. However, at present, EKW system has become ecologically vulnerable due to the discharge of toxic waste through the sewage canal from the Kolkata metropolitan city. Hence, it becomes very important to understand the inflow and load of potentially toxic elements (PTE) in the sediment, water, and fish of sewage-fed wetland used for aquaculture activities. In this study, one of the polluted wetland from EKW, Sardar bherry, was selected as the study area. Sediment samples (45) were collected from 15 sites to characterize the PTEs concentrations levels utilizing inductively coupled plasma mass spectrometry, and their spatial distribution pattern and pollution quality indices were estimated. Water (45) and fish (7) samples were also analyzed to understand the distribution pattern of PTEs from sediment to water and water to fish. The geostatistical prediction map showed that the concentration range of Cr, Fe, Cu, Co, Zn, Cd, Ni, Pb, and Mn in sampling stations were 27.3-84.1 µg g-1, 7281-30193 µg g-1, 50.6-229.7 µg g-1, 4.8-15.3 µg g-1, 113.4-776.9 µg g-1, 10.0-26.9 µg g-1, 23.8-55.7 µg g-1, 9.5-39.3 µg g-1, and 188.6-448.5 µg g-1 respectively. Pollution is alarming in sediment as all of the studied PTEs exceed the threshold effect level according to Sediment Quality Guidelines. Cd levels in sediments were found to be upper than the lowest effect level (LEL), probable effect level (PEL), threshold effect level (TEL), and severe effect level (SEL) for all sample locations. Several pollution assessment indexes (contamination factor, geo-accumulation index, ecological risk index, etc.) also showed that sediment samples were severely polluted by Cd. PTEs status in water and fish is within permissible limits. The study emphasizes that attention should be paid to controlling the excessive accumulation of PTEs in sediment that would further harm the ecological environment and ultimately human health.

Taxonomic profiling and functional gene annotation of microbial communities in sediment of river Ganga at Kanpur, India: insights from whole-genome metagenomics study.

The perennial river Ganga is recognized as one of India's largest rivers of India, but due to continuous anthropogenic activities, the river's ecosystem is under threat. Next-generation sequencing technology has transformed metagenomics in the exploration of microbiome and their imperative function in diverse aquatic ecosystems. In this study, we have uncovered the structure of community microbiome and their functions in sediments of river Ganga at Kanpur, India, at three polluted stretches through a high-resolution metagenomics approach using Illumina HiSeq 2500. Among the microbes, bacteria dominate more than 82% in the three polluted sediment samples of river Ganga. Pseudomonadota (alpha, beta, and gamma) is the major phylum of bacteria that dominates in three sediment samples. Genes involved in degradation of xenobiotic compounds involving nitrotoluene, benzoate, aminobenzoate, chlorocyclohexane, and chlorobenzene were significantly enriched in the microbiome of polluted stretches. Pathway analysis using KEGG database revealed a higher abundance of genes involved in energy metabolism such as oxidative phosphorylation, nitrogen, methane, sulfur, and carbon fixation pathways in the sediment metagenome data from the river Ganga. A higher abundance of pollutant degrading enzymes like 4-hydroxybenzoate 3-monooxygenase, catalase-peroxidase, and altronate hydrolase in the polluted microbiome indicates their role in degradation of plastics and dyes. Overall, our study has provided bacterial diversity and their dynamics in community structure and function from polluted river microbiome, which is expected to open up better avenues for exploration of novel functional genes/enzymes with potential application in health and bioremediation.

Community structure and function of microbiomes in polluted stretches of river Yamuna in New Delhi, India, using shotgun metagenomics.

The large population residing in the northern region of India surrounding Delhi mostly depends on water of River Yamuna, a tributary of mighty Ganga for agriculture, drinking and various religious activities. However, continuous anthropogenic activities mostly due to pollution mediated by rapid urbanization and industrialization have profoundly affected river microflora and their function thus its health. In this study, potential of whole-genome metagenomics was exploited to unravel the novel consortia of microbiome and their functional potential in the polluted sediments of the river at Delhi. Analysis of high-quality metagenome data from Illumina NextSeq500 revealed substantial differences in composition of microbiota at different sites dominated by Proteobacteria, Bacteroidetes, Firmicutes, Actinobacteria and Chloroflexi phyla. The presence of highly dominant anaerobic bacteria like Dechloromonas aromatica (benzene reducing and denitrifying), Rhodopseudomonas palustris (organic matter reducing), Syntrophus aciditrophicus (fatty acid reducing) and Syntrophobacter fumaroxidans (sulphate reducing) in the polluted river Yamuna signifies the impact of unchecked pollution in declining health of the river ecosystem. A decline in abundance of phages was also noticed along the downstream river Yamuna. Mining of mycobiome reads uncovered plethora of fungal communities (i.e. Nakaseomyces, Aspergillus, Schizosaccharomyces and Lodderomyces) in the polluted stretches due to the availability of higher organic carbon and total nitrogen (%) could be decoded as promising bioindicators of river trophic status. Pathway analysis through KEGG revealed higher abundance of genes involved in energy metabolism (nitrogen and sulphur), methane metabolism, degradation of xenobiotics (Nitrotoluene, Benzoate and Atrazine), two-component system (atoB, cusA and silA) and membrane transport (ABC transporters). Catalase-peroxidase and 4-hydroxybenzoate 3-monooxygenase were the most enriched pollution degrading enzymes in the polluted study sites of river Yamuna. Overall, our results provide crucial insights into microbial dynamics and their function in response to high pollution and could be insightful to the ongoing remediation strategies to clean river Yamuna.

Sustainable biodiesel production from microalgae Graesiella emersonii through valorization of garden wastes-based vermicompost.

Biodiesel production from microalgae has gained significant interest recently due to the growing energy demand and non-renewable nature of petroleum. However, high cost of production and environmental health related issues like excess use of inorganic fertilizers, eutrophication are the major constraints in commercial-scale biodiesel production. Besides this, solid wastes (garden-based) management is also a global concern. In the present study, to overcome these limitations vermicompost extract was tested as nutrient source to enhance growth performance and lipid production from a freshwater microalga (Graesiella emersonii MN877773). Garden wastes were first converted into vermicompost manure and its extract (aerobic and anaerobically digested) was prepared. The efficacy of the extract was then tested in combination with BG11 medium. The mixotrophic cultivation of microalgae in anaerobically digested vermicompost extract at 50:50 combination with BG11 medium enhanced the cell biomass (0.64 g d. wt. L-1) and lipid productivity (3.18 mg L-1 day-1) of microalgae by two times. Moreover, the combination also improved the saturated (methyl palmitate) and monounsaturated fatty acids (oleic acid) content in the test algae. The quality of biodiesel also complies with all the properties of biodiesel standard provided by India, the USA, and Europe except the cold filter plugging property. The combination was also found to improve the cell biomass (0.041 g L-1) as compared to BG11 medium in mass-scale cultivation. Hence, the study proved that G. emersonii grown in media supplemented with garden waste-based vermicompost extract had significant potential for mass-scale biodiesel and bioproduct production.

Arsenic Bioaccumulation and Identification of Low-Arsenic-Accumulating Food Fishes for Aquaculture in Arsenic-Contaminated Ponds and Associated Aquatic Ecosystems.

Arsenic-contaminated food including farmed fish is one of the main routes of human exposure. Fish farmed in contaminated environment accumulates arsenic in different tissues with great variability. Thus, it is utmost important to quantify the risk associated with different farmed fish species in arsenic-contaminated aquaculture systems. In the present study, arsenic content was measured in twelve fish species (Labeo rohita, L. catla, Cirrhinus mrigala, Oreochromis niloticus, O. mossambicus, Liza tade, Puntius javanicus, L. calbasu, Glossogobius giuris, Macrobrachium rosenbergii, Ctenopharyngodon idella, and Bellamya bengalensis (gastropod)) collected from arsenic-contaminated aquaculture systems. Among the studied finfishes, C. idella was found to accumulate the lowest amount of arsenic (< 0.05 ± 0.00 mg kg-1) whereas the highest accumulation was noticed in O. mossambicus (1.0 ± 0.18 mg kg-1). However, the estimated carcinogenic and non-carcinogenic risks of human were found to be low for all the studied fishes. The calculated target hazard quotient (THQ) value for adults ranged from 0.01 to 0.08 whereas for children it ranged from 0.05 to 0.27 for low-arsenic-accumulating fishes (arsenic conc. < 0.5 mg kg-1). Based on these findings, C. mrigala, C. idella, and M. rosenbergii could be recommended as the candidate species for aquaculture in the arsenic-contaminated areas as farming of the low-arsenic-accumulating food fishes would also lower the risk of human exposure through food chain.