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Despite major advances in biosensing, quick, dependable, and effective on-site detection of bacterial infections remains a serious issue, owing to a lack of acceptable or appropriate diagnostic platforms. To address this gap, we presented a new colorimetric gold NanoZyme aptasensor for rapid sensing of Aeromonas veronii, an infectious bacterial disease in fish. The A. veronii-specific aptamer (AVS01) was developed through Cell-SELEX. The sensing mechanism involves inhibition of AuNPs induced peroxidase-mimic catalytic activity through surface adsorption by AVS01 which in the presence of the A. veronii desorb from the AuNPs allowing recovery of the catalytic activity leading to colorimetric response, whereas the sensor is insesnsitive to other nontarget bacterial cells. This method is very specific and sensitive, allowing for the quick and visible sensing of A. veronii with a detection limit of 1281 CFU mL−1 within 15 min. The method has great potential for rapid diagnosis of bacterial infection in fish caused by A. veronii.

Spermiation, an act of sperm release, depends on several molecular factors. Despite hormonal administration, spermiation failure is a primary concern in certain fishes. In this study, the molecular mechanisms of spermiation have been analyzed in Cyprinus carpio by comparative transcriptomics. Unigenes for C. carpio control (CCC), which were injected with PBS (Phosphate-buffered saline), and C. carpio treated (CCT), which were injected with ovatide, were 107,616 and 133,435, respectively. A total of 93 genes were identified as involved in the spermiation process, including those related to gonadal steroidogenesis, cell growth, cell adhesion, and cytoplasmic matrix formation. The cd63, CENPS, rasa1a, and genes for gonad steroidogenesis, cell growth, cell adhesion, and cytoplasmic matrix formation were analyzed. Gene expression analysis revealed tubulobulbar complexes mediated disengagement of spermatozoa and JAK2 signaling regulated cyst breakage in teleost for the first time. Analysis was done from the changes at the molecular level to the final act of spermiation. Tissue histology analysis was conducted in accordance with the molecular study, which showed structural changes. Induced breeding in fish plays a key role in seed production in aquaculture sector. However, there are several constraints the sector is still facing due to lack of extensive knowledge regarding the mechanisms of spermiation and species-specific response to hormonal dosage. This study is relevant to understand the molecular mechanisms involved in spermiation and the stages which mark as critical point of sperm release after administrating the inducing agent. This study also lays the groundwork for further exploration of species-specific responses to hormonal treatments, aiding sustainable seed production in the fisheries sector.

Plastic waste has become a significant global ecological concern due to its substantial harmful impacts. They are eventually colonized and transformed by diverse microbial communities known as the ‘‘plastisphere”. Only a limited group of microbes have been identified so far due to the prevalence of non-culturable strains that inhabit polymer substrates. We investigated the community diversity and predictive functionality of the plastisphere microbiota using a high-throughput next-generation sequencing (NGS) approach to unveil their plastic degrading potential. Samples were collected from four different plastic-enriched disposal sites adjacent to Kolkata, West Bengal, India, followed by processing, gDNA extraction, library preparation, and sequencing. The most prevalent phyla were Proteobacteria, followed by Bacteroidetes, Actinobacteria, Cyanobacteria, Firmicutes, and Verrucomicrobia. The functional profiling revealed that genes associated with metabolism, cellular processes, and signalling were most prevalent, followed by poorly characterized information storage and processing. In this study, we predicted the existence of a beneficial microbiome associated with bioremediation and plastic degradation, which suggests the potential utilization of plastics as primary carbon sources. Our findings also highlighted the existence of promising microbial enzymes associated with the biodegradation of several plastic substrates.Furthermore, our research unveiled the enriched distribution of beneficial microbiome in the studied metagenome, which offers a diverse prospect. This investigation establishes a connection between the structure of microbial communities and diverse genes actively engaged in the biodegradation of plastic waste within plastic disposal sites. These beneficial degraders can be investigated further for broad-spectrum applications in plastic bioremediation. Subsequent explorations of their plastic degrading enzymes will provide profound contributions to plastic pollution mitigation.

Hexavalent chromium or Cr(VI) is highly toxic for humans as it causes high oxidative reactions inside cells, leading to diseases like chronic ulcers and damage to the kidneys, mucous membranes, throat, skin, and respiratory tract. Due to rapid urbanization, Cr(VI) comes into our food chain through unmonitored and uncontrolled application in agriculture fields, refineries, mills, the tanning industry, automobiles, road works, etc. Presently, the standard Cr(VI) detection is done using conventional processes, which, though accurate, has severe drawbacks in on-the-spot rapid detection in the field. Here, we have represented a handheld potentiostat towards trace-level Cr(VI) detection in aquatic environments. A Cr(VI) specific DNA aptamer immobilized screen printed electrode (SPE) has been used as the main biosensor. The device operates on an electronic peak current dumping event through mass deposition in the presence of an aptamer coupled with Cr(VI) onto the working electrode. The working range of the developed prototype is in the range of 0–1000 ppb Cr(VI), where the maximum linearity has been observed in the range of 0–500 ppb with a limit of Detection (LOD) as low as 10 ppb. The device has exhibited an excellent correlation with commercially available electrochemical workstations with a coefficient of 0.972. Moreover, the applicability of the developed device has been validated for 7 different types of water samples. To our knowledge, this is the first-ever reported simplistic resource-limited on-spot aptasensing device for Cr(VI) detection in an aquatic environment.

The river Ganges in India has faced considerable issues due to water quality degradation caused by various anthropogenic activities. This study employs metagenomic analysis to comprehensively characterize bacterial communities, explore functional genomics, and investigate the prevalence of virulence factors and antibiotic resistant genes (ARGs) within the sediment environment of the river Ganges. Taxonomic profiling revealed that Proteobacteria were the most dominating phyla found in all samples, whereas the abundance of Pseudomonas at the genus level was the highest in all the samples. Functional annotation and pathway analysis uncover the genomic potential of sediment associated bacteria, shedding light on metabolic pathways, biogeochemical processes, human diseases and adaptive mechanisms within the riverine ecosystem. Moreover, identifying the highest number of genes related to virulence factors was observed in K1 samples (3), and the highest number of genes related to ARGs found in K3 (25) samples emphasizes the need to understand potential pathogenicity in these environments. Characterization of ARGs provides crucial insights into the prevalence of resistance determinants, their genetic contexts, and potential sources of antibiotic resistance in this vital aquatic ecosystem. Overall metagenomics analysis in different sampling sites of river Ganga observed nearly the same OTUs at microbial communities at the taxonomic level but not at a functional level. This research can be a critical foundation for assessing the ecological implications of microbial communities, functional genomics, and the resistome in the river Ganges sediments. The findings underscore the importance of metagenomic approaches in elucidating the intricate microbial ecology and the prevalence of genetic elements relevant to environmental health and antimicrobial resistance in aquatic ecosystems. Further investigation would be required to understand the underlying cause behind the restoration of microbial functional profiles, including ARGs and VFs, to unravel the rejuvenation aspects of this unique ecosystem.

To delineate the response mechanism of Nile tilapia (Oreochromis niloticus) to the riverine pollution of river Ganga, a comparative transcriptomic analysis was performed utilizing fresh liver through RNA-Seq technology. A total of 51.39 million and 32.8 million reads were obtained after excluding low quality sequences from non-polluted (Barrackpore) and polluted (Kanpur) sites of Nile tilapia. About 81.4 % and 95.3% reads were perfectly mapped with the reference sequence of O. niloticus. Transcriptional analysis generated 363 differential expressed genes (DEGs) including 131 up-regulated and 232 down-regulated genes. Gene Ontology (GO) enrichment analysis revealed that significant DEGs were associated with ribosome biogenesis, alpha-amino acid metabolic process, translational initiation etc. as biological process (BP); unfolded protein binding, vitamin binding, carboxylic acid binding and etc. as molecular function (MF); ribosome, and ribosomal subunit as cellular component (CC). The KEGG analysis indicated that these DEGs were highly involved in ribosome, Lysine degradation and RNA transport pathways. Additionally, ten hub genes participated in Translation, Ribonucleoprotein complex biogenesis as BP, Ribosome, Eukaryotic translation initiation factor 3 complex as CC and Structural constituent of ribosome, RNA binding as MF were affected in riverine pollution. Overall, this transcriptome investigation provided an extensive overview of pollution triggered transcriptional mechanisms in Tilapia liver and would be highly significant for further exploration of the molecular processes in response to pollution.

The current study aimed at assessing the immunostimulatory properties of silver nanoparticles (AgNPs) on Labeo rohita, and understanding how it affects the growth, cellular ultrastructure, the expression level of immune genes, and infection risk from Aeromonas hydrophila. Fish (avg wt: 30.1±3.26 g) were fed diets with four separate AgNP inclusion levels (0 µgKg−1 [basic diet, T1], 10 µgKg−1 [T2], 15 µgKg−1 [T3], and 20 µgKg−1 [T4]) for 56 days. After the feeding trial, growth, histological, immunological parameters, and protective immune response against A. hydrophila were assessed. The fish in the treatment groups including T1(control), the T3 growth indices, such as specific growth rate (7.56±0.26) and percent weight gain (231.05±3.21), was statistically higher (P < 0.05). In the immunological and oxidative parameters, levels of SOD and catalase decreased in correlation with a rise in the inclusion doses of AgNP in the liver, and a reduction in catalase values was recorded in the gill. With the addition of AgNP, the NBT value was decreased in the gill, and T3 had a considerably larger (P

Wetlands are recognized as one of the most productive aquatic ecosystems. This high productivity supports its enormous biodiversity, aiding a scope for the small scale fisheries within it. Basically, these wetlands act as platforms for culture-based fisheries (CBF) i.e practice of stocking fish seeds and harvesting the grow out fishes at later. Often in tropical wetlands, the high nutrient load and high temperature enable the luxurious growth of macrophytes. Moreover, this macrophyte infestation is considered as a bottleneck for wetland managers. Facing a similar situation our studied Beledanga wetland is a macrophyte-infested wetland and the invasive Eichhornia crassipes is the most dominant macrophyte species. Owing to the macrophyte problem, Grass carp have been stocked in it as a biocontrol agent, as grass carp is a known biocontrol agent for the macrophyte infestation situation and simultaneously it will raise the fish production. To ensure maximum sustainable production from the wetland by harnessing with the available resources, it is necessary to acquire knowledge about the system’s ecological status and its ecological networks. Thus, the Ecopath based mass-balanced model is one of the best suitable tools to know about the ecological organization of this Beledanga wetland. Considering the available data (observational and literature data), this study has constructed a mass-balanced Ecopath model with 14 functional groups including all fish groups, birds, plankton, benthos and detritus. It has been found that the zooplankton and benthos are the most utilized group and the birds are the keystone group in this wetland system. This wetland possesses a lower transfer efficiency as well as a low Finn’s cycling index (0.224%). The system is found as an immature system with moderate ascendancy and system reserve (overhead). Moreover, concerning the ecologically sustainable production from this wetland more virtual mass-balanced models were developed (i) to evaluate the optimum grass carp stocking to manage the macrophyte population and (ii) to assess the impact of the Eichhornia on the system functioning. The results show that the system can harbour 1.5 times more grass carp biomass than the present without hampering sustainability. Concerning the impact of Eichhornia, it has been noticed that this macrophyte affects the maturity and transfer process of the system. Moreover, its huge biomass only accumulates more detritus in the ecosystem.

Edwardsiella tarda is one of the serious bacterial pathogens infecting both cultured and wild catfish urging an immediate need for effective protection strategies. This study assessed the effects of dietary supplementation of Pseudomonas aeruginosa FARP72 at 108 cells/g feed (PA diet) for 30 days on the innate immunity parameters, viz., respiratory oxidative burst (ROB) activity, lysozyme, ceruloplasmin, myeloperoxidase, in-vitro nitric oxide (NO) production in addition to the expression of immune genes encoding interleukin-1β, C3 and transferrin in yellowtail catfish Pangasius pangasius and their resistance to Edwardsiella tarda challenge at a sub-lethal dose of 1.50 × 107 cells/fish. A significant increase in the innate immunity parameters was noted in PA diet-fed catfish on 30 dpf compared to the control. Post E. tarda challenge, the levels of immune parameters increased significantly and peaked at 5 dpi irrespective of feeding to confer protection against E. tarda. Their levels, however, decreased on and from 10 dpi. The results on the expression of immune genes encoding interleukin-1β, C3 and transferrin in the kidney and liver tissue samples of PA diet-fed P. pangasius upon challenge with E. tarda further confirmed the ability of P. aeruginosa to stimulate primary immune organs at the gene level. The effects of feeding P. aeruginosa FARP72 on the immune functions of catfish as examined by the functional immune assays, thus, demonstrating the innate immune responses of catfish that are differentially stimulated by the PA diet. The findings of our study would help evolve management strategies to confer protection against E. tarda infection in commercial catfish aquaculture.

Acetylcholinesterase (AChE), a widely used enzyme for inhibition-based biosensors in pesticide residues detection, lags due to multiple-step operation, time-consuming incubation and reactivation/regeneration steps. Herein, this endeavour reports the development of Organophosphate Hydrolase (OPH), which has functional superiority over the AChE and explored in on-spot biosensing device for organophosphate pesticide residue detection in fruits and vegetables. The organophosphate degrading enzyme OPH is expressed from the ‘opd’ gene through biotechnological tools. The OPH exhibited its best activity at pH 8.0 and subsequently thermal inactivation over 37 °C. The activity of the purified OPH enzyme was found 2.75 U mL−1 at λmax 410 nm. Furthermore, the developed OPH is integrated into 96 well plate format with our previously reported UIISScan 1.1, an advanced imaging array technology based field-portable high-throughput sensory system. The developed biosensor revealed a linear range from 100 ng mL−1 to 0.1 ng mL−1 for detection of organophosphate pesticide residues with a negative slope i.e. y = 235.678x (ng mL−1) – 62.8725 with R2 = 0.99991 and n = 23. Moreover, the applicability of the developed biosensor was tested for market available fruits and vegetables. This is the first-ever reported OPH mediated on-spot biosensing device for pesticide residue detection in fruits and vegetables to the best of our knowledge.

Soil salinization has become a severe constraint for crop production world-wide which necessitated development or induced enhancement of salt stress tolerance in plant life to sustain production in saline lands. Recognition and prospecting of valuable stress tolerant genes from natural microbial resources of saline habitat is obscure to date. Therefore, the investigation was towards isolation and characterization of marine salt stress tolerant microbes along the East coast of India for revelation of effective salt stress tolerant genes. Salt stress tolerance was assessed from 98 bacterial isolates obtained from 28 water and soil samples. Among them, 35 isolates which failed to grow beyond 4% salt were discarded and remainder 63 isolates were selected for further functional analysis and only seven isolates recorded ≥8% NaCl stress tolerance. Phylogeny revealed that four isolates belong to Firmicutes and three isolates were members of Proteobacteria. Ribosomal Database Project Release-11 and SILVA SSU database based genotyping and taxonomic identity analysis confirmed that the higher (20%) salt stress tolerant bacteria were Staphylococcus sp., Enterococcus sp., Enterobacter sp. and Proteus sp. To investigate candidate, as well as, novel salt stress tolerant genes, the seven bacterial isolates would provide new horizon to focus on the recent developments of salinity stress tolerance. In addition, the findings evidently point out the diversity of salt stress tolerant marine bacteria in coastal Odisha and West Bengal, India.