Bromoform Toxicity to Marine Microalgae: Studies using the Diatom Chaetoceros lorenzianus as a Model Organism.

Bromoform is the most prominent, relatively long-lived chlorination by-product in condenser effluents from seawater-based power plant cooling systems. There are few reports on the potential toxicity of this trihalomethane to marine phytoplankton. We investigated this using a marine diatom, Chaetoceros lorenzianus as the model organism. The study was conducted by exposing the diatom to bromoform concentrations 0, 50, 100, 150, 250, 500 and 1000 µg/L for exposure time of 3 and 24 h. The mode of action of bromoform was examined using endpoints which include chlorophyll a fluorescence, cell viability by SYTOX® green stain and genotoxicity by comet assay. The relative fluorescence unit and percent viability changed significantly at all concentrations in duration of study. The 24-h IC50 for viability and chlorophyll was estimated to be 255.6 µg/L and 343.5 µg/L, respectively. The tail DNA of 5-20% observed by comet assay indicated low-level DNA damage. Bromoform manages to target cell membrane and internal machinery, DNA and chlorophyll molecule of cell, leading to cause damage at multiple physiological levels. Based on the present data, the current discharge levels of bromoform 50-250 µg/L cause significant impact on the phytoplankton under investigation. However, the impact can be limited under actual field conditions wherein mixing of cooling water with natural water bodies is considered. Nevertheless, more studies are required to understand the toxicological response of organisms to bromoform, so that discharge levels can be continued to be kept within safe levels.

Exploring biogenic chalcones as DprE1 inhibitors for antitubercular activity via in silico approach.

Cases of drug-resistant tuberculosis (TB) have increased worldwide in the last few years, and it is a major threat to global TB control strategies and the human population. Mycobacterium tuberculosis is a common causative agent responsible for increasing cases of TB and as reported by WHO, approximately, 1.5 million death occurred from TB in 2020. Identification of new therapies against drug-resistant TB is an urgent need to be considered primarily. The current investigation aims to find the potential biogenic chalcone against the potential targets of drug-resistant TB via in silico approach. The ligand library of biogenic chalcones was screened against DprE1. Results of molecular docking and in silico ADMET prediction revealed that ZINC000005158606 has lead-like properties against the targeted protein. Pharmacophore modeling was done to identify the pharmacophoric features and their geometric distance present in ZINC000005158606. The binding stability study performed using molecular dynamics (MD) simulation of the DprE1-ZINC000005158606 complex revealed the conformational stability of the complex system over 100 ns with minimum deviation. Further, the in silico anti-TB sensitivity of ZINC000005158606 was found to be higher as compared to the standards against Mycobacterium tuberculosis. The overall in silico investigation indicated the potential of identified hit to act as a lead molecule against Mycobacterium tuberculosis.

Polyhydroxyalkanoate synthesis by bacteria isolated from landfill and ETP with pomegranate peels as carbon source.

Many bacteria produce polyhydroxyalkanoates (PHAs) when exposed to stressful conditions. It is a known fact that PHAs have the potential to replace petrochemical-based plastics as they are biodegradable, biocompatible, and thermoprocessible materials. The study focusses on producing PHA from microbes isolated from polluted environments and pomegranate peels were utilized as a unique carbon source. This was done to ensure reduction in the cost of the substrate that has not yet been reported as a substrate for PHA production. A comparative study was also done with Cupriavidus necator, the reference strain. Out of many bacterial strains, isolated, eight of these were found to have ability to produce PHA. Pomegranate peel was substituted as carbon source in the medium and all bacterial isolates along with reference strain were used to test their ability to produce PHA from waste. Cupriavidus necator, the reference strain, yielded 71% PHA. Bacillus halotolerans DSM8802 yielded 83% at 1:1:: C:N ratio at 72 h.

Multimarker study of the effects of antifouling biocide on benthic organisms: results using Perna viridis as candidate species.

Toxic effects of continuous low dose application of the antifouling biocide chlorine on marine benthic organisms were monitored using transplanted green mussels (Perna viridis) and a suite of biomarkers. Caged mussels were deployed in chlorinated and non-chlorinated sections of the cooling system of an operating electric power plant. Biomarkers indicative of general stress, oxidative stress (superoxide dismutase and catalase), and DNA integrity, along with expression of stress proteins, were studied to assess the effects. Deterioration in condition index with corresponding increase in DNA strand breaks was indicative of chlorine stress. Superoxide dismutase enzyme did not show any particular trend, but catalase activity was high during the initial days of exposure at the chlorinated site; later, it became almost equal to that at the control site. Similarly, expressions of stress proteins (HSP60, HSP70, HSP22, GSTS1, and CYP4) showed bell-shaped pattern during the period of study. Positive correlation among the endpoints indicated the utility of the multimarker approach to monitor the effects of continuous low dose chlorination on mussels.

Comparative toxicological effects of two antifouling biocides on the marine diatom Chaetoceros lorenzianus: Damage and post-exposure recovery.

Antifouling biocides are commonly used in coastal electric power stations to prevent biofouling in their condenser cooling systems. However, the environmental impact of the chemical biocides is less understood than the thermal stress effects caused by the condenser effluents. In this study, Chaetoceros lorenzianus, a representative marine diatom, was used to analyse the toxicity of two antifouling biocides, chlorine and chlorine dioxide. The diatom cells were subjected to a range of concentrations of the biocides (from 0.05 to 2mg/L, as total residual oxidants, TRO) for contact time of 30min. They were analysed for viability, genotoxicity, chlorophyll a and cell density endpoints. The cells were affected at all concentrations of the biocides (0.05-2mg/L), showing dose-dependent decrease in viability and increase in DNA damage. The treated cells were later incubated in filtered seawater devoid of biocide to check for recovery. The cells were able to recover in terms of overall viability and DNA damage, when they had been initially treated with low concentrations of the biocides (0.5mg/L of Cl2 or 0.2mg/L of ClO2). Chlorophyll a analysis showed irreparable damage at all concentrations, while cell density showed increasing trend of reduction, if treated above 0.5mg/L of Cl2 and 0.2mg/L of ClO2. The data indicated that in C. lorenzianus, cumulative toxic effects and recovery potential of ClO2 up to 0.2mg/L were comparable with those of Cl2, up to 0.5mg/L concentration in terms of the studied endpoints. The results indicate that at the biocide levels currently being used at power stations, recovery of the organism is feasible upon return to ambient environment. Similar studies should be carried out on other planktonic and benthic organisms, which will be helpful in the formulation of future guidelines for discharge of upcoming antifouling biocides such as chlorine dioxide.

Chlorination-induced genotoxicity in the mussel Perna viridis: assessment by single cell gel electrophoresis (comet) assay.

Mussels are important fouling organisms in the cooling water systems of coastal power plants. Continuous low-dose chlorination (CLDC) is being practiced as an effective method to control mussel biofouling in power plant cooling water systems. CLDC effectively controls mussel fouling by discouraging larval settlement rather than by killing the larvae or adults. Mussels are an integral part of the natural benthic community in the receiving water body where the coolant water is discharged. Hence, from a toxicological point of view, they can serve as both target and non-target organisms. Previous researchers have indicated that chlorine residual, rather than elevated temperature, can be the major stress factor in the effluents released from coastal power plants. However, very little data are available on the sub-lethal effects of low level chlorination on representative benthic fauna. In this study, we used native and transplanted mussels (Perna viridis) to study lethal and sub-lethal effects of chlorination in the cooling water circuit of an operating power plant. Experiments involving comet assay suggested that CLDC can cause DNA damage in treated mussels. However, activation of DNA repair appeared to get initiated after the accrued damage reached a threshold. The results indicate that, at chlorine residual levels observed at the discharge point, exposure to chlorinated effluents is unlikely to cause significant genetic damage to mussels in the recipient water body.

Graphene quantum dots conjugated albumin nanoparticles for targeted drug delivery and imaging of pancreatic cancer.

Pancreatic cancer is considered to be the deadliest of all cancers due to its poor prognosis and resistance to conventional therapies. In this study, the potential of hyaluronic acid functionalized and green fluorescent graphene quantum dot (GQD)-labeled human serum albumin nanoparticles for pancreatic cancer specific drug delivery and bioimaging was explored. GQDs with tunable fluorescence properties and biocompatibility have attracted much more interest in recent years as compared to their metal semiconductor counterparts. We adopted lawsone (2-hydroxy-1,4-naphthoquinone) as a novel reducing agent for the synthesis of quantum dots and, in addition to excellent fluorescence of the synthesized GQDs, a good quantum yield of ∼14% was also obtained. Gemcitabine, the most preferred drug for pancreatic cancer treatment, was encapsulated in albumin nanoparticles, and it was observed that our nanoformulation significantly enhanced the bioavailability and sustained release property of the drug to pancreatic cancer cells in vitro. Moreover, the GQD-mediated bioimaging was excellent and enhanced the efficacy of our system as a drug delivery vehicle.