Correction: Siddhardha et al. Chrysin-Loaded Chitosan Nanoparticles Potentiates Antibiofilm Activity against Staphylococcus aureus. Pathogens 2020, 9, 115

The authors wish to make the following corrections to the original publication [...].

Ion-pumping microbial rhodopsin protein classification by machine learning approach

BACKGROUND

Rhodopsin is a seven-transmembrane protein covalently linked with retinal chromophore that absorbs photons for energy conversion and intracellular signaling in eukaryotes, bacteria, and archaea. Haloarchaeal rhodopsins are Type-I microbial rhodopsin that elicits various light-driven functions like proton pumping, chloride pumping and Phototaxis behaviour. The industrial application of Ion-pumping Haloarchaeal rhodopsins is limited by the lack of full-length rhodopsin sequence-based classifications, which play an important role in Ion-pumping activity. The well-studied Haloarchaeal rhodopsin is a proton-pumping bacteriorhodopsin that shows promising applications in optogenetics, biosensitized solar cells, security ink, data storage, artificial retinal implant and biohydrogen generation. As a result, a low-cost computational approach is required to identify Ion-pumping Haloarchaeal rhodopsin sequences and its subtype.

RESULTS

This study uses a support vector machine (SVM) technique to identify these ion-pumping Haloarchaeal rhodopsin proteins. The haloarchaeal ion pumping rhodopsins viz., bacteriorhodopsin, halorhodopsin, xanthorhodopsin, sensoryrhodopsin and marine prokaryotic Ion-pumping rhodopsins like actinorhodopsin, proteorhodopsin have been utilized to develop the methods that accurately identified the ion pumping haloarchaeal and other type I microbial rhodopsins. We achieved overall maximum accuracy of 97.78%, 97.84% and 97.60%, respectively, for amino acid composition, dipeptide composition and hybrid approach on tenfold cross validation using SVM. Predictive models for each class of rhodopsin performed equally well on an independent data set. In addition to this, similar results were achieved using another machine learning technique namely random forest. Simultaneously predictive models performed equally well during five-fold cross validation. Apart from this study, we also tested the own, blank, BLAST dataset and annotated whole-genome rhodopsin sequences of PWS haloarchaeal isolates in the developed methods. The developed web server ( https://bioinfo.imtech.res.in/servers/rhodopred ) can identify the Ion Pumping Haloarchaeal rhodopsin proteins and their subtypes. We expect this web tool would be useful for rhodopsin researchers.

CONCLUSION

The overall performance of the developed method results show that it accurately identifies the Ionpumping Haloarchaeal rhodopsin and their subtypes using known and unknown microbial rhodopsin sequences. We expect that this study would be useful for optogenetics, molecular biologists and rhodopsin researchers.

Anthropogenic impact accelerates antibiotic resistome diversity in the mangrove sediment of Indian Sundarban

Mangroves are situated in convergence zones between fresh and marine water and are prone to pollution and deforestation. This study explored the microbiome structure, function and antibiotic resistome of Indian Sundarban. The taxonomic Chao1 estimated diversity was highest in uninhabited Kalash (1204.64 ± 12.72) and lowest in Godkhali, which experiences considerable human activities (1158.76 ± 11.18). The alpha diversity showed negative correlation (p < 0.05) with PAH such as Acenaphthene (r = -0.56), Acenaphthylene (r = -0.62), Fluoranthene (r = -0.59), Fluorene (r = -0.55), Phenanthrene (r = -0.57), while the biochemical parameters phosphate (r = 0.58) and salinity (r = 0.58) had a significant (p < 0.05) positive correlation. The data suggest the importance of physicochemical parameters in maintaining the mangrove microbiome. The taxonomic composition was dominated by Proteobacteria (54.12 ± 0.37). All sites were dominated by ARGs such as rpoB2, cpxR, ompR, camP, and bacA. Comparing the Sundarban mangrove sediment resistome with mangrove from other sites in India (Kerala) and China (Guangxi, Hainan, and Shenzhen) suggested that resistome from Indian mangrove has a significantly (p < 0.05) higher ARG diversity compared to Chinese mangroves. Yet, the abundance of the ARG was significantly (p < 0.05) lower in the Indian mangroves posing a much greater risk if enriched. The study suggests that anthropogenic activities and pollution degrade the microbiome diversity, disturb the microbiome functions, and enrich ARGs.

Biosynthesis of Silver Chloride Nanoparticles (AgCl-NPs) from Extreme Halophiles and Evaluation of Their Biological Applications

The biosynthesis of nanoparticles (NPs) has gained an overwhelming interest due to their biological applications. However, NPs synthesis by pigmented extreme halophiles remains underexplored. The NPs synthesis using pigmented halophiles is inexpensive and less toxic than other processes. In this study, pigmented halophilic microorganisms (n = 77) were screened to synthesize silver chloride nanoparticles (AgCl-NPs) with silver nitrate as metal precursors, and their biological applications were assessed. The synthesis of AgCl-NPs was possible using the crude extract from cellular lysis (CECL) of six extreme halophiles. Two of the AgCl-NPs viz. AK2-NPs and MY6-NPs synthesized by the CECL of Haloferax alexandrinus RK_AK2 and Haloferax lucentense RK_MY6, respectively, exhibited antimicrobial, antioxidative, and anti-inflammatory activities. The surface plasmon resonance of the AgCl-NPs was determined with UV spectroscopy. XRD analysis of AK2-NPs and MY6-NPs confirmed the presence of silver in the form of chlorargyrite (silver chloride) having a cubic structure. The crystallite size of AK2-NPs and MY6-NPs, estimated with the Scherrer formula, was 115.81 nm and 137.50 nm. FTIR analysis verified the presence of diverse functional groups. Dynamic light-scattering analysis confirmed that the average size distribution of NPs was 71.02 nm and 117.36 nm for AK2-NPs and MY6-NPs, respectively, with monodisperse nature. The functional group in 1623-1641 cm^-1 indicated the presence of protein β-sheet structure and shifting of amino and hydroxyl groups from the pigmented CECL, which helps in capping and stabilizing nanoparticles. The study provides evidence that CECL of Haloferax species can rapidly synthesize NPs with unique characteristics and biological applications.

Attenuation of quorum sensing mediated virulence factors production and biofilm formation in Pseudomonas aeruginosa PAO1 by Colletotrichum gloeosporioides HM3

Signal dependent microbial communication in Pseudomonas aeruginosa PAO1 is a typical phenomenon mediated by acyl homo-serine lactone molecules that helps in developing biofilm and enhance antibiotic resistance. Microbial sources provide insight to the hidden treasure of secondary metabolites, and these structurally diversified chemical motifs can be used as antimicrobial and anti-infective agents. In the present study, endophytic fungus, Colletotrichum gloeosporioides HM3 isolated from Carica papaya leaves was explored for anti-infective potential against P. aeruginosa PAO1. The crude extract of C. gloeosporioides HM3 displayed bacteriostatic effect on P. aeruginosa PAO1 growth at 750 μg/ml concentration. A significant decline was observed in the production of quorum sensing regulated virulence factors, i.e. 56.32%, 62.54%, and 66.67% of pyocyanin, chitinase, and elastase enzyme, respectively. A drastic reduction in pathogenic determinant behaviour after treatment with crude extract of C. gloeosporioides HM3 i.e. EPS, rhamnolipid, and HCN production was noted. Light microscopy and CLSM analysis revealed that fungal extract treatment has reduced bacterial ability to form dense biofilm architecture. In silico analysis demonstrated the binding efficiency of bioactive compound, 4-(2,3-dimethoxybenzylidene)-3-methyl-1-(4-nitrophenyl)-2-pyrazolin-5-one, which is equipotent to the natural ligand and displayed a docking score of -5.436 kcal/mol with QS transcriptional regulator (LasR). Whereas the compound Acetamide, n-[tetrahydro-3-(phenylmethyl) thieno [3,4-d]thiazol-2 (3 h)-ylidene]-, s,s-dioxide exhibits a docking score of -4.088 kcal/mol (LasR) and -1.868 kcal/mol (RhlR) with cognate receptor proteins. Henceforth, the research report suggests C. gloeosporioides HM3 derived metabolites could be considered as a potential inhibitors of QS regulated virulence factors and biofilm production in P. aeruginosa PAO1.

Isolation and Taxonomic Characterization of Novel Haloarchaeal Isolates From Indian Solar Saltern: A Brief Review on Distribution of Bacteriorhodopsins and V-Type ATPases in Haloarchaea

Haloarchaea inhabit high salinity environments worldwide. They are a potentially rich source of crucial biomolecules like carotenoids and industrially useful proteins. However, diversity in haloarchaea present in Indian high salinity environments is poorly studied. In the present study, we isolated 12 haloarchaeal strains from hypersaline Kottakuppam, Tamil Nadu solar saltern in India. 16S rRNA based taxonomic characterization of these isolates suggested that nine of them are novel strains that belong to genera Haloarcula, Halomicrobium, and Haloferax. Transmission electron microscopy suggests the polymorphic nature of these haloarchaeal isolates. Most of the haloarchaeal species are known to be high producers of carotenoids. We were able to isolate carotenoids from all these 12 isolates. The UV-Vis spectroscopy-based analysis suggests that bacterioruberin and lycopene are the major carotenoids produced by these isolates. Based on the visual inspection of the purified carotenoids, the isolates were classified into two broad categories i.e., yellow and orange, attributed to the differences in the ratio of bacterioruberin and lycopene as confirmed by the UV-Vis spectral analysis. Using a PCR-based screening assay, we were able to detect the presence of the bacteriorhodopsin gene (bop) in 11 isolates. We performed whole-genome sequencing for three bop positive and one bop negative haloarchaeal isolates. Whole-genome sequencing, followed by pan-genome analysis identified multiple unique genes involved in various biological functions. We also successfully cloned, expressed, and purified functional recombinant bacteriorhodopsin (BR) from one of the isolates using Escherichia coli as an expression host. BR has light-driven proton pumping activity resulting in the proton gradient across the membrane, which is utilized by V-Type ATPases to produce ATP. We analyzed the distribution of bop and other accessory genes involved in functional BR expression and ATP synthesis in all the representative haloarchaeal species. Our bioinformatics-based analysis of all the sequenced members of genus Haloarcula suggests that bop, if present, is usually inserted between the genes coding for B and D subunits of the V-type ATPases operon. This study provides new insights into the genomic variations in haloarchaea and reports expression of new BR variant having good expression in functional form in E. coli.

16s rRNA metagenomic analysis reveals predominance of Crtl and CruF genes in Arabian Sea coast of India

Microbial communities perform crucial biogeochemical cycles in distinct ecosystems. Halophilic microbial communities are enriched in the saline areas. Hence, haloarchaea have been primarily studied in salterns and marine biosystems with the aim to harness haloarcheal carotenoids biosynthesis. In this study, sediment from several distinct biosystems (mangrove, seashore, estuary, river, lake, salt pan and island) across the Arabian coastal region of India were collected and analyzed though 16s rRNA metagenomic and whole genome approach to elucidated the dominant representative genre, haloarcheal diversity, and the prevalence of Crtl and CruF genes. We found that the microbial diversity in mangrove sediment (794 OTUs) was highest and lowest in lake and river (558-560 OTUs). Moreover, the bacterial domain dominated in all biosystems (96.00-99.45%). Top 10 abundant genera were involved in biochemical cycles such as sulfur, methane, ammonia, hydrocarbon degradation, and antibiotics production. The Archaea was mainly composed of Haloarchaea, Methanobacteria, Methanococci, Methanomicrobia and Crenarchaeota. Carotenoid gene, Crtl, was observed in a major portion (abundance 60%; diversity 45%) of microbial community. Interestingly, we found that all species under haloarcheal class that were represented in fresh as well as marine biosystems encodes CruF gene (bacterioruberin carotenoid). Our study demonstrates the high microbial diversity in various ecosystems, enrichment of Crtl gene, and also shows that Crtl and CruF genes are highly abundant in haloarcheal genera. The finding of ecosystems specific Crtl and CruF encoding genera opens up a promising area in bioprospecting the carotenoid derivatives from the wide range of natural biosystems.

Novel Nanotherapeutics as Next-generation Anti-infective Agents: Current Trends and Future Prospectives

With the ever-increasing population and improvement in the healthcare system in the 21st century, the incidence of chronic microbial infections and associated health disorders has also increased at a striking pace. The ability of pathogenic microorganisms to form biofilm matrix aggravates the situation due to antibiotic resistance phenomenon resulting in resistance against conventional antibiotic therapy which has become a public health concern. The canonical Quorum Sensing (QS) signaling system hierarchically regulates the expression of an array of virulence phenotypes and controls the development of biofilm dynamics. It is imperative to develop an alternative, yet effective and non-conventional therapeutic approach, popularly known as "anti-infective therapy" which seems to be interesting. In this regard, targeting microbial QS associated virulence and biofilm development proves to be a quite astonishing approach in counteracting the paucity of traditional antibiotics. A number of synthetic and natural compounds are exploited for their efficacy in combating QS associated microbial infections but the bioavailability and biocompatibility limit their widespread applications. In this context, the nanotechnological intervention offers a new paradigm for widespread biomedical applications starting from targeted drug delivery to diagnostics for the diagnosis and treatment of infectious diseases, particularly to fight against microbial infections and antibiotics resistance in biofilms. A wide range of nanomaterials ranging from metallic nanoparticles to polymeric nanoparticles and recent advances in the development of carbon-based nanomaterials such as Carbon Nanotubes (CNTs), Graphene Oxide (GO) also immensely exhibited intrinsic antiinfective properties when targeted towards microbial infections and associated MDR phenomenon. In addition, the use of nano-based platforms as carriers emphatically increases the efficacy of targeted and sitespecific delivery of potential drug candidates for preventing microbial infections.

Inhibition of Microbial Quorum Sensing Mediated Virulence Factors by Pestalotiopsis sydowiana

Quorum sensing (QS)-mediated infections cause severe diseases in human beings. The control of infectious diseases by inhibiting QS using antipathogenic drugs is a promising approach as antibiotics are proving inefficient in treating these diseases. Marine fungal (Pestalotiopsis sydowiana PPR) extract was found to possess effective antipathogenic characteristics. The minimum inhibitory concentration (MIC) of the fungal extract against test pathogen Pseudomonas aeruginosa PAO1 was 1,000 μg/ml. Sub-MIC concentrations (250 and 500 μg/ml) of fungal extract reduced QS-regulated virulence phenotypes such as the production of pyocyanin, chitinase, protease, elastase, and staphylolytic activity in P. aeruginosa PAO1 by 84.15%, 73.15%, 67.37%, 62.37%, and 33.65%, respectively. Moreover, it also reduced the production of exopolysaccharides (74.99%), rhamnolipids (68.01%), and alginate (54.98%), and inhibited the biofilm formation of the bacteria by 90.54%. In silico analysis revealed that the metabolite of P. sydowiana PPR binds to the bacterial QS receptor proteins (LasR and RhlR) similar to their respective natural signaling molecules. Cyclo(-Leu-Pro) (CLP) and 4-Hydroxyphenylacetamide (4-HPA) were identified as potent bioactive compounds among the metabolites of P. sydowiana PPR using in silico approaches. The MIC values of CLP and 4-HPA against P. aeruginosa PAO1 were determined as 250 and 125 μg/ml, respectively. All the antivirulence assays were conducted at sub-MIC concentrations of CLP (125 μg/ml) and 4-HPA (62.5 μg/ml), which resulted in marked reduction in all the investigated virulence factors. This was further supported by gene expression studies. The findings suggest that the metabolites of P. sydowiana PPR can be employed as promising QS inhibitors that target pathogenic bacteria.

Chrysin-Loaded Chitosan Nanoparticles Potentiates Antibiofilm Activity against Staphylococcus aureus

The application of nanotechnology in medicine is gaining popularity due to its ability to increase the bioavailability and biosorption of numerous drugs. Chrysin, a flavone constituent of Orocylumineicum vent is well-reported for its biological properties. However, its therapeutic potential has not been fully exploited due to its poor solubility and bioavailability. In the present study, chrysin was encapsulated into chitosan nanoparticles using TPP as a linker. The nanoparticles were characterized and investigated for their anti-biofilm activity against Staphylococcus aureus. At sub-Minimum Inhibitory Concentration, the nanoparticles exhibited enhanced anti-biofilm efficacy against S. aureus as compared to its bulk counterparts, chrysin and chitosan. The decrease in the cell surface hydrophobicity and exopolysaccharide production indicated the inhibitory effect of the nanoparticles on the initial stages of biofilm development. The growth curve analysis revealed that at a sub-MIC, the nanoparticles did not exert a bactericidal effect against S. aureus. The findings indicated the anti-biofilm activity of the chrysin-loaded chitosan nanoparticles and their potential application in combating infections associated with S. aureus.

Antimicrobial photodynamic therapy on Staphylococcus aureus and Escherichia coli using malachite green encapsulated mesoporous silica nanoparticles: an in vitro study

Background

Rise in the number of healthcare associated or hospital acquired infections is a major problem affecting the global healthcare sector. We evaluated superior antibacterial and antibiofilm photodynamic therapy (aPDT) using malachite green encapsulated mesoporous silica nanoparticles (MG-MSN) against Staphylococcus aureus and Escherichia coli, which are known to be major causative agents of nosocomial infections.

Methods

Malachite green (MG) was encapsulated on mesoporous silica nanoparticles (MSN). Fourier-transform infrared spectroscopy, Transmission electron microscopy, and spectroscopic analysis were performed to characterize the MG-MSN. The antimicrobial efficacies of MSN, MG, and MG-MSN were investigated and the results were recorded.

Results

MG-MSN was effective against both the tested bacteria. S. aureus was more phototoxic to MG-MSN compared to E. coli. The antibiofilm efficacy of MG-MSN on E. coli and S. aureus was also studied. Biofilm inhibition was 65.68 ± 2.62% in E. coli and 79.66 ± 3.82% in S. aureus. Cell viability assay, exopolysaccharides quantification, and confocal laser scanning microscopy studies also revealed the enhanced antibiofilm activity of MG-MSN when used as a potential photosensitizer for aPDT. This study can be extended to eradicate these strains from localized superficial infections and medical appliances, preventing nosocomial infections.

Malachite green-conjugated multi-walled carbon nanotubes potentiate antimicrobial photodynamic inactivation of planktonic cells and biofilms of Pseudomonas aeruginosa and Staphylococcus aureus

Purpose: Infections associated with medical devices that are caused by biofilms remain a considerable challenge for health care systems owing to their multidrug resistance patterns. Biofilms of Pseudomonas aeruginosa and Staphylococcus aureus can result in life-threatening situations which are tough to eliminate by traditional methods. Antimicrobial photodynamic inactivation (aPDT) constitutes an alternative method of killing deadly pathogens and their biofilms using reactive oxygen species (ROS). This study investigated the efficacy of enhanced in vitro aPDT of P. aeruginosa and S. aureus using malachite green conjugated to carboxyl-functionalized multi-walled carbon nanotubes (MGCNT). Both the planktonic cells and biofilms of test bacteria were demonstrated to be susceptible to the MGCNT conjugate. These MGCNT conjugates may thus be employed as a facile strategy for designing antibacterial and anti-biofilm coatings to prevent the infections associated with medical devices. Methods: Conjugation of the cationic dye malachite green to carbon nanotube was studied by UV-visible spectroscopy, high-resolution transmission electron microscopy, and Fourier transform infrared spectrometry. P. aeruginosa and S. aureus photodestruction were studied using MGCNT conjugate irradiated for 3 mins with a red laser of wavelength 660 nm and radiant exposure of 58.49 J cm^-2. Results: Upon MGCNT treatment, S. aureus and P. aeruginosa were reduced by 5.16 and 5.55 log₁₀ , respectively. Compared to free dye, treatment with MGCNT afforded improved phototoxicity against test bacteria, concomitant with greater ROS production. The results revealed improved biofilm inhibition, exopolysaccharide inhibition, and reduced cell viability in test bacteria treated with MGCNT conjugate. P. aeruginosa and S. aureus biofilms were considerably reduced to 60.20±2.48% and 67.59±3.53%, respectively. Enhanced relative MGCNT phototoxicity in test bacteria was confirmed using confocal laser scanning microscopy. Conclusion: The findings indicated that MGCNT conjugate could be useful to eliminate the biofilms formed on medical devices by S. aureus and P. aeruginosa.

ANTI QUORUM SENSING AND ANTI BIOFILM POTENTIAL OF ANOGEISSUS ACUMINATA AND MALLOTUS ROXBURGHIANUS MUELL. AGAINST PSEUDOMONAS AERUGINOSA PAO1

Pseudomonas aeruginosa causes severe persistent infections in immunocompromised patients by showing tolerance conventional antibiotic therapy by virtue of specialized hierarchy of quorum sensing (QS) network. The purpose of the study was to evaluate the efficacy of two Mizoram medicinal plants i.e., Anogeissus acuminata and Mallotus roxburghianus Muell. in attenuating QS regulated P. aeruginosa virulence. The crude leaf extracts were tested for their ability to combat QS associated virulence phenotypes such as pyocyanin production, LasB elastase and Staphylolytic activity and production of biofilm determinants such as alginate and exopolysaccharide in P. aeruginosa PAO1. The gas chromatography mass spectrometry (GC-MS) analysis revealed the presence of phytocompounds, the synergistic activity of which is responsible for the anti QS activity. The in silico studies provide the binding efficacy of obtained phytochemical with QS receptor protein, LasR. The in vitro studies followed by in silico analysis demonstrated the efficacy of phytochemical of A. acuminata and M. roxburghianus Muell. in competitively inhibiting the binding of natural ligand with LasR and thereby altering production of virulence phenotypes. The efficacy in down regulating bacterial virulence shown by A. acuminata and M. roxburghianus Muell. provides promising alternatives to develop next generation anti-pathogenic agents.

Antimicrobial photodynamic activity of toluidine blue encapsulated in mesoporous silica nanoparticles against Pseudomonas aeruginosa and Staphylococcus aureus

In the present study, the antimicrobial and antibiofilm efficacy of toluidine blue (TB) encapsulated in mesoporous silica nanoparticles (MSN) was investigated against Pseudomonas aeruginosa and Staphylococcus aureus treated with antimicrobial photodynamic therapy (aPDT) using a red diode laser 670 nm wavelength, 97.65 J cm^-2 radiant exposure, 5 min). Physico-chemical techniques (UV-visible (UV-vis) absorption, photoluminescence emission, excitation, and FTIR) and high-resolution transmission electron microscopy (HR-TEM) were employed to characterize the conjugate of TB encapsulated in MSN (TB MSN). TB MSN showed maximum antimicrobial activities corresponding to 5.03 and 5.56 log CFU ml^-1 reductions against P. aeruginosa and S. aureus, respectively, whereas samples treated with TB alone showed 2.36 and 2.66 log CFU ml^-1 reductions. Anti-biofilm studies confirmed that TB MSN effectively inhibits biofilm formation and production of extracellular polymeric substances by P. aeruginosa and S. aureus.

Determination of antioxidant potential of Acacia nilotica leaf extract in oxidative stress response system of Saccharomyces cerevisiae

BACKGROUND

From ancient times, plants and plant-derived products have been used as folkloric medicines for a variety of health disorders owing to their tremendous therapeutic potential. The present study aimed to determine the antioxidant efficacy of crude Acacia nilotica extract in the oxidative stress response system of Saccharomyces cerevisiae as a model organism.

RESULTS

Acacia nilotica showed significant antioxidant activity, with IC₅₀ values of 75.157 and 159.57 µg mL^-1 for 2,2-diphenyl-1-picrylhydrazyl radical and hydroxyl radical scavenging activities respectively at a concentration of 500 µg mL^-1 . The total antioxidant activity of A. nilotica showed an ascorbic acid equivalent of 152.79 ± 7.43 µg mL^-1 . The presence of phytoconstituents such as phytol and α-tocopherol from gas chromatography/mass spectrometry analysis confirmed the potential of A. nilotica as an antioxidant. The results were validated using the stress response mechanism in S. cerevisiae wild type and its isogenic deletion strains sod1Δ and tsa1Δ. Acacia nilotica substantially neutralized reactive oxygen species generated by hydrogen peroxide in mutant strains, as evident from spot assay and fluorescence assay using fluorescence microscopy and intensity studies.

CONCLUSION

The results suggested the efficacy of A. nilotica as a potent antioxidant in the S. cerevisiae system for the first time and its use in neutraceuticals/therapeutics. © 2017 Society of Chemical Industry.

Elucidation of photocatalysis, photoluminescence and antibacterial studies of ZnO thin films by spin coating method

The ZnO thin films have been prepared by spin coating followed by annealing at different temperatures like 300°C, 350°C, 400°C, 450°C, 500°C & 550°C and ZnO nanoparticles have been used for photocatalytic and antibacterial applications. The morphological investigation and phase analysis of synthesized thin films well characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Photoluminescence (PL), Transmission Electron Microscopy (TEM) and Raman studies. The luminescence peaks detected in the noticeable region between 350nm to 550nm for all synthesized nanosamples are associated to the existence of defects of oxygen sites. The luminescence emission bands are observed at 487nm (blue emission), and 530nm (green emission) at the RT. It is observed that there are no modification positions of PL peaks in all ZnO nanoparticles. In the current attempt, the synthesized ZnO particles have been used photocatalytic and antibacterial applications. The antibacterial activity of characterized samples was regulated using different concentrations of synthesized ZnO particles (100μg/ml, 200μg/ml, 300μg/ml, 400μg/ml, 500μg/ml and 600μg/ml) against gram positive and gram negative bacteria (S. pnemoniae, S. aureus, E. coli and E. hermannii) using agar well diffusion assay. The increase in concentration, decrease in zone of inhibition. The prepared ZnO morphologies showed photocatalytic activity under the sunlight enhancing the degradation rate of Rhodamine-B (RhB), which is one of the common water pollutant released by textile and paper industries.

Determination of antioxidant activity of Hibiscus sabdariffa and Croton caudatus in Saccharomyces cerevisiae model system

From ancient times, plants and plant derived products are exploited as a prominent source of folkloric medicines with tremendous therapeutic potential for an array of health disorders. In the present study, ethanolic leaf extract of Hibiscus sabdariffa and Croton caudatus were evaluated for free radical scavenging activity in Saccharomyces cerevisiae model system. H. sabdariffa and C. caudatus showed tremendous DPPH free radical scavenging potential with an IC₅₀ value of 184.88 and 305.39 µg/mL respectively at a concentration of 500 µg/mL. The ethanolic leaf extract of H. sabdariffa and C. caudatus also showed significant hydoxyl radical scavenging and total antioxidant activity. Ascorbic acid was used as positive control. The in vitro antioxidant activity was further supported by in vivo studies using radical scavenging mechanism in S. cerevisiae wild type and its isogenic deletion strains sod1∆ and tsa1∆. The mutant yeast cells substantially scavenged the stress generated by H₂O₂ when supplemented with ethanolic leaf extract of H. sabdariffa and C. caudatus as evident from spot assays followed by fluorescence assay (DCF-DA) using fluorescence microscopic and intensity studies. H. sabdariffa and C.caudatus significantly neutralize the ROS level in yeast mutants with concomitant decrease in fluorescence intensity as compared to the untreated yeast cells. The results suggested the efficacy of H. sabdariffa and C. caudatus as potent antioxidants in yeast system and thus their futuristic applications in therapeutics.

Biotransformation of α-Pinene to Terpineol by Resting Cell Suspension of Absidia corulea

Microbial biotransformation of monoterpenes results in the formation of many valuable compounds. Many microorganisms can be used to carry out extremely specific conversions using substrates of low commercial value. Absidia corulea MTCC 1335 was examined for its ability to transform α-Pinene enantiomers. The substrates (-)-α-Pinene and (+)-α-Pinene converted to α-terpineol and isoterpineol, were detected in gas chromatographic analysis. The Biotransformation kinetics of the oxidized products were analysed using GC-MS. With both the substrates the products formed were similar and not much difference in the rate of transformation was observed, suggesting no enantioselectivity of organism towards the substrate.

Isolation, Characterization and Biological evaluation of secondary metabolite from Aspergillus funiculosus

Screening of Aspergillus funiculosus for bioactive secondary metabolites produced kojic acid, which is know to have wide range of biological properties. It is very active against Gram-negative bacteria, such as Pseudomonas aeruginosa and Escherichia coli, but moderately active against yeasts and Gram-positive bacteria except Staphylococcus epidermidis. Filamentous Fungi are more sensitive to kojic acid. When it exposed to larvicidal activity on Aedes aegypti third instar larvae are more sensitive than early fourth instar larvae.

Anti-tubercular agents. Part IV: Synthesis and antimycobacterial evaluation of nitroheterocyclic-based 1,2,4-benzothiadiazines

In continuation of our earlier work on benzothiadiazines, we have prepared a series of nitrofuran, nitrothiophene and arylfuran coupled benzothiadiazines and evaluated them for antimycobacterial and antibacterial activities. One of the compounds 2f has shown good in vitro antimycobacterial activity. All the synthesized compounds have shown moderate to good antibacterial activity.