S. Vignesh

Antibiotic resistant pathogens versus human impacts: A study from three eco-regions of the Chennai coast, southern India

We assessed the occurrence of pollution indicators and antibiotic resistant bacterial isolates from water and sediment samples of three different eco-regions of the Chennai coast between March - May of 2010. Total of 960 bacterial strains belonging to four genera were isolated which show the highest frequencies of resistance to vancomycin (53.6%) and penicillin (52.6%) (except Enterococcus sp., which is highly resistant to erythromycin) and lowest frequencies of resistance to chloramphenicol (3.43%), ciprofloxacin (3.95%), gentamicin (4.68%), and tetracycline (6.97%). The E. coli, Vibrio sp., Salmonella sp. and Enterococcus sp. show high frequency of resistance to 2-5 antibacterials of 60.4%, 45.83%, 69.16% and 46.6%, respectively. High pollution indices (PI - 6.66-14.06) and antibiotic resistance indices (ARI - 0.29-0.343) indicate that the coastal environment is highly exposed to antibiotic sources that suggesting to avoid direct contact.

Synthesis and concentration dependent antibacterial activities of CuO nanoflakes

We report, synthesis and antibacterial activities of CuO nanoflakes. CuO nanoparticles are prepared at room temperature through sol-gel method. X-ray diffraction studies show the particles are monoclinic (crystalline) in nature. Scanning electron microscopy (SEM) images clearly show that the prepared particles are flake like in structure. Fourier transform infrared (FTIR) spectra exhibits three different bands that correspond to the Au and Bu modes. Antibacterial studies were performed on Shigella flexneri, Staphylococcus aureus, Staphylococcus epidermidis, Salmonella typhimurium, Bacillus subtilis, Escherichia coli, Vibrio cholera, Pseudomonas aeruginosa and Aeromonas liquefaciens bacterial strains. Among these bacterial strains, S. flexneri and B. subtilis are most sensitive to copper oxide nanoparticles than the positive control (Penicillin G) and S. typhimurium strain shows the less sensitive. Results show that sensitivity is highly dependent on the concentrations of CuO nanoflakes.

DNA/RNA binding and anticancer/antimicrobial activities of polymer-copper(II) complexes.

Water soluble polymer-copper(II) complexes with various degrees of coordination in the polymer chain were synthesized and characterized by elemental analysis, IR, UV-visible and EPR spectra. The DNA/RNA binding behavior of these polymer-copper(II) complexes was examined by UV-visible absorption, emission and circular dichroism spectroscopic methods, and cyclic voltammetry techniques. The binding of the polymer-copper(II) complexes with DNA/RNA was mainly through intercalation but some amount of electrostatic interaction was also observed. This binding capacity increased with the degree of coordination of the complexes. The polymer-copper(II) complex having the highest degree of coordination was subjected to analysis of cytotoxic and antimicrobial properties. The cytotoxicity study indicated that the polymer-copper(II) complexes affected the viability of MCF-7 mammary carcinoma cells, and the cells responded to the treatment with mostly through apoptosis although a few cells succumbed to necrosis. The antimicrobial screening showed activity against some human pathogens.

A comparative study on the binding of single and double chain surfactant-cobalt(III) complexes with bovine serum albumin.

The comparative binding effect of single and double aliphatic chain containing surfactant-cobalt(III) complexes cis-[Co(bpy)2(DA)2](ClO4)3·2H2O (1), cis-[Co(bpy)2(DA)Cl](ClO4)2·2H2O (2), cis-[Co(phen)2(CA)2](ClO4)3·2H2O (3), and cis-[Co(phen)2(CA)Cl](ClO4)2·2H2O (4) with bovine serum albumin (BSA) under physiological condition was analyzed by steady state, time resolved fluorescence, synchronous, three-dimensional fluorescence, UV-Visible absorption and circular dichroism spectroscopic techniques. The results show that these complexes cause the fluorescence quenching of BSA through a static mechanism. The binding constants (Kb) and the number of binding sites were calculated and binding constant values are found in the range of 10(4)-10(5) M(-1). The results indicate that compared to single chain complex, double chain surfactant-cobalt(III) complex interacts strongly with BSA. Also the sign of thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicate that all the complexes interact with BSA through hydrophobic force. The binding distance (r) between complexes and BSA was calculated using Förster non-radiation energy transfer theory and found to be less than 7 nm. The results of synchronous, three dimensional fluorescence and circular dichroism spectroscopic methods indicate that the double chain surfactant-cobalt(III) complexes changed the conformation of the protein considerably than the respective single chain surfactant-cobalt(III) complexes. Antimicrobial studies of the complexes showed good activities against pathogenic microorganisms.

Synthesis and Antifungal Studies on CuO Nanostructures

We report, synthesis and antifungal activities of CuO nanoparticles. Particles are prepared through sol-gel method. X-ray diffraction studies show the particles are monoclinic (crystalline) in nature. Scanning electron microscopic measurements are carried out to understand the morphology of the prepared particles. Energy-dispersive X-ray spectroscopic measurements show that the prepared particles containing Cu and O. To identify the local structure of the particles Fourier transform infra red (FTIR) spectroscopic measurements were carried out showing vibrational bands of Cu-O and O-H band. Anti fungal studies were performed on the set of fungal using disk diffusion method and found that the prepared particles are suitable for antifungal activities.

Microbial Pollution Indicators in the Cauvery River, Southern India

The River Cauvery is one of the largest rivers of the Indian subcontinent. It originates from the Brahmagiri range of the Western Ghats, and flows for about 800 km west to east before debauching at the Bay of Bengal. Because of its importance in the Indian culture and dense population residing at its banks, it faces several forced and unforced human activities. This river system of Tamilnadu was studied in detail for the present status of water quality. Water samples were collected from 17 different sites from the Krishnarajasager reservoir up to the estuarine regions. Microbiological analysis was performed during four seasons (2010). Measured parameters include, bacterial analysis; total viable count (TVC), total coliform count (TC), total streptococci count (TS) and six different types of pathogenic bacteria. It is inferred from the study that the total coliforms (TC) were in the magnitude of 103 ml−1 for most of the sites, - higher than the permissible limits. The pollution indices (PI) ratio were high in all the seasons and maximum was observed in urban (S6 – 12.5) areas. The monsoon season showed the presence of higher levels of bacterial pollution than other seasons.

ANTIFUNGAL STUDIES ON BIOCOMPATIBLE POLYMER ENCAPSULATED SILVER NANOPARTICLES

Silver nanoparticles are known to have inhibitory antimicrobial properties. In this letter, we report the synthesis of silver nanoparticles by using biocompatible, water soluble polymer through polyol method. Optical absorption spectrum of the prepared particles shows an absorption peak around 433 nm which is because of Surface Plasmon Resonance (SPR) of silver nanoparticles. Fourier transform infrared (FTIR) studies were done to identify the interaction of the nanoparticle and polymer. Transmission Electron Microscopic (TEM) studies confirm that the prepared particles are ~ 100 nm in size. Antifungal activity was studied through standard disk diffusion method. Studies show the prepared particles are potential candidates for the antifungal activity.

Biomonitoring along the Tropical Southern Indian Coast with Multiple Biomarkers

We assessed the spatial and temporal variations of pollution indicators and geochemical and trace metal parameters (23 in total) from water and sediment (144 samples) of three different eco-niches (beach, fishing harbor, and estuary) in larger coastal cities of southern India (Cuddalore and Pondicherry) for one year. A total of 120 marine Pseudomonas isolates were challenged against different concentrations of copper solutions and 10 different antibiotics in heavy metal and antibiotic resistance approaches, respectively. The study shows that 4.16% of the isolates could survive in 250 mM of copper; 70% were resistant to minimum concentrations. Strains were resistant (98.4%) to at least one antibiotic in Cuddalore compared to the Pondicherry (78.4%) region. Pollution index (PI) (0–14.55) and antibiotic resistance index (ARI) (0.05–0.10) ratio indicated that high bacterial and antibiotic loads were released into the coastal environment. The degree of trace metal contamination in sediments were calculated by enrichment factor (EF), contamination factor (CF), pollution load index (PLI), and geo-accumulation index (Igeo). Statistical parameters like two-way analysis of variance (ANOVA), correlation, factor analysis and scatter matrix tools were employed between the 23 parameters in order to find sources, pathways, disparities and interactions of environmental pollutants. It indicates that geochemical and biological parameters were not strongly associated with each other (except a few) and were affected by different sources. Factor analysis elucidated, ‘microbe–metal’ interaction (Factor 1–48.86%), ‘anthropogenic’ factor (Factor 2–13.23%) and ‘Pseudomonas–Cadmium’ factor (Factor 3–11.74%), respectively.

Marine Drugs Development and Social Implication

Marine sources have attracted much attention as potential sources for natural products over recent years. The future of the biopharmaceutical holds great promise due to the many compounds that have and will be isolated from marine sources. Marine organisms have long been recognized as a source of novel metabolites with applications in human disease therapy. The marine environment is a rich source of both biological and chemical diversity, where it has been reported that oceans contain nearly 300,000 described species, representing only a small percentage of the total number of species that have to be discovered. The ocean represents a rich resource for ever more novel compounds with great potential as pharmaceutical, nutritional supplements, cosmetics, agrichemicals and enzymes, where each of these marine bioproducts has a strong potential market value. The reasons for the strong showing of drug discovery from natural products can be attributed to the diverse structures, intricate carbon skeletons, and the ease that human bodies will accept these molecules with minimal manipulation. With new pressures from the public and governments around the world to develop products to combat diseases and infections commonly encountered, new chemical entities need to be found and developed.