Arumugam Sundaramanickam

Biosynthesis of silver nanoparticles from the marine seaweed Sargassum wightii and their antibacterial activity against some human pathogens

In this paper, we have reported on biological synthesis of nano-sized silver and its antibacterial activity against human pathogens. The nanoparticles of silver were formed by the reduction of silver nitrate to aqueous silver metal ions during exposure to the extract of marine seaweed Sargassum wightii. The optical properties of the obtained silver nanoparticles were characterized using UV–visible absorption and room temperature photoluminescence. The X-ray diffraction results reveal that the synthesized silver nanoparticles are in the cubic phase. The existence of functional groups was identified using Fourier transform infrared spectroscopy. The morphology and size of the synthesized particles were studied with atomic force microscope and high-resolution transmission electron microscope measurements. The synthesized nanoparticles have an effective antibacterial activity against S. aureus, K. pneumoniae, and S. typhi.

Biosurfactant Producing Microbes and their Potential Applications: A Review

Biosurfactants are surface-active biomolecules produced by microbes (bacteria, fungi, and yeast) and have several advantages over the chemical surfactants, such as lower toxicity, higher biodegradability, better environmental compatibility, higher foaming, high selectivity, and specific activity under extreme conditions such as temperature, pH, and salinity. Almost all the surfactants now available in the market are chemically synthesized. Recently, attention toward the biosurfactants was doubled, which is mainly due to their wide range of functional properties and the diverse synthetic capabilities of the microbes. Microbial biosurfactants are found to have a wide range of applications in environmental protection, which include enhancing oil recovery, controlling oil spills, biodegradation, and detoxification of oil-contaminated industrial effluents and soils. Biosurfactants produced by microorganisms have potential applications in pharmaceutical/medicine, food, cosmetic, pesticide, oil, and biodegradation industries. In this review article, we concentrated on three important aspects such as various types of biosurfactants, the group of microbes involved in the production of biosurfactants, and application of microbial biosurfactants.

Distribution and Seasonal Variation of Heavy Metals in Sediments of Muthupet Lagoon, Southeast Coast of India

This study deals with seasonal variation of heavy metals in sediments of Muthupet lagoon, Southeast coast of India from September 2011 to August 2012. The bulk sediments were association with sand, silt and clay. Geo-accumulation index (lgeo) was used to quantitatively assess the influences of heavy metal pollution. Heavy metals were determined by using Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) and the results were compared to permissible limits of WHO/USEPA. The minimum concentration of heavy metals in all the stations were found during the post monsoon and summer seasons and the maximum concentration of heavy metals in all the stations were found during the pre-monsoon and monsoon seasons. The reason for the pollution was land drainage, irrigation through channels and municipal wastes and also the peak agricultural activities due to the release of fresh water from reservoirs. Among all the metals iron was found to be maximum in all the stations in post-monsoon and summer season followed by magnesium and manganese. Apart from these three metal, all other six metals are recorded in moderate range. The reason for the high concentration of these metals are anthropogenic activity, agriculture, aquaculture and the rivers regular in and out flow throughout the study duration in the lagoon area.

In vitro anticancer activity of silver nanoparticle synthesized by Escherichia coli VM1 isolated from marine sediments of Ennore southeast coast of India

In the present investigation, the bacterium Escherichia coli (VM1) was isolated from a marine sediments of Ennore coastal water along southeast coast of India was exploited for its capability of Ag NPs synthesis. The derived nanoparticles were characterized employing ultraviolet-visible (UV-vis) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, X-ray diffraction and High Resolution Transmission Electron Microscopy (HRTEM) studies. The Ag NPs were further subjected to MTT assay to evaluate their anticancer activity against human lung cancer cell line (A549), human cervical cancer cell line (HeLa) and normal (Vero) cell line. The marine E. coli (VM1) synthesized silver nanoparticles exhibited considerable cytotoxic influence against human cancer cell lines, thereby suggesting that they have tremendous potential as effective anticancer agents.

Bioremediation of Mercury by Vibrio fluvialis Screened from Industrial Effluents

Thirty-one mercury-resistant bacterial strains were isolated from the effluent discharge sites of the SIPCOT industrial area. Among them, only one strain (CASKS5) was selected for further investigation due to its high minimum inhibitory concentration of mercury and low antibiotic susceptibility. In accordance with 16S ribosomal RNA gene sequences, the strain CASKS5 was identified as Vibrio fluvialis. The mercury-removal capacity of V. fluvialis was analyzed at four different concentrations (100, 150, 200, and 250 μg/ml). Efficient bioremediation was observed at a level of 250 μg/ml with the removal of 60% of mercury ions. The interesting outcome of this study was that the strain V. fluvialis had a high bioremediation efficiency but had a low antibiotic resistance. Hence, V. fluvialis could be successfully used as a strain for the ecofriendly removal of mercury.

Biosorption of multi-heavy metals by coral associated phosphate solubilising bacteria Cronobacter muytjensii KSCAS2

This paper examines the potential detoxification efficiency of heavy metals by phosphate solubilising bacteria (PSB) that were isolated from coral, sea grass and mangrove environment. Initially, four potential bacterial isolates were selected based on their phosphate solubilisation index from 42 strains and were used for the metal tolerance test. Among the four isolates, KSCAS2 exhibited maximum tolerance to heavy metals and the phenotype indicated the production of extra polymeric substances. In a multi-heavy metal experimental setup at two concentrations (100 and 200 mg L-l), it has been demonstrated that the bacteria have extracellularly sequestered metal ions in amorphous deposits and this has been confirmed by scanning electron microscopy. In experiments with a 100 mg L-1 initial metal concentration, the percentages of metal removal by bacteria were 55.23% of Cd, 72.45% of Cr, 76.51% of Cu and 61.51% of Zn, respectively. In subsequent experiments, when the metal concentration was increased up to 200 mg L-l, the metal removal capacity decreased as follows: 44.62%, 63.1%, 67% and 52.80% for Cd, Cr, Cu and Zn, respectively. In addition, the biosorption of heavy metals was confirmed by the Fourier transform infrared Spectroscopy (FT-IR) and scanning electron microscopy (SEM) analysis. The heavy metal concentrations in a broth culture were analysed by inductively coupled plasma-optical emission spectroscopy (ICP-OES). The study suggests that PSB Cronobacter muytjensii KSCAS2 can efficiently remove the heavy metals and these bacteria could be used for the metal removal from the agricultural soils.

Occurrence of a Pempheris flavicycla in Chennai Coast, India

The sweeper fish Pempheris flavicycla is recorded from Kasimedu fish landing center, Chennai, India, for the first time.

Assessment of Anthropogenic Threats to the Biological Resources of Kaliveli Lake, India: A Coastal Wetland

Kaliveli Lake is a coastal lagoon wetlands in the Viluppuram District, near to Bay of Bengal, Tamil Nadu state, Southeast coast of India. The lake is one of the largest wetlands in peninsular India, and is considered a wetland of international importance proposed by International Union for the Conservation of Nature and Natural Resources (IUCN). Kaliveli Backwaters is 12.5 km long and 370 m broad. The average depth is 1.75 m in the high tide. At some place it shows 3.5–4.0 m deep. It covers an area of 3940 acres with a gradient from freshwater to brackish water. It is a semi-permanent, fresh to brackish water lagoon, which empties into the sea through a narrow channel connecting the wetland with the Yedayanthittu estuary to the northeast. This wetland is one of the most significant habitats suitable feeding and breeding ground for migratory birds. More than ten thousand migratory birds are visiting this wetland every year. At present, this wetland is threatened by many anthropogenic activities such as infringement from agricultural lands, wildlife poaching, loss of the surrounding forests, increased saltpan and aquaculture farming and recreational activities. The present study focuses on identification and assessment of the various threats faced by the Kaliveli wetland and we affirm following suggestions regarding the adequate measures for its conservation and management.

Isolation and molecular characterization of multidrug-resistant halophilic bacteria from shrimp farm effluents of Parangipettai coastal waters

Multidrug resistance of heterotrophic bacteria isolated from an aquaculture farm effluent in Parangipettai, at the southeastern coast of India, was investigated. In the initial screening, 27 antibiotic-resistant strains were isolated. All the strains were tested for antibiotic susceptibility against chloramphenicol with varying concentrations. From these, two highly resistant strains, i.e. S1 and S5, were isolated. The selected strains were identified by 16S ribosomal RNA (rRNA) sequencing techniques and confirmed as Bacillus pumilus and Bacillus flexus. Both the antibiotic-resistant strains were further utilized for multidrug susceptibility test by using various antibiotics. These two strains showed antibiotic resistance to 14 of 17 antibiotics tested. Both microdilution assay and well assay methods were used to determine the minimal inhibitory concentration (MIC) for the sensitive strains. Both the tests were shown to be almost similar. Our study highlights the occurrence of multidrug-resistant bacteria in the shrimp farm effluents.