ABSTRACT
Marine extremophiles are shown to tolerate extreme environmental conditions and have high metal reducing properties.Here, we report intracellular synthesis of gold nanoparticles (AuNP) by marine extremophilic bacteria Pseudoalteromonassp. Bac178 which was isolated from the OMZ of Arabian Sea. Preliminary observations suggest that these bacteria usedifferent pathways which may involves the membrane as well as intracellular proteins for the gold salt reduction. Characterization of the biosynthesised nanoparticles by various techniques such as Scanning electron microscopy (SEM),Transmission electron microscopy (TEM), X-ray diffraction (XRD) and Energy-dispersive X-ray spectroscopy (EDS)confirmed the presence of crystalline gold. These biologically synthesized AuNP were investigated for cytotoxicity andoxidative stress generation in human normal fibroblast and melanoma cells (A375). As AuNP are envisaged to find manyapplications in the medical field, it was of interest to study the effect of AuNP at the epigenetic level. They were found to benon-cytotoxic, non-genotoxic and non-oxidative stress generating over a range of concentrations. Exposure to these AuNPis observed to cause alterations in global DNA methylation as well as in the expression of DNA methyltransferase (DNMT)genes. Since biosynthesized AuNP are being used in various applications and therapies, their epigenetic modulatory activityneeds careful consideration.