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The cell –free hemolymph and hemocytes isolated from body-fluid of marine gastropod Rapana rapiformis distributed in the shallow waters of Pondichery coast, were tested for their antibiotic potential against five common human bacterial pathogens viz. Klebsiella pneumonia, Staphylococcus aureus, Pseudomonas aeruginosa, Vibrio cholera and E.Coli. The sensitivity test thro Disc diffusion assay revealed that cell–free hemolymph of Rapana rapiformis exhibited higher level of inhibition even at MIC of 2.5ul against Vibrio cholera when compared to reference drug. A peptide molecule in haemolymph that showed higher inhibitory activity with the molecular mass of 35kDa, has been found by Sodium Dodecyl Sulphate Polyacrylamide gel electrophoresis. It could be of greater interest to isolate and characterize this protein which might be used commercially against existing antibiotic resistant strains such as MRSA in future.

Present study reports on biological synthesis of gold nanoparticles using cell free extract of Staphylococcus aureus and Escherichia coli. The cold extract is allowed to react with both 1mM and 10 mM solutions of HAuCl4 which showed a colour change from yellow to dark cherry red after 1 hr. Gold nanoparticle formation is confirmed with UV-Visible spectrophotometer at 547nm.The 10mM concentration is found to be better for synthesis of more NPs using E. coli. XRD pattern exhibited 2θ values38.18o, 44.39o, 64.58o, 77.55o of 2θ value, corresponding to Bragg’s diffraction at 111, 200, 220 and 311 plane of lattice structure closely matching with the standard values given in ICDD reference file. SEM analysis revealed morphological characteristics of nanoparticles of different sizes ranging from 70 to 200 nm. Thus, the present study throws new light on the suitability of E. coli as an alternative for conventional methods of chemical synthesis of gold nanoparticles.