Research Paper Biosynthesis of silver nanoparticles from deep sea bacterium Pseudomonas aeruginosa JQ989348 for antimicrobial, antibiofilm, and cytotoxic activity V. Ramalingam 1 , R. Rajaram 1 , C. PremKumar 2 , P. Santhanam 2 , P. Dhinesh 1 , S. Vinothkumar 1 and K. Kaleshkumar 1 1 DNA Barcoding and Marine Genomics Laboratory, Department of Marine Science, School of Marine Sciences, Bharathidasan University, Tiruchirappalli, India 2 Marine Planktonology and Aquaculture Laboratory, Department of Marine Science, School of Marine Sciences, Bharathidasan University, Tiruchirappalli, India Pseudomonas aeruginosa (JQ989348) was isolated from deep sea water sample and used for synthesis of silver nanoparticles (AgNPs). AgNPs were confirmed by analyzing surface plasmon resonance using UV–visible spectrophotometer at 420 nm. Further scanning electron microscope analysis confirmed the range of particle size between 13 and 76 nm and XRD pattern authorizes the anisotropic crystalline nature of AgNPs. Fourier transform infrared spectrum endorsed the presence of high amount of proteins and other secondary metabolites in synthesized AgNPs influence the reduction process and stabilization of nanoparticles. The inhibitory activity of AgNPs was tested against human pathogens showed high activity against Eschericia coli, Vibrio cholerae, Aeromonas sp., and Cornebacterium sp. demonstrating its antimicrobial value against pathogenic diseases. Additionally, biologically synthesized AgNPs have notable anti-biofilm activity against primary biofilm forming bacteria P. aeruginosa and Staphylococcus aureus. The MTT assay method was evaluated using human cervical cancer cells exposed the AgNPs have excellent cytotoxic activity. Keywords: Pseudomonas aeruginosa / Silver nanoparticles / Anti-microbial activity / Anti-biofilm activity / Cytotoxic activity Received: July 5, 2013; accepted: August 28, 2013 DOI 10.1002/jobm.201300514 Introduction Current interest in the field of material stabilization is to acquire an efficient protocol for the biological synthesis of AgNPs intended towards medicinal applications [1]. AgNPs were exhibit unique optical, thermal, electrical, chemical and physical properties due to combination of large proportion of high-energy surface atoms [2]. Silver is highly toxic to most microbial cells and it can be used as a biocide or antimicrobial agent [3]. The nature of silver-bacteria interactions has significant role in several biotechnological applications such as bioremediation, biomineralization, bioleaching and microbial corrosion. The biosynthesis of AgNPs by microorganisms has received more attention in recent times owing to the use as antimicrobial agents, and drug delivery [4]. Microorganisms are deemed as potential source for reduction of metallic nanoparticles such as cadmium sulfide, gold and silver [5]. Among the microorganisms prokaryotic bacteria such as Escherichia coli, Vibrio cholerae, Salmonella typhus, P. stutzeri, P. aeruginosa, and S. aureus have been utilized as reducing and stabilizing agent for bio-synthesis of nanoparticles [6]. In past, use of liquid culture of different micro- organisms for synthesis of AgNPs was predominant [7–9]. At present a rapid method for reduction of AgNPs by treating the aqueous silver nitrate solution with culture supernatants of different strains of bacteria, fungi and Correspondence: Dr. R. Rajaram, DNA Barcoding and Marine Genomics Laboratory, Department of Marine Science, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu, India E-mail: drrajaram69@rediffmail.com Phone: 0091 9842874661 Fax: 0091 431 240745 Environment  Health  Techniques 928 V. Ramalingam et al. ß 2013 WILEY-VCH Verlag GmbH & Co. KGaA,Weinheim www.jbm-journal.com J. Basic Microbiol. 2014, 54, 928–936