JOURNAL OF PURE AND APPLIED MICROBIOLOGY, June 2013. Vol. 7(2), p. Proof * To whom all correspondence should be addressed. E-mail: v.mohan@vit.ac.in Studies on the Inhibitory Activity of Biologically Synthesized and Characterized Zinc Oxide Nanoparticles using Lactobacillus sporogens against Staphylococcus aureus Mudit Mishra, Jeny Singh Paliwal, Suneet Kumar Singh, E Selvarajan, C.Subathradevi and V. Mohanasrinivasan* School of Bio sciences and Technology, VIT University, Vellore-14, India. (Received: 09 September 2012; accepted: 06 November 2012) In present scenario the science and engineering of nanosystems is one of the most challenging and fastest growing sectors of nanobiotechnology. Biologically synthesised nanoparticles are the most efficient miniaturized functional materials that are constructed and engineered to exert specific functions with enormous ability. Micro-organisms have this extraordinary capacity to form such exquisite nanostructures. This research work reports the biological synthesis of zinc oxide nanoparticles using a probiotic bacteria Lactobacillus sporogens. To ascertain the formation of zinc oxide nanoparticles X-Ray Diffractometer (XRD), Fourier Transform Infra-Red Spectroscopy (FTIR) and UV-Visible Spectroscopy were performed. XRD analysis indicated that the zinc oxide nanoparticle has hexagonal unit cell structure with the average particle size of 145.7 nm. The synthesised nanoparticles were found to be effective against Staphylococcus aureus. Key words Lactobacillus sporogens. Zinc oxide, Biogenic nanoparticle, Inhibitory activity. Nanotechnology and nanomaterial’s is a very promising technology that provide a broad range of novel uses and also has a huge potential in the field of biomedical and life sciences. The properties of a material are greatly altered because of the increase in surface to volume ratio that leads to increase in the dominance of the behaviour of atoms on the surface to that of in the interior of the particle. There are a variety of ways to synthesize different types of nanoparticles, it could be a physical, chemical, biological and even hybrid methods. Physical and chemical methods are popular methods of synthesising nanoparticles but because of their toxicity levels their application is limited and these methods are costly too. K. M. Reddy et al 2007 demonstrated that the Introduction of ~13 nm ZnO NP kills gramnegative E. coli at concentrations 3.4 mM, whereas growth of gram-positive S. aureus was prevented at much lower concentrations (1 mM). Importantly, human T-cells are considerably more resistant to NP toxicity than either E. coli or S. aureus. These findings suggest that ZnO NP may potentially prove useful as nanomedicine based antimicrobial agents at selective therapeutic dosing regimes. Therefore a method was needed for the synthesis of nanoparticles which would be cheaper, non-toxic and eco-friendly. For such purpose microorganisms can be exploited to synthesise nanoparticles. Nanoparticles which are produced by “biogenic” enzymatic process have varied applications and they can be readily used in clinical areas also. Bacteria and fungi have been naturally bestowed with this property of reducing or oxidising metal