~ 525 ~ International Journal of Chemical Studies 2017; 5(5): 525-532 P-ISSN: 2349–8528 E-ISSN: 2321–4902 IJCS 2017; 5(5): 525-532 © 2017 IJCS Received: 12-07-2017 Accepted: 13-08-2017 Pankaj Raghuvanshi Department of Biotechnology, Dr. YS Parmar University of Horticulture & Forestry, Nauni, Solan, Himachal Pradesh, India Ankita Sharma Department of Biotechnology, Dr. YS Parmar University of Horticulture & Forestry, Nauni, Solan, Himachal Pradesh, India Himani Sharma Department of Biotechnology, Dr. YS Parmar University of Horticulture & Forestry, Nauni, Solan, Himachal Pradesh, India Shashikant Sharma Department of Biotechnology, Dr YS Parmar University of Horticulture & Forestry, Nauni, Solan (HP) 173 230 India Amna Devi Department of Biotechnology, Dr. YS Parmar University of Horticulture & Forestry, Nauni, Solan, Himachal Pradesh, India Poonam Shirkot Department of Biotechnology, Dr. YS Parmar University of Horticulture & Forestry, Nauni, Solan, Himachal Pradesh, India Anjali Chauhan Department of Soil Science and Water management, Dr. YS Parmar University of Horticulture & Forestry, Nauni, Solan, Himachal Pradesh, India Correspondence Pankaj Raghuvanshi Department of Biotechnology, Dr. YS Parmar University of Horticulture & Forestry, Nauni, Solan, Himachal Pradesh, India Biosynthesis and characterization of gold nanoparticles from plant growth promoting rhizobacteria Pankaj Raghuvanshi, Ankita Sharma, Himani Sharma, Shashikant Sharma, Amna Devi, Poonam Shirkot and Anjali Chauhan Abstract Gold nanoparticles have unique properties that make them applicable in different fields of science and technology. Thirty PGPR isolates were screened individually for their ability to synthesize gold nanoparticles which was denoted by color change from pale yellow to purple/red wine colour. Only ten were selected for further studies on the basis of maximum gold nanoparticles synthesis activity, which were further investigated for morphological and biochemical characters. PG-4 PGPR isolate showed 98% similarity with Bacillus thuringiensis strain KUDC1746, 16S ribosomal RNA, partial sequence. Phylogenetic analysis based on nucleotide sequences using NJ method show high boot strap value of 87%. These gold nanoparticles were characterized by FTIR spectrum which showed the presence of the functional groups, XRD results confirmed that these nanoparticles were originally gold nanoparticles, Scanning electron microscope results confirmed that gold nanoparticles were spherical in nature and monodispersed along with some clusters. Antibacterial activity of biosynthesized gold nanoparticles was assessed against five pathogenic bacteria and maximum inhibiton was found against Agrobacterium tumefaciens under in vitro conditions. Keywords: Gold nanoparticles, PGPRs, Bacillus thuringiensis and antibacterial activity Introduction Plant growth promoting rhizobacteria (PGPR) are a group of bacteria that enhance plant growth and yield via various plant growth promoting substances. Rhizosphere is a site with complex interactions between the root and associated microorganisms and high microbial diversity. Plant growth-promoting rhizobacteria (PGPR) are free-living, root colonizing, soil- borne bacteria exert phytostimulatory actions, when applied to seeds or crops by a combination of physiological attributes. Soil microorganisms play a very important role in maintaining soil health, ecosystem functions and crop productivity. PGPRs are known to participate in many important ecosystem processes, such as biological control of plant pathogens, nutrient cycling, and/or seedling growth. PGPRs are known to stimulate plant growth by a combination of physiological attributes such as asymbiotic nitrogen fixation phytohormones production namely indole-3-acetic acid (IAA), cytokinin, gibberellins solubilizing insoluble mineral phosphate and siderophore production. Though gold nanoparticles synthesis has been reported using various bacteria but potential of PGPRs to synthesize gold nanoparticles was worth exploring. Biologically inspired nanotechnology uses biological systems as the inspirations for new technologies and new nanotools relevant to biological or medical problems followed by refinement of the applications. The use of microorganisms to synthesize functional nanoparticles has been of great interest recently (Philip, 2009) [1] . The ability of microorganisms to change oxidation state of metals and their microbial processes has opened up new opportunity to explore novel applications such as biosynthesis of metal nanomaterials. In contrast to chemical and physical methods, microbial processes for synthesizing nanomaterials can be achieved in aqueous phase under gentle and environmentally benign conditions. Gold is one of rarest metals on earth and its importance has been known since antiquity. In addition to jewellery industry it has also found usages in diverse range of industrial applications covering the field of biology and medicine, environment and technology. Because of the increased demand of gold in form of nanoparticles, there is growing need for cost