Extracellular fabrication of bio-nanostructures from Ralstonia sp. strain NS-7: Characterizations and their microbiological evaluation

Sreenivasa Nayaka

doi:10.17485/ijst/v13i31.289

Abstract

Objectives: In this study, we took advantage of nanotechnology to systematically investigate the antimicrobial activity of silver nanoparticles (AgNPs) against pathogenic microorganisms. This study aimed to synthesize AgNPs from Ralstonia sp. strain NS-7 and further characterization of synthesized AgNPs. Materials: The molecular characterization of isolated strain Ralstonia sp. NS-7 was done by 16S rRNA gene sequencing and the characterizations of synthesized AgNPs was achieved by UV-Visible spectroscopy, AFM, FTIR, HRTEM, SEM, EDS and XRD. Later on, the efficacy of previously synthesized AgNPs was assessed in vitro against pathogens, such as Escherichia coli, Enterococcus faecalis, Streptococcus pneumoniae and Staphylococcus aureus. Finding: The UVvisible spectrophotometric observation of synthesized AgNPs showed maximum absorbance at 420 nm, the AFM data revealed the polydispersity of spherical nanoparticles. Further, the FTIR analysis expressed a unique IR spectral band patterning and the HR-TEM and SEM analysis showed the size of biosynthesized AgNPs in the range of 14.72 nm to 47.32 nm. The analysis of phylogenetic tree of the strain NS-7 revealed the most sequence similarity with Ralstonia sp. strain PGNP6. Finally, the AgNPs represented a broad-spectrum antimicrobial activity against gram-positive and gram-negative bacteria. Application:The biological method for the synthesis of AgNPs is eco-friendly, economical, green and non-toxic. Synthesized AgNPs from Ralstonia sp. strain NS-7 could be used as an alternative source of antimicrobial for the management of pathogenic and multi-drug resistant microorganisms. Keywords: Ralstonia sp.; FTIR; HR-TEM; 16S rRNA gene sequencing; antimicrobial activity; AgNPs

Highlights

Nanotechnology is emerging as a highly developing branch with its application in various fields of science and technology for the purpose of synthesis of new materialsNayaka et al / Indian Journal of Science and Technology 2020;13(31):3128–3140 at nanoscale range [1,2,3]
The chemical and physical methods generally utilize a large number of chemicals, require a huge space, and raise the environmental temperature, which sometimes becomes detrimental to the environment
3.2 Characterization of AgNPs 3.2.1 UV-visible spectrophotometric analysis of AgNPs The UV absorption spectrum of the AgNPs synthesized by strain NS-7 was illustrated ( Figure 2)

Summary

Introduction

Nanotechnology is emerging as a highly developing branch with its application in various fields of science and technology for the purpose of synthesis of new materialsNayaka et al / Indian Journal of Science and Technology 2020;13(31):3128–3140 at nanoscale range [1,2,3]. Nanotechnology is emerging as a highly developing branch with its application in various fields of science and technology for the purpose of synthesis of new materials. There are many techniques, which have developed for synthesizing AgNPs. But each technique of synthesizing nanoparticles solely and primarily depends on any one of biological, chemical and physical methods [4]. The biological nanoparticles can be produced from a large number of metals, such as silver, gold, platinum, zinc, copper, iron, titanium, aluminium, chromium, cobalt, nickel etc [6]. Despite this big list of metals; the AgNPs were given much attention due to its uniqueness in chemical, physical and biological properties. The green synthesis or biological synthesis of AgNPs utilizes environmental benign substances, such as leaves, flowers, stem, bark, root, even microorganisms, etc [7,8]

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