Home About us MoEF Contact us Sitemap Tamil Website  
About Envis
Whats New
Microorganisms
Research on Microbes
Database
Bibliography
Publications
Library
E-Resources
Microbiology Experts
Events
Online Submission
Access Statistics

Site Visitors

blog tracking


 
Environ. Sci. Technol
Vol.,
48, No. 1, 2014; Pages: 316–322

Microbial Extracellular Polymeric Substances Reduce Ag+ to Silver Nanoparticles and Antagonize Bactericidal Activity

Fuxing Kang, Pedro J. Alvarez, and Dongqiang Zhu

State Key Laboratory of Pollution Control and Resource Reuse/School of the Environment, Nanjing University, Nanjing, Jiangsu 210046, People’s Republic of China.

Abstract

Whereas the antimicrobial mechanisms of silver have been extensively studied and exploited for numerous applications, little is known about the associated bacterial adaptation and defense mechanisms that could hinder disinfection efficacy or mitigate unintended impacts to microbial ecosystem services associated with silver release to the environment. Here, we demonstrate that extracellular polymeric substances (EPS) produced by bacteria constitute a permeability barrier with reducing constituents that mitigate the antibacterial activity of silver ions (Ag+). Specifically, manipulation of EPS in Escherichia coli suspensions (e.g., removal of EPS attached to cells by sonication/centrifugation or addition of EPS at 200 mg L-1) demonstrated its critical role in hindering intracellular silver penetration and enhancing cell growth in the presence of Ag+ (up to 0.19 mg L-1). High-resolution transmission electron microscopy (HRTEM) combined with X-ray photoelectron spectroscopy (XPS) and energy-dispersive spectrometry (EDS) analyses showed that Ag+ was reduced to silver nanoparticles (AgNPs; 10–30 nm in diameter) that were immobilized within the EPS matrix. Fourier transform infrared (FTIR) and 13C nuclear magnetic resonance (NMR) spectra suggest that Ag+reduction to AgNPs by the hemiacetal groups of sugars in EPS contributed to immobilization. Accordingly, the amount and composition of EPS produced have important implications on the bactericidal efficacy and potential environmental impacts of Ag+.

Keywords:


 
 
Copyright © 2005 ENVIS Centre ! All rights reserved
This site is optimized for 1024 x 768 screen resolution