Antibacterial mechanism of biogenic silver nanoparticles ofLactobacillus acidophilus

Abstract

The development of reliable, eco-friendly protocol for the synthesis of nanomaterials is a challenging issue in the current nanotechnology. In the present study, we reported an environmentally benign and rapid method for biogenesis of silver nanoparticles using Gram-positive bacterium Lactobacillus acidophilus which acts both as reducing and capping agent. It was observed that the culture filtrate reduced silver ions into silver nanoparticles within 24 hrs of reaction time under room temperature. The UVÀVis spectrum shows the absorbance maximum at 434 nm, which is a characteristic of surface plasmon resonance of silver. X-ray diffraction analysis showed that the nanoparticles were of facecentred cubic crystalline structure. The presence of stable spherical-shaped silver nanoparticles in the size range of 4À50 nm was determined using the transmission electron microscopy analysis. Further, these nanoparticles showed effective antibacterial activity towards Klebsiella pneumoniae. The mechanism of the silver nanoparticle bactericidal activity is discussed in terms of its interaction with the cell membrane of bacteria by causing cytolysis and leakage of proteins and carbohydrates.

Antibacterial Activity of Silver Nanoparticles: Structural Effects

“…Therefore, it becomes really difficult for bacterial cells to develop multiple simultaneous gene mutations to against NP-mediated treatments. [46] Additionally, AgNPs attaching the membrane proteins can also interfere with the uptake and release of phosphate ions, and impair respiratory chain hindering the production of energy. [43] The results showed that upon treatment with AgNPs, the surface charge of the bacteria moved toward neutral from −28.5 ± 2.9 to −3.5 ± 0.8 mV for E. coli, and from −20.6 ± 1.8 to −5.4 ± 0.5 mV for P. aeruginosa.…”

A One-Pot Synthesis and Characterization of Antibacterial Silver Nanoparticle–Cellulose Film

“…Studies have found that Ag-NPs with a size of 5-20 nm had greater antibacterial activities [2][3][4]. Currently, the widely recognized antibacterial mechanisms of Ag-NPs include disrupting the normal function of the cell wall [5], interacting with the lipid components of the cell membrane to impede its normal function [6][7][8][9][10], inducing ROS free radicals to damage the cell membrane [11][12][13], damaging the DNA structure and inhibiting its related functions [14][15][16], binding with sulfhydryl groups of enzyme proteins to make cell inactive, and so on [17,18]. Ag-NPs inhibits the characteristics of simple preparation, broad-spectrum antibacterial, strong sterilization, and less prone to emerge drug resistance, which prompted it to be used as an antibacterial agent added to ceramics [19], coatings [20], textiles [21], films [22,23], and other raw materials to fabricate antibacterial materials.…”

Molecular characterization of silver resistant E. coli strains isolated from patients suffering from diarrhea

“…The AgNPs pellet was washed by centrifugation with sterile distilled water twice for 20 min at 1000 rpm, so the culture filtrate and excess silver ions were removed. Freeze drying was used to obtain AgNPs pellet as powder for further characterization and applications (Rajesh et al, 2014).…”

“…Green synthesis using bacterial cells is considered a friendly approach for creating AgNPs in a more economic and safe way (Ghorbani, 2013). Bacterial cell enzymes such as nitrate reductase reduce Ag + ions to AgNPs, which are indicated by colorimetric reaction (Rajesh et al, 2014). Antibacterial activity of biosynthesized AgNPs has been screened against different Gram-negative isolates including E. coli indicating observable inhibitory activity (Abu-Zaid, 2016).…”