Ecofriendly Synthesis of Silver Nanoparticles by Terrabacter humi sp. nov. and Their Antibacterial Application against Antibiotic-Resistant Pathogens

Abstract

It is essential to develop and discover alternative eco-friendly antibacterial agents due to the emergence of multi-drug-resistant microorganisms. In this study, we isolated and characterized a novel bacterium named Terrabacter humi MAHUQ-38T, utilized for the eco-friendly synthesis of silver nanoparticles (AgNPs) and the synthesized AgNPs were used to control multi-drug-resistant microorganisms. The novel strain was Gram stain positive, strictly aerobic, milky white colored, rod shaped and non-motile. The optimal growth temperature, pH and NaCl concentration were 30 °C, 6.5 and 0%, respectively. Based on 16S rRNA gene sequence, strain MAHUQ-38T belongs to the genus Terrabacter and is most closely related to several Terrabacter type strains (98.2%–98.8%). Terrabacter humi MAHUQ-38T had a genome of 5,156,829 bp long (19 contigs) with 4555 protein-coding genes, 48 tRNA and 5 rRNA genes. The culture supernatant of strain MAHUQ-38T was used for the eco-friendly and facile synthesis of AgNPs. The transmission electron microscopy (TEM) image showed the spherical shape of AgNPs with a size of 6 to 24 nm, and the Fourier transform infrared (FTIR) analysis revealed the functional groups responsible for the synthesis of AgNPs. The synthesized AgNPs exhibited strong anti-bacterial activity against multi-drug-resistant pathogens, Escherichia coli and Pseudomonas aeruginosa. Minimal inhibitory/bactericidal concentrations against E. coli and P. aeruginosa were 6.25/50 and 12.5/50 μg/mL, respectively. The AgNPs altered the cell morphology and damaged the cell membrane of pathogens. This study encourages the use of Terrabacter humi for the ecofriendly synthesis of AgNPs to control multi-drug-resistant microorganisms.

Biosynthesis, Characterization and Antibacterial Application of Novel Silver Nanoparticles against Drug Resistant Pathogenic Klebsiella pneumoniae and Salmonella Enteritidis

“…Krishnaraj et al reported that the position and form of metal NP absorption pick are strongly dependent on the size of the particle, stabilizing molecules and the bioelectricity of media [ 37 ]. Our results agree with Akter et al [ 26 ], who mentioned that the silver SPR band of Terrabacter humi mediated synthesized NPs occurred at 413 nm. The morphology (shape and size) of synthesized NPs were analyzed by FE-TEM.…”

“…MAHUQ-52 ( Figure 3 A–C), which ensured the presence of elemental silver based on the signals. In the EDX spectrum, the synthesized NPs showed a peak at 3 keV, which was due to the presence of silver nanocrystallites [ 26 ]. Two other peaks were also found due to the presence of copper grids ( Figure 3 A).…”

“…Different studies showed the biosynthesis of AgNPs using bacteria including Microvirga rosea, Paenibacillus anseongensis, Novosphingobium sp., Sporosarcina koreensis DC4, Terrabacter humi , Pseudomonas sp., etc. [ 22 , 23 , 24 , 25 , 26 , 27 ]. Rhizosphere bacteria are considered to be useful in various sectors, such as in phytoremediation, biotransformation and biosynthesis of valuable products, to increase plant growth and productivity, etc.…”

Bacterial Mediated Rapid and Facile Synthesis of Silver Nanoparticles and Their Antimicrobial Efficacy against Pathogenic Microorganisms

“…These reagents and byproducts are toxic for human health and the environment, which has led to increasing interest in biosynthesis methods. The biosynthesized nanoparticles have higher stability, lower toxicity with better physicochemical characteristics [ 26 , 27 , 28 ]. Currently, researchers are focusing more on biological approaches that include plants and their various parts and microorganisms such as bacteria, fungi, algae, etc.…”

“…Currently, researchers are focusing more on biological approaches that include plants and their various parts and microorganisms such as bacteria, fungi, algae, etc. for eco-friendly, non-toxic, and facile synthesis of MNPs [ 26 , 27 , 28 ]. Among the different biological approaches, bacterial-mediated MNPs synthesis is mostly preferred because of their high growth rate, large-scale production, ease of handling, and the possibility of genetic engineering [ 6 , 29 ].…”