Probiotic-Mediated Biosynthesis of Silver Nanoparticles and Their Antibacterial Applications against Pathogenic Strains of Escherichia coli O157:H7

Bacillus subtilis Strain YJ-15, Isolated from the Rhizosphere of Wheat Grown under Saline Conditions, Increases Soil Fertility and Modifies Microbial Community Structure

Soil salinization during wheat cultivation considerably diminishes soil fertility and impedes wheat growth, primarily due to rhizosphere microbial community changes. Our study investigates the application of Bacillus subtilis YJ-15, a strain isolated from the rhizosphere of wheat cultivated in salinized soil, as a soil remediation agent. This strain has demonstrated significant salt tolerance, disease suppression capabilities, and growth-promoting attributes in previous studies. The wheat rhizosphere was examined to assess the impact of Bacillus subtilis YJ-15 on microbial community composition and soil fertility. Fertility of soil in saline soil was significantly increased by inoculating wheat with YJ-15. The microbial community structure within the wheat rhizosphere inoculated with Bacillus subtilis YJ-15 was analyzed through sequencing on the Illumina MiSeq platform. Phyla Proteobacteria and Acidobacteria were identified as the dominant bacteria. Basidiomycota, Mortierellomycota, and Ascomycota dominated the fungal phyla. Among the bacterial genera, Pseudomonas, Arthrobacter, and Bacillus were predominant. The predominant fungal genera included Alternaria, Cephalotrichum, Mortierella, and Chaetomium. A significant increase in Gaiella and Haliangium levels was observed in the YJ group compared to the control group. Additionally, the fungal genera Epicoccum, Sporidiobolus, and Lecythophora have significantly increased in YJ abundance. One of the potential benefits of Bacillus subtilis YJ-15 in the cultivation of wheat on salinized land is its ability to enhance the rhizosphere microbial community structure and improve soil fertility.

Effects of Deep Tillage on Wheat Regarding Soil Fertility and Rhizosphere Microbial Community

Wheat production is intrinsically linked to global food security. However, wheat cultivation is constrained by the progressive degradation of soil conditions resulting from the continuous application of fertilizers. This study aimed to examine the effects of deep tillage on rhizosphere soil microbial communities and their potential role in improving soil quality, given that the specific mechanisms driving these observed benefits remain unclear. Soil fertility in this research was evaluated through the analysis of various soil parameters, including total nitrogen, total phosphorus, total potassium, available phosphorus, and available potassium, among others. The high-throughput sequencing technique was utilized to examine the rhizosphere microbial community associated with deep tillage wheat. The findings indicated that deep tillage cultivation of wheat led to reduced fertility levels in the 0-20 cm soil layer in comparison with non-deep tillage cultivation. A sequencing analysis indicated that Acidobacteria and Proteobacteria are the dominant bacterial phyla, with Proteobacteria being significantly more abundant in the deep tillage group. The dominant fungal phyla identified were Ascomycota, Mortierellomycota, and Basidiomycota. Among bacterial genera, Arthrobacter, Bacillus, and Nocardioides were predominant, with Arthrobacter showing a significantly higher presence in the deep tillage group. The predominant fungal genera included Mortierella, Alternaria, Schizothecium, and Cladosporium. Deep tillage cultivation has the potential to enhance soil quality and boost crop productivity through the modulation of soil microbial community structure.

Synergistic interaction of nanoparticles and probiotic delivery: A review

Nanotechnology is an expanding and new technology that prompts production with nanoparticle-based (1-100 nm) organic and inorganic materials. Such a tool has an imperative function in different sectors like bioengineering, pharmaceuticals, electronics, energy, nuclear energy, and fuel, and its applications are helpful for human, animal, plant, and environmental health. In exacting, the nanoparticles are synthesized by top-down and bottom-up approaches through different techniques such as chemical, physical, and biological progress. The characterization is vital and the confirmation of nanoparticle traits is done by various instrumentation analyses like UV-Vis spectrophotometry (UV-Vis), Fourier transform infrared spectroscopy, scanning electron microscope, transmission electron microscopy, X-ray diffraction, atomic force microscopy, annular dark-field imaging, and intracranial pressure. In addition, probiotics are friendly microbes which while administered in sufficient quantity confer health advantages to the host. Characterization investigation is much more significant to the identification of good probiotics. Similarly, haemolytic activity, acid and bile salt tolerance, autoaggregation, antimicrobial compound production, inhibition of pathogens, enhance the immune system, and more health-beneficial effects on the host. The synergistic effects of nanoparticles and probiotics combined delivery applications are still limited to food, feed, and biomedical applications. However, the mechanisms by which they interact with the immune system and gut microbiota in humans and animals are largely unclear. This review discusses current research advancements to fulfil research gaps and promote the successful improvement of human and animal health.

An Emerging Foodborne Pathogen Spotlight: A Bibliometric Analysis and Scholarly Review of Escherichia coli O157 Research

Foodborne infections pose a substantial global threat, causing an estimated 600 million illnesses and resulting in approximately 420,000 deaths annually. Among the diverse array of pathogens implicated in these infections, Escherichia coli (E. coli), specifically the O157 strain (E. coli O157), emerges as a prominent pathogen associated with severe outbreaks. This study employs a comprehensive bibliometric analysis and scholarly review focused on E. coli O157 research. The bibliometric analysis highlights the significant role played by the United States in the E. coli O157 research domain. Further exploration underscores the noteworthy contributions of the researcher Doyle MP, whose body of work, consisting of 84 documents and an impressive H-Index of 49, reflects their substantial impact in the field. Recent research trends indicate a discernible shift towards innovative detection methods, exemplified by the adoption of CRISPR-CAS and Loop-Mediated Isothermal Amplification. Moreover, high-throughput whole-genome sequencing techniques are gaining prominence for the expeditious analysis of pathogenic E. coli strains. Scientists are increasingly exploring antimicrobial agents, including phage therapy, to address the challenges posed by antibiotic-resistant E. coli strains, thereby addressing critical concerns related to multi-drug resistance. This comprehensive analysis provides vital insights into the dynamic landscape of E. coli O157 research. It serves as a valuable resource for researchers, policymakers, and healthcare professionals dedicated to mitigating E. coli O157 outbreaks and advancing global public health strategies.

Optimization of the biosynthesis of silver nanoparticles using bacterial extracts and their antimicrobial potential

In the present study, silver nanoparticles (AgNPs) were biosynthesized using the supernatant and the intracellular extract of Cupriavidus necator, Bacillus megaterium, and Bacillus subtilis. The characterization of the AgNPs was carried out using UV-Vis spectroscopy, FTIR, DLS and TEM. Resazurin microtiter-plate assay was used to determine the antimicrobial action of AgNPs against Escherichia coli. UV-Visible spectra showed peaks between 414 and 460 nm. TEM analysis revealed that the synthesized AgNPs showed mostly spherical shapes. DLS results determined sizes from 20.8 to 118.4 nm. The highest antimicrobial activity was obtained with the AgNPs synthesized with supernatant rather than those using the intracellular extract. Therefore, it was determined that the bacterial species, temperature, pH, and type of extract (supernatant or intracellular) influence the biosynthesis. This synthesis thus offers a simple, environmentally friendly, and low-cost method for the production of AgNPs, which can be used as antibacterial agents.

Bioactive ZnO Nanoparticles: Biosynthesis, Characterization and Potential Antimicrobial Applications

In recent years, biosynthesized zinc oxide nanoparticles (ZnONPs) have gained tremendous attention because of their safe and non-toxic nature and distinctive biomedical applications. A diverse range of microbes (bacteria, fungi and yeast) and various parts (leaf, root, fruit, flower, peel, stem, etc.) of plants have been exploited for the facile, rapid, cost-effective and non-toxic synthesis of ZnONPs. Plant extracts, microbial biomass or culture supernatant contain various biomolecules including enzymes, amino acids, proteins, vitamins, alkaloids, flavonoids, etc., which serve as reducing, capping and stabilizing agents during the biosynthesis of ZnONPs. The biosynthesized ZnONPs are generally characterized using UV-VIS spectroscopy, TEM, SEM, EDX, XRD, FTIR, etc. Antibiotic resistance is a serious problem for global public health. Due to mutation, shifting environmental circumstances and excessive drug use, the number of multidrug-resistant pathogenic microbes is continuously rising. To solve this issue, novel, safe and effective antimicrobial agents are needed urgently. Biosynthesized ZnONPs could be novel and effective antimicrobial agents because of their safe and non-toxic nature and powerful antimicrobial characteristics. It is proven that biosynthesized ZnONPs have strong antimicrobial activity against various pathogenic microorganisms including multidrug-resistant bacteria. The possible antimicrobial mechanisms of ZnONPs are the generation of reactive oxygen species, physical interactions, disruption of the cell walls and cell membranes, damage to DNA, enzyme inactivation, protein denaturation, ribosomal destabilization and mitochondrial dysfunction. In this review, the biosynthesis of ZnONPs using microbes and plants and their characterization have been reviewed comprehensively. Also, the antimicrobial applications and mechanisms of biosynthesized ZnONPs against various pathogenic microorganisms have been highlighted.

Bacterial mediated green synthesis of silver nanoparticles and their antibacterial and antifungal activities against drug-resistant pathogens

In the healthcare sector, the production of bioactive silver nanoparticles (AgNPs) with antimicrobial properties is of great importance. In this study, a novel bacterial strain, Paenibacillus sp. MAHUQ-63, was identified as a potential candidate for facile and rapid biosynthesis of AgNPs. The synthesized AgNPs were used to control the growth of human pathogens, Salmonella Enteritidis and Candida albicans. The bacterial culture supernatant was used to synthesize the nanoparticles (NPs). Field emission transmission electron microscope examination showed spherical-shaped NPs with 15-55 nm in size. Fourier transform-infrared analysis identified various functional groups. The synthesized AgNPs demonstrated remarkable activity against S. Enteritidis and C. albicans. The zones of inhibition for 100 µl (0.5 mg ml-1) of AgNPs against S. Enteritidis and C. albicans were 18.0 ± 1.0 and 19.5 ± 1.3 mm, respectively. The minimum inhibitory concentrations were 25.0 and 12.5 µg ml-1 against S. Enteritidis and C. albicans, respectively. Additionally, the minimum bactericidal concentrations were 25.0 µg ml-1 against both pathogenic microbes. The field emission scanning electron microscopy analysis showed that the treatment of AgNPs caused morphological and structural damage to both S. Enteritidis and C. albicans. Therefore, these AgNPs can be used as a new and effective antimicrobial agent.

Combating Microbial Infections Using Metal-Based Nanoparticles as Potential Therapeutic Alternatives

The nature of microorganisms and the efficiency of antimicrobials have witnessed a huge co-dependent change in their dynamics over the last few decades. On the other side, metals and metallic compounds have gained popularity owing to their effectiveness against various microbial strains. A structured search of both research and review papers was conducted via different electronic databases, such as PubMed, Bentham, Springer, and Science Direct, among others, for the present review. Along with these, marketed products, patents, and Clinicaltrials.gov were also referred to for our review. Different microbes such as bacteria, fungi, etc., and their diverse species and strains have been reviewed and found to be sensitive to metal-carrying formulations. The products are observed to restrict growth, multiplication, and biofilm formation effectively and adequately. Silver has an apt use in this area of treatment and recovery, and other metals like copper, gold, iron, and gallium have also been observed to generate antimicrobial activity. The present review identified membrane disruption, oxidative stress, and interaction with proteins and enzymes to be the primary microbicidal processes. Elaborating the action, nanoparticles and nanosystems are shown to work in our favor in well excelled and rational ways.

Biogenic Silver Nanoparticles Produced by Soil Rare Actinomycetes and Their Significant Effect on Aspergillus-derived mycotoxins

The current investigation addressed the green synthesis of silver nanoparticles (AgNPs) using newly isolated silver-resistant rare actinomycetes, Glutamicibacter nicotianae SNPRA1 and Leucobacter aridicollis SNPRA2, and investigated their impact on the mycotoxigenic fungi Aspergillus flavus ATCC 11498 and Aspergillus ochraceus ATCC 60532. The formation of AgNPs was evidenced by the reaction's color change to brownish and the appearance of the characteristic surface plasmon resonance. The transmission electron microscopy of biogenic AgNPs produced by G. nicotianae SNPRA1 and L. aridicollis SNPRA2 (designated Gn-AgNPs and La-AgNPs, respectively) revealed the generation of monodispersed spherical nanoparticles with average sizes of 8.48 ± 1.72 nm and 9.67 ± 2.64 nm, respectively. Furthermore, the XRD patterns reflected their crystallinity and the FTIR spectra demonstrated the presence of proteins as capping agents. Both bioinspired AgNPs exhibited a remarkable inhibitory effect on the conidial germination of the investigated mycotoxigenic fungi. The bioinspired AgNPs caused an increase in DNA and protein leakage, suggesting the disruption of membrane permeability and integrity. Interestingly, the biogenic AgNPs completely inhibited the production of total aflatoxins and ochratoxin A at concentrations less than 8 μg/mL. At the same time, cytotoxicity investigations revealed the low toxicity of the biogenic AgNPs against the human skin fibroblast (HSF) cell line. Both biogenic AgNPs exhibited feasible biocompatibility with HSF cells at concentrations up to 10 μg/mL and their IC₅₀ values were 31.78 and 25.83 μg/mL for Gn-AgNPs and La-AgNPs, respectively. The present work sheds light on the antifungal prospect of the biogenic AgNPs produced by rare actinomycetes against mycotoxigenic fungi as promising candidates to combat mycotoxin formation in food chains at nontoxic doses.

Biosynthesis of silver nanoparticles using Pseudomonas canadensis, and its antivirulence effects against Pseudomonas tolaasii, mushroom brown blotch agent

This study reports the biosynthesis of silver nanoparticles (AgNPs) using a Pseudomonas canadensis Ma1 strain isolated from wild-growing mushrooms. Freshly prepared cells of P. canadensis Ma1 incubated at 26-28 °C with a silver nitrate solution changed to a yellowish brown color, indicating the formation of AgNPs, which was confirmed by UV-Vis spectroscopy, scanning electron microscopy (SEM), and X-ray diffraction. SEM analysis showed spherical nanoparticles with a distributed size mainly between 21 and 52 nm, and the XRD pattern revealed the crystalline nature of AgNPs. Also, it provides an evaluation of the antimicrobial activity of the biosynthesized AgNPs against Pseudomonas tolaasii Pt18, the causal agent of mushroom brown blotch disease. AgNPs were found to be bioactive at 7.8 μg/ml showing a minimum inhibitory concentration (MIC) effect against P. tolaasii Pt18 strain. AgNPs at the MIC level significantly reduced virulence traits of P. tolaasii Pt18 such as detoxification of tolaasin, various motility behavior, chemotaxis, and biofilm formation which is important for pathogenicity. Scanning electron microscopy (SEM) revealed that bacterial cells treated with AgNPs showed a significant structural abnormality. Results showed that AgNPs reduced brown blotch symptoms in vivo. This research demonstrates the first helpful use of biosynthesized AgNPs as a bactericidal agent against P. tolaasii.

Biosynthesis of Metal and Metal Oxide Nanoparticles Using Microbial Cultures: Mechanisms, Antimicrobial Activity and Applications to Cultural Heritage

Nanoparticles (1 to 100 nm) have unique physical and chemical properties, which makes them suitable for application in a vast range of scientific and technological fields. In particular, metal nanoparticle (MNPs) research has been showing promising antimicrobial activities, paving the way for new applications. However, despite some research into their antimicrobial potential, the antimicrobial mechanisms are still not well determined. Nanoparticles' biosynthesis, using plant extracts or microorganisms, has shown promising results as green alternatives to chemical synthesis; however, the knowledge regarding the mechanisms behind it is neither abundant nor consensual. In this review, findings from studies on the antimicrobial and biosynthesis mechanisms of MNPs were compiled and evidence-based mechanisms proposed. The first revealed the importance of enzymatic disturbance by internalized metal ions, while the second illustrated the role of reducing and negatively charged molecules. Additionally, the main results from recent studies (2018-2022) on the biosynthesis of MNPs using microorganisms were summarized and analyzed, evidencing a prevalence of research on silver nanoparticles synthesized using bacteria aiming toward testing their antimicrobial potential. Finally, a synopsis of studies on MNPs applied to cultural heritage materials showed potential for their future use in preservation.

Chitosan-Coated Polymeric Silver and Gold Nanoparticles: Biosynthesis, Characterization and Potential Antibacterial Applications: A Review

Biosynthesized metal nanoparticles, especially silver and gold nanoparticles, and their conjugates with biopolymers have immense potential in various fields of science due to their enormous applications, including biomedical applications. Polymeric nanoparticles are particles of small sizes from 1 nm to 1000 nm. Among different polymeric nanoparticles, chitosan-coated silver and gold nanoparticles have gained significant interest from researchers due to their various biomedical applications, such as anti-cancer, antibacterial, antiviral, antifungal, anti-inflammatory technologies, as well as targeted drug delivery, etc. Multidrug-resistant pathogenic bacteria have become a serious threat to public health day by day. Novel, effective, and safe antibacterial agents are required to control these multidrug-resistant pathogenic microorganisms. Chitosan-coated silver and gold nanoparticles could be effective and safe agents for controlling these pathogens. It is proven that both chitosan and silver or gold nanoparticles have strong antibacterial activity. By the conjugation of biopolymer chitosan with silver or gold nanoparticles, the stability and antibacterial efficacy against multidrug-resistant pathogenic bacteria will be increased significantly, as well as their toxicity in humans being decreased. In recent years, chitosan-coated silver and gold nanoparticles have been increasingly investigated due to their potential applications in nanomedicine. This review discusses the biologically facile, rapid, and ecofriendly synthesis of chitosan-coated silver and gold nanoparticles; their characterization; and potential antibacterial applications against multidrug-resistant pathogenic bacteria.

Characterization of Genomic Diversity among Carbapenem-Resistant Escherichia coli Clinical Isolates and Antibacterial Efficacy of Silver Nanoparticles from Pakistan

The emergence of carbapenem-resistant Escherichia coli (E. coli) is considered an important threat to public health resulting in resistance accumulation due to antibiotics misuse and selection pressure. This warrants periodic efforts to investigate and develop strategies for infection control. A total of 184 carbapenem-resistant clinical strains of E. coli were characterized for resistance pattern, resistance genes, plasmids, sequence types and in vitro efficacy of silver nanoparticles (AgNPs). Carbapenem resistance was prevalent in E. coli isolated from female patients (64.7%), urine samples (40.8%) and surgical wards (32.1%). Polymyxin-B showed higher susceptibility. ESBLs and carbapenemases were produced in 179 and 119 isolates, respectively. Carbapenemase-encoding genes were observed among 104 strains with blaNDM-1 (45.1%), blaOXA-48 (27%), blaNDM-7 (3.8%), blaNDM-1/blaOXA-48 (15.4%), blaNDM-7/blaOXA-48 (2.9%), blaOXA-48/blaVIM (3.8%) and blaNDM-1/blaVIM (2%). ESBL resistance genes were detected in 147 isolates, namely blaSHV (24.9%), blaCTX-M (17.7%), blaTEM (4.8%), blaSHV/blaCTX-M (29.2%), blaSHV/blaTEM (15%) and blaCTX-M/blaTEM (8.8%). ST405 (44.4%) and ST131 (29.2%) were more frequent sequence types with ST101 (9.7%), ST10 (9.7%) and ST648 (7%). The replicon types IncFII, IncFIIK, IncA/C, IncN and IncL/M were detected. The combination of MEM/AgNPs remained effective against carbapenemase-positive E. coli. We reported genetically diverse E. coli strains coharboring carbapenemases/ESBLs from Pakistan. Moreover, this study highlights the enhanced antibacterial activity of MEM/AgNPs and may be used to manage bacterial infections.

Characterization of the biosynthesized intracellular and extracellular plasmonic silver nanoparticles using Bacillus cereus and their catalytic reduction of methylene blue

The biosynthesis of silver nanoparticles (Ag NPs) has been studied in detail using two different approaches. For the first time, Bacillus cereus is used for one-pot biosynthesis of capsulated Ag NPs, using both intracellular and extracellular approaches. To discriminate between the produced nanostructures by these two approaches, their structures, nanomorphologies, optical properties, hydrodynamic sizes and zeta potentials are studied using different techniques. Fourier-transform infrared spectroscopy was used to identify the bioactive components responsible for the reduction of Ag+ ions into Ag and the growth of stable Ag NPs. Scanning and transmission electron microscopy images displayed spherical and polygon nanomorphology for the intracellular and extracellular biosynthesized Ag NPs. For intracellular and extracellular biosynthesized Ag NPs, a face-centred cubic structure was observed, with average crystallite sizes of 45.4 and 90.8 nm, respectively. In comparison to the noncatalytic reduction test, the catalytic activities of intracellular and extracellular biosynthesized Ag NPs were explored for the reduction of highly concentrated MB dye solution. Extracellular Ag NPs achieved 100% MB reduction efficacy after around 80 min, compared to 50.6% and 24.1% in the presence and absence of intracellular Ag NPs, respectively. The rate of MB reduction was boosted by 22 times with the extracellular catalyst, and by 3 times with the intracellular catalyst. Therefore, the extracellular production process of Ag NPs utilizing Bacillus cereus bacteria might be applied in the industry as a cost-effective way for eliminating the toxic MB dye.