Extracellular biosynthesis of silver nanoparticles using Streptomyces griseoplanus SAI-25 and its antifungal activity against Macrophomina phaseolina , the charcoal rot pathogen of sorghum

Bioactive Streptomycetes: A Powerful Tool to Synthesize Diverse Nanoparticles With Multifarious Properties

Nanobiotechnology has gained significant attention due to its capacity to generate substantial benefits through the integration of microbial biotechnology and nanotechnology. Among microbial organisms, Actinomycetes, particularly the prominent genus Streptomycetes, have garnered attention for their prolific production of antibiotics. Streptomycetes have emerged as pivotal contributors to the discovery of a substantial number of antibiotics and play a dominant role in combating infectious diseases on a global scale. Despite the noteworthy progress achieved through the development and utilization of antibiotics to combat infectious pathogens, the prevalence of infectious diseases remains a prominent cause of mortality worldwide, particularly among the elderly and children. The emergence of antibiotic resistance among pathogens has diminished the efficacy of antibiotics in recent decades. Nevertheless, Streptomycetes continue to demonstrate their potential by producing bioactive metabolites for the synthesis of nanoparticles. Streptomycetes are instrumental in producing nanoparticles with diverse bioactive characteristics, including antiviral, antibacterial, antifungal, antioxidant, and antitumor properties. Biologically synthesized nanoparticles have exhibited a meaningful reduction in the impact of antibiotic resistance, providing resources for the development of new and effective drugs. This review succinctly outlines the significant applications of Streptomycetes as a crucial element in nanoparticle synthesis, showcasing their potential for diverse and enhanced beneficial applications.

Fine-scale characterization of the soybean rhizosphere microbiome via synthetic long reads and avidity sequencing

BACKGROUND

The rhizosphere microbiome displays structural and functional dynamism driven by plant, microbial, and environmental factors. While such plasticity is a well-evidenced determinant of host health, individual and community-level microbial activity within the rhizosphere remain poorly understood, due in part to the insufficient taxonomic resolution achieved through traditional marker gene amplicon sequencing. This limitation necessitates more advanced approaches (e.g., long-read sequencing) to derive ecological inferences with practical application. To this end, the present study coupled synthetic long-read technology with avidity sequencing to investigate eukaryotic and prokaryotic microbiome dynamics within the soybean (Glycine max) rhizosphere under field conditions.

RESULTS

Synthetic long-read sequencing permitted de novo reconstruction of the entire 18S-ITS1-ITS2 region of the eukaryotic rRNA operon as well as all nine hypervariable regions of the 16S rRNA gene. All full-length, mapped eukaryotic amplicon sequence variants displayed genus-level classification, and 44.77% achieved species-level classification. The resultant eukaryotic microbiome encompassed five kingdoms (19 genera) of protists in addition to fungi - a depth unattainable with conventional short-read methods. In the prokaryotic fraction, every full-length, mapped amplicon sequence variant was resolved at the species level, and 23.13% at the strain level. Thirteen species of Bradyrhizobium were thereby distinguished in the prokaryotic microbiome, with strain-level identification of the two Bradyrhizobium species most reported to nodulate soybean. Moreover, the applied methodology delineated structural and compositional dynamism in response to experimental parameters (i.e., growth stage, cultivar, and biostimulant application), unveiled a saprotroph-rich core microbiome, provided empirical evidence for host selection of mutualistic taxa, and identified key microbial co-occurrence network members likely associated with edaphic and agronomic properties.

CONCLUSIONS

This study is the first to combine synthetic long-read technology and avidity sequencing to profile both eukaryotic and prokaryotic fractions of a plant-associated microbiome. Findings herein provide an unparalleled taxonomic resolution of the soybean rhizosphere microbiota and represent significant biological and technological advancements in crop microbiome research.

Exploring the Potential of Halotolerant Actinomycetes from Rann of Kutch, India: A Study on the Synthesis, Characterization, and Biomedical Applications of Silver Nanoparticles

A tremendous increase in the green synthesis of metallic nanoparticles has been noticed in the last decades, which is due to their unique properties at the nano dimension. The present research work deals with synthesis mediated by the actinomycete Streptomyces tendae of silver nanoparticles (AgNPs), isolated from Little and Greater Rann of Kutch, India. The confirmation of the formation of AgNPs by the actinomycetes was carried out by using a UV-Vis spectrophotometer where an absorbance peak was obtained at 420 nm. The X-ray diffraction pattern demonstrated five characteristic diffraction peaks indexed at the lattice plane (111), (200), (231), (222), and (220). Fourier transform infrared showed typical bands at 531 to 1635, 2111, and 3328 cm-1. Scanning electron microscopy shows that the spherical-shaped AgNPs particles have diameters in the range of 40 to 90 nm. The particle size analysis displayed the mean particle size of AgNPs in aqueous medium, which was about 55 nm (±27 nm), bearing a negative charge on their surfaces. The potential of the S. tendae-mediated synthesized AgNPs was evaluated for their antimicrobial, anti-methicillin-resistant Staphylococcus aureus (MRSA), anti-biofilm, and anti-oxidant activity. The maximum inhibitory effect was observed against Pseudomonas aeruginosa at (8 µg/mL), followed by Escherichia coli and Aspergillus niger at (32 µg/mL), and against Candida albicans (64 µg/mL), whereas Bacillus subtilis (128 µg/mL) and Staphylococcus aureus (256 µg/mL) were much less sensitive to AgNPs. The biosynthesized AgNPs displayed activity against MRSA, and the free radical scavenging activity was observed with an increase in the dosage of AgNPs from 25 to 200 µg/mL. AgNPs in combination with ampicillin displayed inhibition of the development of biofilm in Pseudomonas aeruginosa and Streptococcus pneumoniae at 98% and 83%, respectively. AgNPs were also successfully coated on the surface of cotton to prepare antimicrobial surgical cotton, which demonstrated inhibitory action against Bacillus subtilis (15 mm) and Escherichia coli (12 mm). The present research integrates microbiology, nanotechnology, and biomedical science to formulate environmentally friendly antimicrobial materials using halotolerant actinomycetes, evolving green nanotechnology in the biomedical field. Moreover, this study broadens the understanding of halotolerant actinomycetes and their potential and opens possibilities for formulating new antimicrobial products and therapies.

Long-Term Benefits of Cenchrus fungigraminus Residual Roots Improved the Quality and Microbial Diversity of Rhizosphere Sandy Soil through Cellulose Degradation in the Ulan Buh Desert, Northwest China

Long-term plant residue retention can effectively replenish soil quality and fertility. In this study, we collected rhizosphere soil from the residual roots of annual Cenchrus fungigraminus in the Ulan Buh Desert over the past 10 years. The area, depth, and length of these roots decreased over time. The cellulose content of the residual roots was significantly higher in the later 5 years (2018-2022) than the former 5 years (2013-2017), reaching its highest value in 2021. The lignin content of the residual roots did not differ across samples except in 2015 and reached its highest level in 2021. The total sugar of the residual roots in 2022 was 227.88 ± 30.69 mg·g-1, which was significantly higher than that in other years. Compared to the original sandy soil, the soil organic matter and soil microbial biomass carbon (SMBC) contents were 2.17-2.41 times and 31.52-35.58% higher in the later 3 years (2020-2022) and reached the highest values in 2020. The residual roots also significantly enhanced the soil carbon stocks from 2018-2022. Soil dehydrogenase, nitrogenase, and N-acetyl-β-D-glucosidase (S-NAG) were significantly affected from 2019-2022. The rhizosphere soil community richness and diversity of the bacterial and fungal communities significantly decreased with the duration of the residual roots in the sandy soil, and there was a significant difference for 10 years. Streptomyces, Bacillus, and Sphigomonas were the representative bacteria in the residual root rhizosphere soil, while Agaricales and Panaeolus were the enriched fungal genera. The distance-based redundancy analysis and partial least square path model results showed that the duration of residual roots in the sandy soil, S-NAG, and SMBC were the primary environmental characteristics that shaped the microbial community. These insights provide new ideas on how to foster the exploration of the use of annual herbaceous plants for sandy soil improvement in the future.

Tiny but mighty: metal nanoparticles as effective antimicrobial agents for plant pathogen control

Metal nanoparticles (MNPs) have gained significant attention in recent years for their potential use as effective antimicrobial agents for controlling plant pathogens. This review article summarizes the recent advances in the role of MNPs in the control of plant pathogens, focusing on their mechanisms of action, applications, and limitations. MNPs can act as a broad-spectrum antimicrobial agent against various plant pathogens, including bacteria, fungi, and viruses. Different types of MNPs, such as silver, copper, zinc, iron, and gold, have been studied for their antimicrobial properties. The unique physicochemical properties of MNPs, such as their small size, large surface area, and high reactivity, allow them to interact with plant pathogens at the molecular level, leading to disruption of the cell membrane, inhibition of cellular respiration, and generation of reactive oxygen species. The use of MNPs in plant pathogen control has several advantages, including their low toxicity, selectivity, and biodegradability. However, their effectiveness can be influenced by several factors, including the type of MNP, concentration, and mode of application. This review highlights the current state of knowledge on the use of MNPs in plant pathogen control and discusses the future prospects and challenges in the field. Overall, the review provides insight into the potential of MNPs as a promising alternative to conventional chemical agents for controlling plant pathogens.

Tiny but Mighty: Nanoscale Materials in Plant Disease Management

Nanoscale materials are promising tools for managing plant diseases and are becoming important players in the current agritech revolution. However, adopting modern methodologies requires a broad understanding of their effectiveness in solving target problems and their effects on the environment and food chain. Furthermore, it is paramount that such technologies are mechanistically and economically feasible for growers to adopt in order to be sustainable in the long run. This Feature Article summarizes the latest findings on the role of nanoscale materials in managing agricultural plant pathogens. Herein, we discussed the benefits and limitations of using nanoscale materials in plant disease management and their potential impacts on the environment and global food security.

Nanobiotechnology in crop stress management: an overview of novel applications

Agricultural crops are subject to a variety of biotic and abiotic stresses that adversely affect growth and reduce the yield of crop plantss. Traditional crop stress management approaches are not capable of fulfilling the food demand of the human population which is projected to reach 10 billion by 2050. Nanobiotechnology is the application of nanotechnology in biological fields and has emerged as a sustainable approach to enhancing agricultural productivity by alleviating various plant stresses. This article reviews innovations in nanobiotechnology and its role in promoting plant growth and enhancing plant resistance/tolerance against biotic and abiotic stresses and the underlying mechanisms. Nanoparticles, synthesized through various approaches (physical, chemical and biological), induce plant resistance against these stresses by strengthening the physical barriers, improving plant photosynthesis and activating plant defense mechanisms. The nanoparticles can also upregulate the expression of stress-related genes by increasing anti-stress compounds and activating the expression of defense-related genes. The unique physico-chemical characteristics of nanoparticles enhance biochemical activity and effectiveness to cause diverse impacts on plants. Molecular mechanisms of nanobiotechnology-induced tolerance to abiotic and biotic stresses have also been highlighted. Further research is needed on efficient synthesis methods, optimization of nanoparticle dosages, application techniques and integration with other technologies, and a better understanding of their fate in agricultural systems.

Nanotechnology - A new frontier of nano-farming in agricultural and food production and its development

The potential of nanotechnology for the development of sustainable agriculture has been promising. The initiatives to meet the rising food needs of the rapidly growing world population are mainly powered by sustainable agriculture. Nanoparticles are used in agriculture due to their distinct physicochemical characteristics. The interaction of nanomaterials with soil components is strongly determined in terms of soil quality and plant growth. Numerous research has been carried out to investigate how nanoparticles affect the growth and development of plants. Nanotechnology has been applied to improve the quality and reduce post-harvest loss of agricultural products by extending their shelf life, particularly for fruits and vegetables. This review assesses the latest literature on nanotechnology, which is used as a nano-biofertilizer as seen in the agricultural field for high productivity and better growth of plants, an important source of balanced nutrition for the crop, seed germination, and quality enrichment. Additionally, post-harvest food processing and packaging can benefit greatly from the use of nanotechnology to cut down on food waste and contamination. It also critically discusses the mechanisms involved in nanoparticle absorption and translocation within the plants and the synthesis of green nanoparticles.

Optimized Green Synthesis and Anticancer Potential of Silver Nanoparticles Using Juniperus procera Extract Against Lung Cancer Cells

Silver nanoparticles (AgNPs) have been considered promising candidates for medical practices in various fields. This study proposed an efficient, economical, uncomplicated, and reliable method to synthesize AgNPs utilizing leaf and fruit extracts of Juniperus procera (J. procera) as capping, reducing, and stabilizing agents. The study includes optimizing the green synthesis conditions to produce stable AgNPs with high yields, acceptable particle size, and shape, hence, AgNPs may be used for different medical purposes through the improvement of their properties. Several spectroscopic and other analyses performed characterization of the fabricated AgNPs, and the results show stable and spherical AgNPs between 14 and 18 nm in size. The study also evaluated the anticancer activities of the biosynthesized AgNPs using J. procera fruit and leaf extracts against in vitro lung cancer A549 and H1975 cells. The results demonstrate the high toxicity of the biosynthesized AgNPs against in vitro lung cancer cells, supporting therapeutic and biomedical applications of AgNPs.

Green Metallic Nanoparticles: Biosynthesis to Applications

Current advancements in nanotechnology and nanoscience have resulted in new nanomaterials, which may pose health and environmental risks. Furthermore, several researchers are working to optimize ecologically friendly procedures for creating metal and metal oxide nanoparticles. The primary goal is to decrease the adverse effects of synthetic processes, their accompanying chemicals, and the resulting complexes. Utilizing various biomaterials for nanoparticle preparation is a beneficial approach in green nanotechnology. Furthermore, using the biological qualities of nature through a variety of activities is an excellent way to achieve this goal. Algae, plants, bacteria, and fungus have been employed to make energy-efficient, low-cost, and nontoxic metallic nanoparticles in the last few decades. Despite the environmental advantages of using green chemistry-based biological synthesis over traditional methods as discussed in this article, there are some unresolved issues such as particle size and shape consistency, reproducibility of the synthesis process, and understanding of the mechanisms involved in producing metallic nanoparticles via biological entities. Consequently, there is a need for further research to analyze and comprehend the real biological synthesis-dependent processes. This is currently an untapped hot research topic that required more investment to properly leverage the green manufacturing of metallic nanoparticles through living entities. The review covers such green methods of synthesizing nanoparticles and their utilization in the scientific world.

Microbe-oriented nanoparticles as phytomedicines for plant health management: An emerging paradigm to achieve global food security

Biotic and abiotic environmental stresses affect the production and quality of agricultural products worldwide. The extensive use of traditional preventive measures comprising toxic chemicals has become more problematic due to severe ecotoxicological challenges. To address this issue, engineered nanoparticles (NPs) with their distinct physical and chemical properties has gained scientific attention and can help plants to confront environmental challenges. Despite their ameliorative and beneficial effects, toxicological concerns have been raised about NPs. The recent development of biogenic NPs (bio-NPs) is getting attention in agriculture due to their diverse biocompatibility, better functional efficacy, and eco-friendly nature compared to the recalcitrant NPs, providing a promising strategy for increased crop protection against biotic and abiotic environmental stresses, with the ultimate goal of ensuring global food security. This review summarizes the recent advances in the engineering of bio-NPs with particular emphasis on the functions of bio-NPs in protecting plants from biotic and abiotic environmental stresses, delivery and entry routes of NPs to plant systems, nanotoxicity, and plant physiological/biochemical responses to nanotoxicity. Future perspectives of bio-NP-enabled strategies, remaining pitfalls, and possible solutions to combat environmental challenges via advanced nanotechnology to achieve global food security and a sustainable agricultural system are also discussed.

Trichogenic Silver-Based Nanoparticles for Suppression of Fungi Involved in Damping-Off of Cotton Seedlings

Mycogenic silver nanoparticles (AgNPs) produced by some biocontrol agents have shown the ability to inhibit the growth of numerous plant pathogenic fungi, which may be a unique method of disease management. This study describes the extracellular production of AgNPs by Trichoderma harzianum. The size, shape, charge, and composition of the AgNPs were subsequently studied by UV-visible spectroscopy, DLS, zeta potential, TEM, SEM, and EDX, among other methods. The AgNPs had sizes ranging from 6 to 15 nm. The antifungal activities of bio-synthesized AgNPs and two commercial fungicides (Moncut and Maxim XL) were tested against three soil-borne diseases (Fusarium fujikuroi, Rhizoctonia solani, and Macrophomina phaseolina). Cotton seedling illnesses were significantly reduced under greenhouse settings after significant in vitro antifungal activity was documented for the control of plant pathogenic fungi. The use of biocontrol agents such as T. harzianum, for example, may be a safe strategy for synthesizing AgNPs and using them to combat fungus in Egyptian cotton.

Green synthesis of Silver nanoparticles using Streptomyces hirsutus strain SNPGA-8 and their characterization, antimicrobial activity, and anticancer activity against human lung carcinoma cell line A549

The current study described the systematic and detailed extracellular synthesis method of silver nanoparticles (AgNPs) using Streptomyces hirsutus strain SNPGA-8 by green synthesis method. The AgNPs were subjected for characterizations using UV-Vis, FTIR, TGA, TEM, EDX, XRD, and zeta-potential analyses. The antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecalis, Escherichia coli, Candida albicans, Alternaria alternata, Candida glabrata and Fusarium oxysporum was determined by the agar well diffusion technique. The cytotoxicity of AgNPs against human lung cancer (A549) was studied by MTT and ROS assays and capping of proteins of AgNPs from SDS-PAGE. In the UV-Vis., absorption peak was found at 418 nm, FTIR analysis revealed the infrared bands of specific functional groups from 3273 cm-1 to 428 cm-1; TEM data confirmed the spherical shape, smallest size of particle as 18.99 nm, while EDX analysis confirmed the elemental composition of AgNPs with 22.24% Ag. The XRD pattern confirmed the nature of AgNPs as crystalline, and zeta potential peak was found at -24.6 mV indicating the higher stability. The AgNPs exhibited increased antimicrobial activity with increase in dosage volume and considerable MIC and MBC values against microbial pathogens. In the MTT cytotoxicity assay, the IC50 value of 31.41 μg/mL is obtained against A549 cell line, suggesting the potential of AgNPs to inhibit the tumour cells; and ROS assay displayed increased ROS production with increase in treatment time. Based on the results, it is evident that Streptomyces hirsutus strain SNPGA-8 AgNPs are potentially promising to be applied for biomedical uses.

Metal Nanoparticles as Novel Antifungal Agents for Sustainable Agriculture: Current Advances and Future Directions

The use of metal nanoparticles is considered a good alternative to control phytopathogenic fungi in agriculture. To date, numerous metal nanoparticles (e.g., Ag, Cu, Se, Ni, Mg, and Fe) have been synthesized and used as potential antifungal agents. Therefore, this proposal presents a critical and detailed review of the use of these nanoparticles to control phytopathogenic fungi. Ag nanoparticles have been the most investigated nanoparticles due to their good antifungal activities, followed by Cu nanoparticles. It was also found that other metal nanoparticles have been investigated as antifungal agents, such as Se, Ni, Mg, Pd, and Fe, showing prominent results. Different synthesis methods have been used to produce these nanoparticles with different shapes and sizes, which have shown outstanding antifungal activities. This review shows the success of the use of metal nanoparticles to control phytopathogenic fungi in agriculture.

Identification and biological characterization of a new pathogen that causes potato scab in Gansu Province, China

Potato scab caused by pathogenic Streptomyces is a serious soil-borne disease on potato. In this study, a new Streptomyces strain 5A-1 was isolated from potato samples in China. Based on morphological characteristics, 16S rDNA gene sequence analyses, it was identified as Streptomyces griseoplanus (Streptacidiphilus griseoplanus), pathogenicity of which was measured by the methods of small potato chips, radish slices and potato pot trial inoculation. Moreover, the pathogenic genes txtAB and tomA from the Streptomyces pathogenicity island (PAI) were detected. Determination of biological characteristics showed that the optimal temperature for the growth of S. griseoplanus strain 5A-1 was 25 °C, the optimal light condition was darkness, the optimal pH value was 8.5 and the most preferred carbon source and nitrogen source is glucose and aspartate, respectively. To our knowledge, it is the first report for S. griseoplanus, as a new pathogen, to cause potato scab.

Bioinspired Nanomodification Strategies: Moving from Chemical-Based Agrosystems to Sustainable Agriculture

Agrochemicals have supported the development of the agricultural economy and national population over the past century. However, excessive applications of agrochemicals pose threats to the environment and human health. In the last decades, nanoparticles (NPs) have been a hot topic in many fields, especially in agriculture, because of their physicochemical properties. Nevertheless, the prevalent methods for fabricating NPs are uneconomical and involve toxic reagents, hindering their extensive applications in the agricultural sector. In contrast, inspired by biological exemplifications from microbes and plants, their extract and biomass can act as a reducing and capping agent to form NPs without any toxic reagents. NPs synthesized through these bioinspired routes are cost-effective, ecofriendly, and high performing. With the development of nanotechnology, biosynthetic NPs (bioNPs) have been proven to be a substitute strategy for agrochemicals and traditional NPs in heavy-metal remediation of soil, promotion of plant growth, and management of plant disease with less toxicity and higher performance. Therefore, bioinspired synthesis of NPs will be an inevitable trend for sustainable development in agricultural fields. This critical review will demonstrate the bioinspired synthesis of NPs and discuss the influence of bioNPs on agricultural soil, crop growth, and crop diseases compared to chemical NPs or agrochemicals.

Gold and silver nanoparticles: Green synthesis, microbes, mechanism, factors, plant disease management and environmental risks

Metal nanoparticles were being used in different processes of developmental sectors like agriculture, industry, medical and pharmaceuticals. Nano-biotechnology along with sustainable organic chemistry has immense potential to reproduce innovative and key components of the systems to support surrounding environment, human health, and industry sustainably. Different unconventional methods were being used in green chemistry to synthesize gold and silver nanoparticles from various microbes. So, we reviewed different biological processes for green synthesis of metal nanoparticles. We also studied the mechanism of the synthesis process and procedures to characterize them. Some metallic nanoparticles have shown their potential to act as antimicrobial agent against plant pathogens. Here, we outlined green nanoparticles synthesized from microbes and highlighted their role against plant disease management.

Antimicrobial and In Vitro Cytotoxic Efficacy of Biogenic Silver Nanoparticles (Ag-NPs) Fabricated by Callus Extract of Solanum incanum L

The in vitro callus induction of Solanum incanum L. was executed on MS medium supplemented with different concentrations of auxin and cytokinin utilizing petioles and explants of leaves. The highest significant fresh weights from petioles and leaf explants were 4.68 and 5.13 g/jar for the medium supplemented with1.0 mg L-1 BA and 1.0 mg L-1 2,4-D. The callus extract of the leaves was used for the green synthesis of silver nanoparticles (Ag-NPs). Analytical methods used for Ag-NPs characterization were UV-vis spectroscopy, Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and Transmission Electron Microscopy (TEM). Spherical, crystallographic Ag-NPs with sizes ranging from 15 to 60nm were successfully formed. The FT-IR spectra exhibited the role of the metabolites involved in callus extract in reducing and capping Ag-NPs. The biological activities of Ag-NPs were dose-dependent. The MIC value for Staphylococcus aureus, Bacillus subtilis, and Escherichia coli was 12.5 µg mL-1, while it was 6.25 µg mL-1 for Klebsiella pneumoniae, Pseudomonas aeruginosa, and Candida albicans. The highest inhibition of phytopathogenic fungi Alternaria alternata, Fusarium oxysporum, Aspergillus niger, and Pythium ultimum was 76.3 ± 3.7, 88.9 ± 4.1, 67.8 ± 2.1, and 76.4 ± 1.0%, respectively at 200 µg mL-1. Moreover, green synthesized Ag-NPs showed cytotoxic efficacy against cancerous cell lines HepG2, MCF-7 and normal Vero cell line with IC50 values of 21.76 ± 0.56, 50.19 ± 1.71, and 129.9 ± 0.94 µg mL-1, respectively.

Green Synthesis of Metallic Nanoparticles and Their Prospective Biotechnological Applications: an Overview

The green synthesis of nanoparticles (NPs) using living cells is a promising and novelty tool in bionanotechnology. Chemical and physical methods are used to synthesize NPs; however, biological methods are preferred due to its eco-friendly, clean, safe, cost-effective, easy, and effective sources for high productivity and purity. High pressure or temperature is not required for the green synthesis of NPs, and the use of toxic and hazardous substances and the addition of external reducing, stabilizing, or capping agents are avoided. Intra- or extracellular biosynthesis of NPs can be achieved by numerous biological entities including bacteria, fungi, yeast, algae, actinomycetes, and plant extracts. Recently, numerous methods are used to increase the productivity of nanoparticles with variable size, shape, and stability. The different mechanical, optical, magnetic, and chemical properties of NPs have been related to their shape, size, surface charge, and surface area. Detection and characterization of biosynthesized NPs are conducted using different techniques such as UV-vis spectroscopy, FT-IR, TEM, SEM, AFM, DLS, XRD, zeta potential analyses, etc. NPs synthesized by the green approach can be incorporated into different biotechnological fields as antimicrobial, antitumor, and antioxidant agents; as a control for phytopathogens; and as bioremediative factors, and they are also used in the food and textile industries, in smart agriculture, and in wastewater treatment. This review will address biological entities that can be used for the green synthesis of NPs and their prospects for biotechnological applications.

Bactericidal and In-Vitro Cytotoxic Efficacy of Silver Nanoparticles (Ag-NPs) Fabricated by Endophytic Actinomycetes and Their Use as Coating for the Textile Fabrics

An endophytic strain of Streptomyces antimycoticus L-1 was isolated from healthy medicinal plant leaves of Mentha longifolia L. and used for the green synthesis of silver nanoparticles (Ag-NPs), through the use of secreted enzymes and proteins. UV-vis spectroscopy, Fourier-transform infrared (FT-IR), transmission electron microscopy (TEM), X-ray diffraction (XRD), and dynamic light scattering (DLS) analyses of the Ag-NPs were carried out. The XRD, TEM, and FT-IR analysis results demonstrated the successful biosynthesis of crystalline, spherical Ag-NPs with a particle size of 13-40 nm. Further, the stability of the Ag-NPs was assessed by detecting the surface Plasmon resonance (SPR) at 415 nm for one month or by measuring the NPs surface charge (-19.2 mV) by zeta potential analysis (ζ). The green-synthesized Ag-NPs exhibited broad-spectrum antibacterial activity at different concentrations (6.25-100 ppm) against the pathogens Staphylococcus aureus, Bacillus subtilis Pseudomonas aeruginosa, Escherichia coli, and Salmonella typhimurium with a clear inhibition zone ranging from (9.5 ± 0.4) nm to (21.7 ± 1.0) mm. Furthermore, the green-synthesized Ag-NPs displayed high efficacy against the Caco-2 cancerous cell line (the half maximal inhibitory concentration (IC₅₀) = 5.7 ± 0.2 ppm). With respect to antibacterial and in-vitro cytotoxicity analyses, the Ag-NPs concentration of 100 ppm was selected as a safe dose for loading onto cotton fabrics. The scanning electron microscopy connected with energy-dispersive X-ray spectroscopy (SEM-EDX) for the nano-finished fabrics showed the distribution of Ag-NPs as 2% of the total fabric elements. Moreover, the nano-finished fabrics exhibited more activity against pathogenic Gram-positive and Gram-negative bacteria, even after 10 washing cycles, indicating the stability of the treated fabrics.

Hetta H, Shaheen TI. Endophytic Streptomyces laurentii Mediated Green Synthesis of Ag-NPs with Antibacterial and Anticancer Properties for Developing Functional Textile Fabric Properties

Improvement of the medical textile industry has received more attention recently, especially with widespread of microbial and viral infections. Medical textiles with new properties, such as bacterial pathogens self-cleaning, have been explored with nanotechnology. In this study, an endophytic actinomycetes strain of Streptomyces laurentii R-1 was isolated from the roots of the medicinal plant Achillea fragrantissima. This is used as a catalyst for the mediated biosynthesis of silver nanoparticles (Ag-NPs) for applications in the textile industry. The biosynthesized Ag-NPs were characterized using UV-vis spectroscopy, Fourier transform infrared (FT-IR), transmission electron microscopy (TEM), and X-ray Diffraction (XRD), which confirmed the successful formation of crystalline, spherical metal nanoparticles. The biosynthesized Ag-NPs exhibited broad-spectrum antibacterial activity. Our data elucidated that the biosynthesized Ag-NPs had a highly cytotoxic effect against the cancerous caco-2 cell line. The selected safe dose of Ag-NPs for loading on cotton fabrics was 100 ppm, regarding their antibacterial activity and safe cytotoxic efficacy. Interestingly, scanning electron microscope connected with energy dispersive X-ray spectroscopy (SEM-EDX) of loaded cotton fabrics demonstrated the smooth distribution of Ag-NPs on treated fabrics. The obtained results highlighted the broad-spectrum activity of nano-finished fabrics against pathogenic bacteria, even after 5 and 10 washing cycles. This study contributes a suitable guide for the performance of green synthesized NPs for utilization in different biotechnological sectors.

Antimicrobial, Antioxidant and Larvicidal Activities of Spherical Silver Nanoparticles Synthesized by Endophytic Streptomyces spp

In this study, metabolites involved in the free-biomass filtrates for three endophytic actinomycetes of Streptomyces capillispiralis Ca-1, Streptomyces zaomyceticus Oc-5, and Streptomyces pseudogriseolus Acv-11 were used as biocatalysts for green synthesis of silver nanoparticles (Ag-NPs). Characterization of biosynthesized Ag-NPs was accomplished using UV-Vis spectroscopy, X-ray diffraction patterns (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM-EDX), transmission electron microscopy (TEM), and particle size analyzer. The biosynthesized Ag-NPs showed maximum surface plasmon resonance (SPR) at 440 for strain Ca-1 and 450 for both strains of OC-5 and Acv-11. Nanoparticle spherical shape was recorded with size ranging from 23.77 to 63.14 nm, 11.32 to 36.72 nm, and 11.70 to 44.73 nm for Ca-1, Oc-5, and Acv-11, respectively. SEM-EDX analysis exhibited the weight percentages of 17.3, 22.3, and 48.7% for Ag-NPs synthesized by strains Ca-1, Oc-5 and Acv-11, respectively. The activities of biosynthesized Ag-NPs were concentration dependent and the obtained results confirmed the efficacy of Ag-NPs as antimicrobial agents against Gram-positive and Gram-negative bacteria as well unicellular and multicellular fungi. The MIC for Gram-positive bacteria, Gram-negative bacteria (E. coli), and eukaryotic microorganisms was 0.25 mM with clear zone ranging from 10.3 to 14.6 mm, while MIC for Pseudomonas aeruginosa was 1.0 mM for Ag-NPs synthesized by strain Ca-1 and 0.25 mM for those synthesized by strains Oc-5 and Acv-11. Moreover, Ag-NPs exhibited antimicrobial activity against four plant pathogenic fungi represented by Alternaria alternata, Fusarium oxysporum, Pythium ultimum, and Aspergillus niger at 2.0, 1.5, 1.0, and 0.5 mM of Ag-NPs with different degree. In vitro assessment of the antioxidant efficacy of biosynthesized Ag-NPs was achieved by scavenging assay of H₂O₂, reducing power of Fe³⁺, or total antioxidant assay. The results showed that antioxidant activities of Ag-NPs were concentration dependent with the highest activity at Ag-NP concentration of 2.0 mM. Furthermore, the biosynthesized NPs have prospective bioinsecticidal activity against Culex pipiens and Musca domestica. Green synthesis of NPs could be quite potential for the development of new bioactive compounds used in different biomedical applications.

Multifunctional properties of spherical silver nanoparticles fabricated by different microbial taxa

This study addresses the impacts of metabolites from different microbial taxa on the fabrication and multifunctional biological properties of spherical silver nanoparticles (Ag-NPs). Three microbial taxa, a bacterial (Bacillus cereus A1-5), actinomycetes (Streptomyces noursei H1-1), and fungal (Rhizopus stolonifer A6-2) strains were used for Ag-NPs biosynthesis, whereas Streptomyces noursei is demonstrated for the first time. These isolates were identified using either 16S rRNA or ITS gene sequencing. Characterization of Ag-NPs was done using color change analysis, Uv-Vis spectroscopy, FT-IR spectroscopy, XRD, TEM, SEM-EDX, DLS, and Zeta potential analysis. All biosynthesized NPs exhibited spherical shape with different sizes ranged from 6‒50 nm, 6-30 nm and 6-40 nm for NPs obtained by A1-5, H1-1 and A6-2, respectively. The crystalline center cubic face of Ag-NPs was confirmed using XRD at 2θ values 38.08o, 44.27o, 64.41o and 77.36o. FT-IR analysis revealed varied intense absorption peaks for biomolecules required for NPs synthesize by each microbial strain. The stability of spherical Ag-NPs was confirmed due to highly DLS negative surface charge of ‒17.5mV, ‒18.9mV, and ‒15.6mV for NPs synthesized by strains A1-5, H1-1, and A6-2, respectively. Ag-NPs exhibited a broadspectrum of antibacterial activity against Gram-positive and Gram-negative bacteria with varied effectiveness. They also exhibited a cytotoxic effect against cancer cell line (caco-2) in a dose-dependent pattern with IC50 of 8.9 ± 0.5, 5.6 ± 3.0, 11.2 ± 0.5 μg/ml for NPs synthesized by strains A1-5, H1-1, and A6-2, respectively. Moreover, these spherical Ag-NPs showed larvicidal activity against the 3rd instar larvae of the dengue vector Aedes aegypti.

Nanoparticles from Actinobacteria: A Potential Target to Antimicrobial Therapy

Nanoparticles have gained significant importance in the past two decades, due to their multifaceted applications in the field of nanomedicine. As our ecosystems and habitats are changing due to global warming, many new diseases are emerging continuously. Treating these costs a lot of money and mostly ends up in failure. In addition, frequent use of antibiotics to control the emerging diseases has led the pathogens to develop resistance to antibiotics. Hence, the nanoparticles are targeted to treat such diseases instead of the costly antibiotics. In particular, the biosynthesized nanoparticles have received considerable attention due to their simple, eco-friendly and promising activity. To highlight, microbial mediated nanoparticles have been found to possess higher activity and thus have a promising role in antimicrobial therapy to fight against the emerging drug-resistant pathogens. In this context, this review article is aimed at highlight the role of nanoparticles in the field of nanomedicine and importance of actinobacteria in the nanoparticle synthesis and their need in antimicrobial therapy. This is a comprehensive review, focusing on the potential of actinobacteria-mediated nanoparticles in the field of nanomedicine.

Biosynthesis of Metal Nanoparticles via Microbial Enzymes: A Mechanistic Approach

During the last decade, metal nanoparticles (MtNPs) have gained immense popularity due to their characteristic physicochemical properties, as well as containing antimicrobial, anti-cancer, catalyzing, optical, electronic and magnetic properties. Primarily, these MtNPs have been synthesized through different physical and chemical methods. However, these conventional methods have various drawbacks, such as high energy consumption, high cost and the involvement of toxic chemical substances. Microbial flora has provided an alternative platform for the biological synthesis of MtNPs in an eco-friendly and cost effective way. In this article we have focused on various microorganisms used for the synthesis of different MtNPs. We also have elaborated on the intracellular and extracellular mechanisms of MtNP synthesis in microorganisms, and have highlighted their advantages along with their challenges. Moreover, due to several advantages over chemically synthesized nanoparticles, the microbial MtNPs, with their exclusive and dynamic characteristics, can be used in different sectors like the agriculture, medicine, cosmetics and biotechnology industries in the near future.