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Gold nanoparticles have received considerable attention in recent years because of their promising applications in diagnostic imaging, biosensors, biolabels, and drug and gene delivery systems. The chemical methods of nanoparticle synthesis are the most widely and traditionally used methods. Production of nanoparticles by chemical methods causes contamination from precursor chemicals due to the use of toxic solvents and generation of hazardous by-products. On the other hand, the physical methods have low yield and high cost. Hence, there is an increasing need to develop low cost, non-toxic, biocompatible and environmentally benign processes for synthesis of metallic nanoparticles where the biological approaches for synthesis of nanoparticles gain importance. In this study, we investigated the biosynthesis of gold nanoparticles using Streptomyces sp. ERI-3. Streptomycessp.ERI-3 was isolated from the soil of Ahar Copper Mine (Ahar, Iran) and its biomass was incubated at 28ºC on a rotary shaker (200 rpm) for 48 h. The nanoparticles were characterized by means of UV-vis spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM).The nanoparticles exhibited maximum absorbance at 540 nm (special wavelength of gold nanoparticles) in UV-vis spectroscopy. The XRD spectrum of gold nanoparticles exhibited 2Ө values corresponding to the gold nanocrystals. The TEM micrographs revealed the extracellular and attached to cell surface formation of gold nanoparticles in the size range of 50-100 nm with spherical morphology.  

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In biological methods, microorganisms such as bacteria, fungi, actinomycets and yeasts are used to produce metal nanoparticles. Fungi are extremely good candidates in the synthesis of silver nanoparticles because of their ability to secrete large amounts of enzymes. The aim of this study was the biosynthesis of silver nanoparticles by Penicillium spp. isolated from the soil of plump and zinc mine in Zanjan city (Iran). After culturing, growth of colonies and isolation of Penicillium spp., 15 g of the fungal biomass was mixed into 1 mM silver solution for 72 h incubation. The production of silver nanoparticles was characterized by UV-vis spectroscopy, X-ray diffraction(XRD) and transmission electron microscopy. Among the sixteen kinds of isolated fungi, six species were recognized as Penicillium of which just the fungus Penicilliumbrevicompactum was found to be able to produce silver nanoparticles. The production of silver nanoparticles was preliminarily approved by observing  the color change of the reaction solution from colorless to yellowish brown. The synthesis of silver nanoparticles was confirmed by observing the characteristic peak at 406-425 nm. The presence of crystalline silver nanoparticles was confirmed by observing peaks in (111), (200), (220), (311) in the XRD  analysis. Transmission electron microscopy images showed that silver nanoparticles were produced in the size range of 50 -100 nm in spherical shape mainly extracellular at the surface of mycelium. The fungus was recognized to be Penicilliumbrevicompactumusing slide culture method, growth on Czapek yeast agar and Keratin-sucrose agar.

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Nanotechnology involves technological research and development in spaces at the range of 1 to 100 nanometers, and in this technology, very small and atomic scale particles are created and handled. Plant extracts can be used as a green method for the synthesis of silver nanoparticles. In this study, the biosynthesis of silver nanoparticles was performed using extracts of sesame (Sesamum indicum) seeds. Silver nitrate was added to the seed extract, and then it was incubated at 30 ° C. The effects of three concentrations (1mM, 2mM and 3mM) of silver nitrate on the synthesis of silver nanoparticles were studied. The analyses of absorption spectroscopy UV-Visible, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD) and Inductively Coupled Plasma (ICP) were conducted to assess the production of nanoparticles. UV-Visible spectroscopy analysis and the peak at 420 nm indicated the occurrence of nanoparticles in the extract. TEM image determined that the nanoparticles were spherical with average size of about 14 nm. XRD analysis showed the nano-crystals synthesized by the extract, and Inductively coupled Plasma (ICP) determined the conversion percentage of silver ion into silver nanoparticle as approximately 99.61 percent.

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Diatoms biosilica shell, frustule, is substitute biostructures to mesoporous silica particles, which possesses their wide surfaces, nano-diameter porosity, mechanical strength, and thermal stability, optical capabilities, and the ability to bind to biomolecules can be used in biosensing applications. In this study, diatom species called Chaetoceros muelleri, was used for the fabrication of the Fe₂O₃-Au-Biosilica magnetic package. After micro-algae cultivation, the synthesis of gold nanoparticles (AuNPs) on silica walls was carried out using the bio-synthesis method, which evaluations have demonstrated the continuous formation of spherical AuNPs on the walls and its surfaces. After this step, the magnetic iron oxide nanoparticles were attached to the silica surface of the diatom, this, in turn, leads to system guiding using a magnetic field. Surface modification of diatoms magnetic complex, by using the APTES, allowed the attachment of fluorescence Rhodamine and the Herceptin antibody (Trastuzumab) to the structure. As well as the attachment of the fabricated system to target cells (SKBR3) was confirmed by fluorescence microscopic analysis. The results of this study indicate the ability and specificity of the diatom silicone shell as a "multipurpose" package for diagnostic and therapeutic activities.

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Today, nanosilver is one of the most commercialized nanomaterials. The demand for synthesis of Nanosilver through biocompatible routs due to wide biomedical application has increased. Use of plants and plant products as sustainable and renewable resources in the synthesis of nanoparticles is more advantageous over other biological routes. In this study, biosynthesis of silver nanoparticles (AgNPs) using aqueous extract of Withania somnifera as reducing agent is reported. Effect of parameters such as AgNO3 concentration, aqueous extract, pH and formation time were investigated and optimized by UV-visible spectroscopy in the synthesis of nanoparticles. At room temperature, the solution color started to change from pale yellow to dark brown due to the reduction of silver ion. The transmission electron microscopy (TEM) was applied for size and morphological analysis of nanoparticles. TEM result shows a spherical structure with an average size ranging from 24-35 nm for silver nanoparticles.
 

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In stevia (Stevia rebaudiana), breeding programs are mainly aimed at developing plants with high Rebaudioside-A (RA) content. To this end, in order to screen stevia plants and selection of varieties with the highest amount of desired sweeteners (RA) using molecular markers, the present study was conducted on RNA-seq data of varieties having different amounts of RA. We took advantage of CLC to make de novo transcriptome assembly for each variety with k-mer and contig length values of 20 and 200bp, respectively. The assembly was annotated using the latest Arabidopsis proteome release. To identify signatures of candidate polymorphic SSRs among the stevia varieties, the assembled sequences were used as an input for CandiSSR, followed by designing primer pairs for identified polymorphic SSRs. We identified 368 potential polymorphic SSRs based on the stevia transcriptome analysis, among which 360 were qualified for primer design. Almost 89% of the contig sequences possessing polymorphic SSRs had the best blast hit against Arabidopsis proteome. We found contigs similar to the UDP-Glycosyltransferase protein family and Deoxyxylulose-5-phosphate synthase which are involved in biosynthesis pathway of steviol glycosides. Also, gene set enrichment analysis using PlantGSE through Hypergeometric test (FDR<0.05) identified enriched metabolic pathways in the sequences contained polymorphic SSRs; It is therefore most likely that such connections exist between the SSRs and biosynthesis of steviol glycosides. Hence, it could conceivably be hypothesized that the SSR markers developed in this study would be reliable in molecular breeding of stevia toward selection of varieties with high RA content.

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Among rhizobacteria, plant-beneficial effects of Pseudomonas bacteria are known in agricultural ecosystems. Screening of fluorescent pseudomonad isolates obtained from potato rhizosphere led to selecting five bio-reagents capable of controlling soft rot disease caused by Pectobacterium carotovorum subsp. carotovorum (Pcc) (JX029052) in plate assay, on intact potato tubers and under storage challenges using preventative and curative applications. The biocontrol features related to the tested rhizospheric bacteria were also evaluated. According to phenotypic tests, the representative antagonistic strains belong to the fluorescent pseudomonads group and are placed in the P. protegens cluster based on 16S rRNA gene sequencing. Strains IrPs8 and IrPs18 are potent to produce siderophore, cyanide hydrogen, and protease, form strong biofilm and carry phl, plt and prn genes on their genomes corresponding to 2, 4-diacetylphloroglucinol, pyoluteorin and pyrrolnitrin, respectively. Treated tubers inoculated with IrPs8 and IrPs18 showed a reduction in the soft rot-inducing potency of Pcc by 63.4 and 65.5% in preventative and by 57.8 and 58.3% in curative tests, respectively, under storage conditions that confirmed the in vivo results. This study highlights the potential of rhizospheric P. protegens strains as beneficial bacteria that can be suggested as preservative coatings for potato tubers under storage conditions.

 

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Aspartic proteases play a vital role in diverse biological processes, with microbial variants garnering considerable attention for their commercial potential across various industries. This comprehensive review delves into the intricate aspects of microbial aspartic proteases, encompassing their biosynthesis, genetic regulation, secretion mechanisms, post-translational modifications, characteristics, and emerging applications. The biosynthesis of these proteases involves the translation of corresponding genes into precursor proteins, which undergo a series of processing steps culminating in the formation of mature enzymes. The efficiency of aspartic protease production and commercialization relies heavily on understanding the mechanisms governing their secretion. Notably, post-translational modifications, such as glycosylation and phosphorylation, play a significant role in influencing the activity and stability of these enzymes. The review further explores the substrate specificity and catalytic properties of microbial aspartic proteases, along with their potential applications in the food industry, pharmaceuticals, and biotechnology sectors. In the food industry, these proteases find utility in enhancing flavor, texture, and nutritional value. In the pharmaceutical realm, they contribute to drug discovery and development. Additionally, in biotechnology, microbial aspartic proteases exhibit versatility in applications such as protein engineering, peptide synthesis, and bioremediation. This comprehensive examination provides valuable insights into the multifaceted nature of these enzymes, shedding light on their biosynthesis, genetic regulation, secretion mechanisms, post-translational modifications, characteristics, and promising commercial applications.
 

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Fire blight, caused by Erwinia amylovora bacteria, is one of the well-known plant diseases in the world including major diseases of the fruit trees, especially apples and pears. In recent years, due to chemical nature of the pesticides damaging human health and environment, the importance of biological control is considered as alternative measure to manage plant diseases. To investigate the possibility of biological control of the pathogens, healthy foliar samples of apple, pear, and quince trees were collected from different regions of Kerman Province, Iran, and then, biocontrol activity of antagonist agents was evaluated under laboratory conditions. On the basis of the results, some of the antagonists could decrease the symptoms of the disease by 14.28-79.59%. Laboratory evaluation included investigating the disease severity in immature pears, biocontrol activity of antagonist agents in the plate assay, inhibitory siderophore production, biofilm formation capacity, drought stress tolerance, and silver nanoparticle synthesis capability, which showed that these antagonist agents could potentially control the disease. Among the 9 well-performed antagonistic isolates from apples and pears, Vr87 isolate was selected. The studies were confirmed by amplifying part of 16S rDNA region of the isolate, using specific primers. By comparing the results on the NCBI website, the selected isolate was identified as Enterobacter sp. genus. Among all selected isolates as successful factors in controlling fire blight pathogen, including isolated isolates and isolates in the collection of Vali-e-Asr University, Bacillus subtilis strain BsVRU1 in the Vali-e-Asr University collection, with 73.5% inhibition, had higher inhibitory power than the other antagonist isolates against the pathogen of fire blight disease.

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Introduction: Today, the biosynthesis of nanoparticles (NPs) assisted by microorganisms (particularly bacteria) received increasing attention. In this study, Bacillus subtilis strain SFTS, a bismuth-reducing bacterium, was isolated from the soil of a copper mine in the South of Iran and used for biosynthesis of bismuth NPs (Bi NPs).
Materials and methods: Bacillus subtilis strain SFTS was identified by conventional identification tests and the 16S rDNA fragment amplification method. Characterizations of the bio-fabricated Bi NPs were examined using FTIR, EDS, XRD, TEM, and SEM analysis after purification of Bi NPs. In addition, the synergistic effect of biogenic Bi NPs in combination with different antibiotics was also investigated.
Results: The attained results revealed that the biosynthesized Bi NPs average size was 22.36 nm and spherical in shape. The XRD pattern showed that the biosynthesized nanoparticles consisted only of Bi₄ and monoclinic crystals. Furthermore, the results of antibacterial effect of Bi NPs in combination with various antibiotics showed that the nanoparticles represented the highest synergistic effect together with imipenem and the lowest effect in combination with tetracycline against clinical strains of E. coli and K. pneumoniae. Significant difference between synergistic effect of Bi NPs with antibiotics compared to antibiotics disc alone against E. coli and K. pneumoniae strains was observed (P<0.001).
Conclusion: This study showed that Bi NPs biologically synthesized by Bacillus subtilis strain SFTS had a small size and different structure. However, finding about their antibacterial effect and related mechanism merit further investigations.