Mosquitoes represent a considerable risk to human health due to their role in transmitting various pathogens responsible for diseases like chikungunya, malaria, dengue, and Japanese encephalitis. There is an immediate necessity to explore innovative biological strategies to combat mosquito-borne illnesses. One promising avenue in current research is the development of bioinsecticides utilizing advanced nanotechnology. Therefore, this study aimed to synthesize silver nanoparticles from the actinobacterial strain Streptomyces anthocyanicus (OR186732), isolated from the Western Ghats in Tamil Nadu, India. The AgNPs were synthesized and then characterized using UV-visible spectroscopy, identifying a prominent absorption peak at 424 nm. The identification of different functional groups within the AgNPs was confirmed through FTIR. The produced AgNPs were shown to be crystalline by XRD analysis. The nanoparticles were characterized using FESEM, HRTEM, and EDX to analyze their morphology, size, and elemental composition. The stability was assessed through Zeta potential measurements, which were measured at -0.2 mV. The synthesized AgNPs showed strong larvicidal effects against Culex quinquefasciatus (LC50 = 2.924 ppm), Aedes aegypti (LC50 = 3.245 ppm), and Anopheles stephensi (LC50 = 3.767 ppm). Furthermore, the AgNPs were observed to significantly increase the levels of antioxidant enzymes such as SOD and GPx at high concentrations. In contrast, levels of detoxifying enzymes such as AChE and GST levels were reduced. Histological analysis of mosquito larvae treated with AgNPs revealed significant damage to the midgut tissues. The research suggests that AgNPs synthesized by Actinobacteria could be an environmentally friendly option for biological mosquito control.

BackgroundTomato yield is significantly reduced by root-knot nematodes (RKN; Meloidogyne spp.), particularly in tropical and subtropical regions. This study evaluated 20 bacterial isolates (B1-B20), belonging to the genera Bacillus, Lysobacter, Paenibacillus, and Streptomyces, from Sekem farms in Egypt for their potential to biocontrol RKN and stimulate plant growth in tomato 'Moneymaker.' The bacteria were compared to well-known microbial biocontrol agents (MBA), including Rhizobium etli G12 (B21), Pseudomonas trivialis 3Re2-7 (B22), Sporosarcina psychrophile Sd4-11 (B23), and B. subtilis Sb1-20 (B24), and a negative control, Escherichia coli JM109 (B25). The study involved seed-coated and -uncoated plants with bacterial isolates, planted in plastic pots, and inoculated with 1500 M. incognita J2 individuals per pot. Plants were grown in a saran-house during the 2022 and 2023 fall seasons, and their RKN-satisfying response (number of galls: NG and egg masses: NEM), vegetative growth, and metabolic activity were assessed 45 days after inoculation.ResultsIn seasons of 2022 and 2023, seed coating with bacterial isolates achieved a significant improvement in plant growth (coefficient of variation: CV ranging 26.8-120.2% in 2022 and 10.9-48.8% in 2023) and a reduction in RKN-satisfying response (CV for NG: 57.6 and 53.8%, respectively; and for NEM: 56.5 and 65.3%, respectively). Compared to uncoated-seed plants, the bacterial seed coating reduced NG by 0.66-74.09% in 2022 and 14.61-66.29% in 2023. Similarly, NEM decreased by 0.63-70.61% in 2022 and 41.91-77.46% in 2023. The coated-seed plants by Bacillus subtilis subsp. spizizenii (B5), Streptomyces subrutilus Wb2n-11 (B12), Streptomyces scabiei (B19), and Bacillus mojavensis (B20), along with the well-known MBAs B22 and B23, showed increased photosynthetic pigments, fresh weight of roots and shoots, stem size, and number of leaves. This growth has also led to higher dry weights in roots and shoots, and an increase in the root content of carbohydrates and proteins. Seed coating induced systemic RKN resistance by increasing polyphenols in the root. In contrast, uncoated-seed plants showed reduced foliar photosynthesis pigment and metabolic activity due to high RKN damage. Principal component analysis revealed significant correlations among the evaluated traits. Hierarchical clustering categorized bacteria isolates into five clusters based on their impact on estimated plant traits.ConclusionB5, B12, B19, B20, B22, and B23 demonstrated superior performance in both controlling RKN and stimulating vegetative growth in tomato 'Moneymaker' plants as known MBAs.

Kiwifruit soft rot is a disease caused by fungal pathogens such as Botryosphaeria dothidea, which considerably restricts the development of kiwifruit industry. To provide novel management strategies against kiwifruit soft rot disease, potential biocontrol actinomycete strains were isolated from kiwifruit rhizosphere soil. A total of 21 actinomycete strains were obtained and strain SC-3 exhibited the highest biocontrol activity against B. dothidea. Based on the morphological, biochemical and molecular characteristics strain SC-3 was identified as Streptomyces albidoflavus. The SC-3 and its aseptic filtrate (AF) exhibited excellent antifungal activities against 11 tested pathogenic fungi. AF displayed antifungal effects through suppressing mycelial growth, spore germination, and the pathogenicity of B. dothidea. Electron microscopy analysis revealed that AF could cause significant alterations on ultrastructure of B. dothidea. Moreover, AF severely damaged cell membrane integrity, resulting in the leakage of cellular components in B. dothidea. Metabolomic analyses of SC-3 AF revealed the presence of several important antifungal compounds in the AF such as antimycin, and candicidin. Correspondingly, the whole genome analyses of SC-3 identified gene clusters responsible for the biosynthesis of these compounds. Overall, SC-3 is a potential biological control agent against B. dothidea and other fungal phytopathogens.

Fifteen new aliphatic metabolites, 2-methylpyrimidin-4(3H)-ones (1,2), 2-methoxy-2-methyl-1,2-dihydro-3Hpyrrol-3-ones (4a/4b, 5a/5b), butyrolactones (6-9), and aliphatic metabolites (16-20) as well as known pyridin2(1H)-one (3) and butyrolactone analogues (10-15) were obtained from the fermentation broth of Streptomyces antifungus isolated from the forest soil sample collected in Tengchong, China. Pyrimidin-4(3H)-one derivatives (1, 2) with an individual 2-methylpyrimidin-4(3H)-one skeleton is a kind of rarely reported compound and were firstly obtained from natural source. The structures of the new metabolites were elucidated by comprehensive spectroscopic analysis including data from experimental and calculated ECD spectra as well as Mosher's reagent derivative method. Compounds 1, 2, 18, and 19 exhibited optimal activity against Staphylococcus aureus with MIC values ranged from 12.5 to 50 mu g/mL. Further investigation revealed that 1 effectively inhibited biofilm formation and destroyed the preformed biofilm of S. aureus through oxidative damage, thereby exerting antibacterial effect.

Pythium irregulare (P. irregulare) is one of the soil-borne pathogens that is the primary cause of damage to several plants each year. The novelty and originality of this work were the ability of Streptomyces gancidicus (S. gancidicus OR229936) to synthesize bimetallic zinc oxide-boron oxide nanoparticles (ZnO-B2O3 NPs) for reducing P. irregulare growth and safeguarding pea plant from damping off disease. The produced bimetallic ZnO-B2O3 NPs' XRD results highlighted the ZnO diffraction peaks at 2 = 27.50 degrees, 31.15 degrees, 45.15 degrees, 56.89 degrees, 67.98 degrees, and 75.25 degrees, which are complemented by the standard card JCPDS number 361451 and correspond to (002), (101), (102), (110), (103), and (201) Bragg's reflections. Along with the standard card JCPDS number 300019, they additionally include the B2O3 NP diffraction peaks at 2 = 15.25 degrees, 28.69 degrees, 31.99 degrees, and 41.28 degrees. Bimetallic ZnO-B2O3 NPs were tested against P. irregular for their antifungal activities. The findings indicated that ZnO-B2O3 NPs exhibited potential anti P. irregulare activity, with an inhibition zone of 33 mm at a concentration of 1000 mu g/mL and a promising MIC of 0.01 mu g/mL. Bimetallic ZnO-B2O3 NPs (0.01 ppm) application appeared to significantly lessen the severity of the pea post-emergence damaging off disease by 10% and to provide significant protection by 88%. In comparison to fungicide (difenoconazole 25%) treatments, all metabolic resistance indicators significantly enhanced after the usage of bimetallic ZnO-B2O3 NPs, ZnO NPs, and B2O3 NPs with ethyl acetate extract of S. gancidicus. The beneficial impacts of the bimetallic ZnO-B2O3 NPs, ZnO NPs, and B2O3 NPs have been broadened to increase the enzyme activities of peroxidase (POD) and polyphenol oxidase (PPO) in both healthy and infected pea plant in comparison to control. Reduction of Malondialdehyde content (MDA) in response to S. gancidius filtrate, bimetallic ZnO-B2O3 NPs, ZnO NPs, B2O3 NPs, and difenoconazole by 41.68%, 36.51%, 26.15, 26.15, and 15.25%, respectively. Also, contents of H2O2 in infected pea plant were diminished by 50%, 45%, 40%, 37.5%, and 22.5% at bimetallic ZnO-B2O3 NPs, S. gancidicus filtrate, ZnO NPs, difenoconazole, and B2O3 NPs comparing to P. irregular-infected pea plant is strong evidence to induce disease recovery. The application of bimetallic ZnO-B2O3 NPs seems to be a significant approach to relieve the toxic influences of P. irregulare on infected pea plant as green and alternative therapeutic nutrients of chemical fungicides.

A novel actinomycete, strain 1_25(T), was isolated from soil under a black Gobi rock sample from Shuangta, PR China, and characterized using a polyphasic taxonomic approach. The results of comparative analysis of the 16S rRNA gene sequences indicated the 1_25(T) represented a member of the genus Streptomyces. Chemotaxonomic data revealed that 1_25(T) possessed MK-9(H-8) as the major menaquinone. The cell wall contained LL-diaminopimelic acid (LL-DAP) and the whole-cell sugar pattern consisted of ribose, glucose and galactose. Major fatty acid methyl esters were observed to be iso-C-16:0 (23.6%), and anteiso-C-15:0 (10.4%). The genomic DNA G+C content of 1_25(T) was 69 mol%. The results of phylogenetic analysis based on 16S rRNA gene sequence indicated that 1_25(T) had high sequence similarity with Streptomyces qinglanensis 172205(T) (98.1%), Streptomyces lycii TRM 66187(T) (98 %), and Streptomyces griseocarneus JCM4580(T) (98 %). In addition to the differences in phenotypic characters, the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between 1_25(T) and closely related species were below the recommended threshold values for assigning strains to the same species. The fermentation product of 1_25(T) in ISP2 had an inhibitory effect on Staphylococcus aureus. On the basis of these genotypic and phenotypic characteristics, strain 1_25(T) (=JCM 34936(T)=GDMCC 4.216(T)) represents a novel species of the genus Streptomyces, for which the name Streptomyces gobiensis sp. nov. is proposed.

Background Soil-borne plant diseases represent a severe problem that negatively impacts the production of food crops. Actinobacteria play a vital role in biocontrolling soil-borne fungi. Aim and objectives The target of the present study is to test the antagonistic activity of chitinase-producing Streptomyces cellulosae Actino 48 (accession number, MT573878) against Rhizoctonia solani. Subsequently, maximization of Actino 48 production using different fermentation processes in a stirred tank bioreactor. Finally, preparation of bio-friendly formulations prepared from the culture broth of Actino 48 using talc powder (TP) and bentonite in a natural as well as nano forms as carriers. Meanwhile, investigating their activities in reducing the damping-off and root rot diseases of peanut plants, infected by R. solani under greenhouse conditions. Results Actino 48 was found to be the most significant antagonistic isolate strain at p <= 0.05 and showed the highest inhibition percentage of fungal mycelium growth, which reached 97%. The results of scanning electron microscope (SEM) images analysis showed a large reduction in R. solani mycelia mass. Additionally, many aberrations changes and fungal hypha damages were found. Batch fermentation No. 2, which was performed using agitation speed of 200 rpm, achieved high chitinase activity of 0.1163 U mL- 1 min- 1 with a yield coefficient of 0.004 U mL- 1 min- 1 chitinase activity/g chitin. Nano-talc formulation of Actino 48 had more a significant effect compared to the other formulations in reducing percentages of damping-off and root rot diseases that equal to 19.05% and 4.76% with reduction percentages of 60% and 80%, respectively. The healthy survival percentage of peanut plants recorded 76.19%. Furthermore, the nano-talc formulation of Actino 48 was sufficient in increasing the dry weight of the peanut plants shoot, root systems, and the total number of peanut pods with increasing percentages of 47.62%, 55.62%, and 38.07%, respectively. Conclusion The bio-friendly formulations of actinobacteria resulting from this investigation may play an active role in managing soil-borne diseases.

The recent emergence of drug-resistant microorganisms and the prevalence of cancer diseases are both presenting substantial global public health concerns. Silver nanoparticles (AgNPs) have attracted significant attention and are increasingly employed in diverse biomedical applications as agents with antimicrobial and anticancer properties. The study herein focused on the biogenic synthesis of AgNPs employing the cell-free filtrate of the soil-derived bacterium Streptomyces pratensis as a reducing agent. AgNPs were characterized using UV-Vis, FTIR, FE-SEM, and TEM. The study assessed both the antibacterial and anticandidal modes of action, along with the potential anticancer properties of the biosynthesized AgNPs. The spherical, 17-44-nm biosynthesized AgNPs demonstrated strong antimicrobial and antibiofilm activities against pandrug-resistant (PDR) Gram-negative Klebsiella pneumoniae and pathogenic yeast Candida albicans, both of which were isolated from immunosuppressed patients. Dose-dependent interactions between the AgNPs and their anticancer activity were observed. The IC50 values of the AgNPs against the hepatocellular (HepG2) and colon carcinoma (HCT-116) cancer cell lines were approximately 16.5 mu g/mL and 11.5 mu g/mL, respectively. Furthermore, the antimicrobial mechanism of action of AgNPs revealed distinct leakage of sugar, DNA, and proteins from the cell membrane of both K. pneumoniae and C. albicans, as well as increased ROS generation. Moreover, the TEM micrographs depicted the distortion and damage experienced by the microbial cells after exposure to AgNPs. The findings of the current study suggest that biosynthesized AgNPs have the potential to serve as alternative therapeutic agents for combating drug-resistant K. pneumoniae, the yeast C. albicans, in addition to HepG2 and HCT-116 cells.

Potato common scab is a soil-borne bacterial disease caused by Streptomyces scabies, which is ubiquitous and difficult to control. In this study, the issue of developing antimicrobial agents derived from plant extracts against S. scabies was addressed. Three bioactive phenolic compounds, named gallic acid, 1-O-galloyl-beta-D-glucose, and corilagin, were isolated and identified from Phyllanthus emblica pomace through bioassay-guided fractionation. The antibacterial effects of these compounds on S. scabies were evaluated with MIC values of 0.63, 0.31, and 1.25 mg/mL, respectively. Furthermore, Structure-activity relationship analyses of 17 gallic acid and its structural analogs revealed that the R6 position of the benzene ring was a key factor to their antibacterial activity against S. scabies, among which pyrogallol had the best antibacterial effect. Scanning electron microscopy showed that when S. scabies was exposed to this gallic acid and its structural analogs, the cell membranes of which was damaged. The results will help promote the development and structural modification of plant-derived bacteriostatic agents.

Actinobacteria are abundant in soil and other environmental ecosystems and are also an important part of the human microbiota. Hence, they can also be detected in indoor environments and on building materials, where actinobacterial proliferation on damp materials can indicate moisture damage. The aim of this study was to evaluate the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for the identification of 28 environmental strains of Actinobacteria isolated from building materials and indoor and outdoor air samples, mainly collected in the context of moisture damage investigations in buildings in Finland. The 16S rRNA gene sequencing and chemotaxonomic analyses were performed, and results were compared with the MALDI-TOF MS Biotyper identification. Using 16S rRNA gene sequencing, all isolates were identified on the species or genus level and were representatives of Streptomyces, Nocardia, and Pseudonocardia genera. Based on MALDI-TOF MS analysis, initially, 11 isolates were identified as Streptomyces spp. and 1 as Nocardia carnea with a high identification score. After an upgrade in the MALDI-TOF MS in-house database and re-evaluation of mass spectra, 13 additional isolates were identified as Nocardia, Pseudonocardia, and Streptomyces. MALDI-TOF MS has the potential in environmental strain identification; however, the standard database needs to be considerably enriched by environmental Actinobacteria representatives.IMPORTANCEThe manuscript addresses the challenges in identifying environmental bacteria using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) Biotyper-based protein profiling. The matter of the studies-actinobacterial strains-has been isolated mostly from building materials that originated from a confirmed moisture-damaged situation. Polyphasic taxonomy, 16S RNA gene sequencing, and MALDI-TOF mass spectrometry were applied for identification purposes. In this experimental paper, a few important facts are highlighted. First, Actinobacteria are abundant in the natural as well as built environment, and their identification on the species and genus levels is difficult and time-consuming. Second, MALDI-TOF MS is an effective tool for identifying bacterial environmental strains, and in parallel, continuous enrichment of the proteomics mass spectral databases is necessary for proper identification. Third, the chemical approach aids in the taxonomical inquiry of Actinobacteria environmental strains. The manuscript addresses the challenges in identifying environmental bacteria using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) Biotyper-based protein profiling. The matter of the studies-actinobacterial strains-has been isolated mostly from building materials that originated from a confirmed moisture-damaged situation. Polyphasic taxonomy, 16S RNA gene sequencing, and MALDI-TOF mass spectrometry were applied for identification purposes. In this experimental paper, a few important facts are highlighted. First, Actinobacteria are abundant in the natural as well as built environment, and their identification on the species and genus levels is difficult and time-consuming. Second, MALDI-TOF MS is an effective tool for identifying bacterial environmental strains, and in parallel, continuous enrichment of the proteomics mass spectral databases is necessary for proper identification. Third, the chemical approach aids in the taxonomical inquiry of Actinobacteria environmental strains.