Gram-positive Bacteria Bacillus Subtilis Research Articles

Complex sporulation-specific expression of transcription termination factor Rho highlights its involvement in Bacillus subtilis cell differentiation

Termination factor Rho, responsible for the main factor-dependent pathway of transcription termination and the major inhibitor of antisense transcription, is an emerging regulator of various physiological processes in microorganisms. In Gram-positive bacterium Bacillus subtilis, Rho is involved in the control of cell adaptation to starvation and, in particular, in the control of sporulation, a complex differentiation program leading to formation of a highly resistant dormant spore. While the initiation of sporulation requires a decrease in Rho protein levels during the transition to stationary phase, the mechanisms regulating the expression of rho gene throughout the cell cycle remain largely unknown. Here we show that a drop in the activity of the vegetative SigA-dependent rho promoter causes the inhibition of rho expression in stationary phase. However, after the initiation of sporulation, rho gene is specifically reactivated in two compartments of the sporulating cell using distinct mechanisms. In the mother cell, rho expression occurs by read-through transcription initiated at the SigH-dependent promoter of the distal spo0F gene. In the forespore, rho gene is transcribed from the intrinsic promoter recognized by the alternative sigma factor SigF. These regulatory elements ensure the activity of Rho during sporulation, which appears important for the proper formation of spores. We provide experimental evidence that disruption of the spatiotemporal expression of rho during sporulation affects the resistance properties of spores, their morphology, and the ability to return to vegetative growth under favorable growth conditions.

In Situ Antimicrobial Properties of Sabinene Hydrate, a Secondary Plant Metabolite.

The objective of this research was to investigate natural products for their potential against pathogenic microorganisms. Sabinene hydrate (SH), a monoterpenoid, is synthesised by numerous different plants as a secondary metabolite. At present, there is a lack of definite investigations regarding the antimicrobial activity of SH itself and its different isomers. The antimicrobial effects of commercially available SH (composed mainly of trans-isomer) were evaluated within a range of concentrations in three types of contact tests: solid and vapor diffusion and the macro-broth dilution method. Moreover, the effects of SH on the rate of linear growth and spore germination were also examined. Ethanolic SH solutions were tested against an array of microorganisms, including blue-stain fungi (Ceratocystis polonica, Ophiostoma bicolor, O. penicillatum), frequently originating from bark beetle galleries; three fungal strains (Musicillium theobromae, Plectosphaerella cucumerina, and Trichoderma sp.) isolated from a sapwood underneath bark beetle galleries (Ips typographus) on spruce (Picea abies) stems; Verticillium fungicola, isolated from diseased I. typographus larvae; two Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa); five yeasts (Candida albicans, C. krusei, C. parapsilosis, Saccharomyces cerevisiae, and Rhodotorula muscilaginosa), and two saprophytic fungi (Aspergillus niger and Penicillium notatum). In solid agar disc diffusion tests, Gram-positive bacteria exhibited greater susceptibility to SH than Gram-negative bacteria, followed by yeasts and fungi. The most resistant to SH in both the disc diffusion and broth macro-dilution methods were P. aeruginosa, A. niger, and Trichoderma sp. strains. Blue-stain fungi and fungi isolated from the Picea sapwood were the most resistant among the fungal strains tested. The minimum inhibition concentrations (MICs) generated by SH and determined using a disc volatilization method were dependent on the fungal species and played an important role in the development of microorganism inhibition. The two Gram-positive bacteria, B. subtilis and S. aureus (whose MICs were 0.0312 and 0.0625 mg/mL, respectively), were the organisms most susceptible to SH, followed by the Gram-negative bacterium, E. coli (MIC = 0.125 mg/mL) and two yeasts, C. albicans and C. kruei (MIC was 0.125 mg/mL and 0.25 mg/mL, respectively). C. parapsilosis (MIC = 0.75 mg/mL) was the yeast most resistant to SH. The investigation of antimicrobial properties of plant secondary metabolites is important for the development of a new generation of fungicides.

An ATP-fluorescence dual-mode biosensing platform for rapid broad-spectrum enrichment and detection of bacteria based on PEI-functionalized magnetic UiO-66-NH2

Bacteria-induced food pollution poses a serious threat to human health. To detect early and sensitive traces of bacteria in food, a poly (ethyleneimine) (PEI)-modified magnetic organic framework material (Fe3O4@UiO-66-NH2@PEI) was prepared for broad-spectrum enrichment and dual-mode detection of typical gram-positive bacteria (Bacillus subtilis, B. subtilis) and gram-negative bacteria (Escherichia coli, E. coli) using Schiff’s base reaction. Due to the positive charge caused by the abundance of amino groups, Fe3O4@UiO-66-NH2@PEI exhibited rapid enrichment of E. coli and B. subtilis within 12 min through the electrostatic interaction with bacteria. The biosensor based on Fe3O4@UiO-66-NH2@PEI achieved sensitive detection of E. coli and B. subtilis using the adenosine triphosphate (ATP) bioluminescence technology within the detection range of 101-107, and the detection limits were 44 and 57 CFU/mL, respectively under optimal experimental conditions. Moreover, a fluorescence platform was constructed by Fe3O4@UiO-66-NH2@PEI to achieve more diversified detection and reliable detection results for E. coli and B. subtilis. Within the detection range of 101-107, Fe3O4@UiO-66-NH2@PEI exhibited satisfactory linearity with detection limits of 6 CFU/mL and 14 CFU/mL. This biosensor using ATP bioluminescence and fluorescence technology showed remarkable recoveries (85.3–108.5 %) for E. coli and B. subtilis in biscuit matrices, indicating a bright prospect of the dual-mode platform for bacteria detection in food.

Bacteria and Cyanobacteria Inactivation Using UV-C, UV-C/H2O2, and Solar/H2O2 Processes: A Comparative Study

Effective disinfection processes have been investigated to provide pathogen-free drinking water. Due to growing concern about the potential negative effects of cyanobacteria in portable water, their treatment has gained more attention recently. This study aims to compare the inhibition efficiencies of Gram-negative bacteria (Escherichia coli; E. coli), Gram-positive bacteria (Bacillus subtilis; B. subtilis), and cyanobacteria (Microcystis aeruginosa; M. aeruginosa) using UV-C and solar irradiation, and their combination process with H2O2. Over 6 log removal value (LRV) of E. coli and B. subtilis was achieved within 1 min of UV-C irradiation (0.76 ± 0.02 mW/cm2). The solar and solar/H2O2 (50 mg/L) processes effectively reduced (>99%) both bacteria after 20 min. E. coli was more sensitive to hydroxyl radicals (•OH) compared to the B. subtilis due to a different cell wall structure, resulting in a 0.18–0.62 higher LRV than B. subtilis. However, solar-based processes did not effectively inhibit M. aeruginosa (>52.23%). The UV-C/H2O2 (50 mg/L) process showed the highest inhibition rate for M. aeruginosa (77.83%) due to the generation of •OH, leading to oxidative damage to cells. Additionally, chlorophyll-a (Chl-a) was measured to indicate cell lysis of M. aeruginosa. The removal rate of Chl-a extracted by viable M. aeruginosa was higher using the UV-C process (93.03%) rather than the UV-C/H2O2 process (80.95%), because UV-C irradiation could be most effective in damaging Chl-a.

Preliminary Study on Potential Bacterial Species Introducing Antibacterial Agent from Sponge in Unggeh Island Central Tapanuli, Indonesia

Sponges have the potential to symbiont with bacteria that produce antibacterial compounds. This study was conducted to isolate and test the antibacterial activity of sponge symbiont bacteria. Bacterial isolates obtained were tested for antibacterial activity against Staphylococcus aureus, Bacillus subtilis and Escherichia coli using the Kirby-Bauer method. The identification results of both sponges have similarities with Clathria sp. and Hyrtios sp. symbiont bacteria obtained from both sponges as many as 16 isolates. Antibacterial activity testing had a weak inhibitory effect on isolates Sp1A, Sp2C, Sp2D and Sp2F, while Sp2J showed moderate inhibition against gram-negative and positive bacteria. The antibacterial activity of the whole supernatant of symbiont bacteria obtained the diameter of the inhibition zone with weak, medium and strong categories. Sp1A isolate supernatant was obtained, potentially able to fight Escherichia coli bacteria with a strong category as a representation of gram-negative bacteria and against gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) classified into the medium category. In conclusion, 16 symbiont bacterial supernatants have antibacterial activity mostly active against gram-negative bacteria Escherichia coli and gram-positive bacteria Bacillus subtilis. There are 6 isolates (Sp1A, Sp1B, Sp1E, Sp1F, Sp2D, Sp2F) active as antibacterial against Staphylococcus aureus with weak and moderate categories.

Metabolic Profile of the Genome-Reduced Bacillus subtilis Strain IIG-Bs-27-39: An Attractive Chassis for Recombinant Protein Production.

The Gram-positive bacterium Bacillus subtilis is extensively used in the industry for the secretory production of proteins with commercial value. To further improve its performance, this microbe has been the subject of extensive genome engineering efforts, especially the removal of large genomic regions that are dispensable or even counterproductive. Here, we present the genome-reduced B. subtilis strain IIG-Bs-27-39, which was obtained through systematic deletion of mobile genetic elements, as well as genes for extracellular proteases, sporulation, flagella formation, and antibiotic production. Different from previously characterized genome-reduced B. subtilis strains, the IIG-Bs-27-39 strain was still able to grow on minimal media. We used this feature to benchmark strain IIG-Bs-27-39 against its parental strain 168 with respect to heterologous protein production and metabolic parameters during bioreactor cultivation. The IIG-Bs-27-39 strain presented superior secretion of difficult-to-produce staphylococcal antigens, as well as higher specific growth rates and biomass yields. At the metabolic level, changes in byproduct formation and internal amino acid pools were observed, whereas energetic parameters such as the ATP yield, ATP/ADP levels, and adenylate energy charge were comparable between the two strains. Intriguingly, we observed a significant increase in the total cellular NADPH level during all tested conditions and increases in the NAD+ and NADP(H) pools during protein production. This indicates that the IIG-Bs-27-39 strain has more energy available for anabolic processes and protein production, thereby providing a link between strain physiology and production performance. On this basis, we conclude that the genome-reduced strain IIG-Bs-27-39 represents an attractive chassis for future biotechnological applications.

Antibacterial properties of edible coatings from chitosan and young coconut shell liquid smoke

Abstract Liquid smoke-based edible coatings have garnered considerable attention in the food processing and post-harvest industry due to their environmentally friendly attributes and their ability to extend the shelf life of perishable goods. This study investigates the antimicrobial efficacy of edible coatings formulated using chitosan and young coconut shell liquid smoke against both gram-negative bacteria (Escherichia coli and Salmonella typhimurium) and gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus). The liquid smoke was produced via the pyrolysis of young coconut shells at temperatures of 300 (T1), 340 (T2), 380 (T3) and 420ºC (T4). The edible coatings were prepared by blending 2% (v/w) liquid smoke with varying chitosan concentrations of 0.5 % (Ch 0.5), 1% (Ch 1) and 1.5% (Ch 1.5). Antibacterial activity assessments were conducted using the disc diffusion method (Kirby Bauer). The findings reveal that the antibacterial efficacy of the edible coatings against each bacterial strain is influenced by both the pyrolysis temperature and the concentration of chitosan employed. Liquid smoke derived from T4 pyrolysis exhibited the highest inhibitory potential, except for Bacillus subtilis. Notably, the most pronounced antimicrobial activity against Salmonella typhimurium was observed with the T4Ch1.5 edible coating. Specifically, at T4Ch1.5, the inhibitory zones for Escherichia coli, Salmonella typhimurium, Bacillus subtilis, and Staphylococcus aureus were measured at 7.65 mm, 8.30 mm, 7.55 mm, and 7.23 mm, respectively. The results underscore the promise of edible coatings comprising a combination of chitosan and young coconut shell liquid smoke as potential candidates for preserving food and agricultural products, offering both protection and antibacterial properties.

Effect of combined microbial and stress corrosion on 7075 aluminum alloy in high salinity environment

The study investigates the impact of the combination of Gram-positive bacteria Bacillus subtilis (B. subtilis) and tensile stress on the surface corrosion of 7075 aluminum alloy (AA7075) in a high-salt solution environment. The change in PH value caused by the growth curve of bacteria was analyzed for corrosion factors. Scanning electron microscopy (SEM) and ultra-depth 3D microscopy (DOF) were used to compare the surface morphology, elements and corrosion of the samples. The presence of a biofilm reduces the corrosion rate by 0.005 ± 0.0004 mm/y and the application of a constant load results in an increase in the corrosion rate to 0.26 ± 0.013 mm/y. The applied stress leads to the disruption of both the biofilm and oxide film on the metal surface, causing a significant reduction in the impedance isolation effect, and resulting in an expansion of the average diameter and depth of the corrosion pit by 372.21 and 29.5 µm, respectively. In electrochemical impedance testing, there is an approximately 7.01×103 Ω increase in impedance value when exposed to B. subtilis environment; conversely, under stress conditions, there is a decrease by 4.02×103 Ω with B. subtilis present. The corrosion current density has increased fourfold to reach 9.15×10−6 (uA/cm2). This suggests that the combination of bacterial and stress can have a complex and detrimental impact on the corrosion behavior of aluminum alloys in high-salt environments.

Geministatins: new depside antibiotics from the fungus Austroacremonium gemini

Two new depside antibiotics, geministatins A (1) and B (2), were isolated from the fungus Austroacremonium gemini MST-FP2131 (Sordariomycetes, Ascomycota), which was recovered from rotting wood in the wet tropics of northern Australia. The structures of the geministatins were elucidated by detailed spectroscopic analysis, chemical degradation and comparison with literature values. Chemical degradation of 1 and 2 yielded three new analogues, geministatins C–E (3–5), as well as a previously reported compound dehydromerulinic acid A (6). Compounds 1, 2 and 6 exhibited antibacterial activity against the Gram-positive bacteria Bacillus subtilis (MIC 0.2–1.6 µg mL−1) and Staphylococcus aureus (MIC 0.78–6.3 µg mL−1), including methicillin-resistant S. aureus (MRSA), while 4 exhibited antifungal activity against the yeast Saccharomyces cerevisiae (MIC 13 µg mL−1).

Quantification of membrane fluidity in bacteria using TIR-FCS

Plasma membrane fluidity is an important phenotypic feature that regulates the diffusion, function, and folding of transmembrane and membrane-associated proteins. In bacterial cells, variations in membrane fluidity are known to affect respiration, transport, and antibiotic resistance. Membrane fluidity must therefore be tightly regulated to adapt to environmental variations and stresses such as temperature fluctuations or osmotic shocks. Quantitative investigation of bacterial membrane fluidity has been, however, limited due to the lack of available tools, primarily due to the small size and membrane curvature of bacteria that preclude most conventional analysis methods used in eukaryotes. Here, we develop an assay based on total internal reflection-fluorescence correlation spectroscopy (TIR-FCS) to directly measure membrane fluidity in live bacteria via the diffusivity of fluorescent membrane markers. With simulations validated by experiments, we could determine how the small size, high curvature, and geometry of bacteria affect diffusion measurements and correct subsequent measurements for unbiased diffusion coefficient estimation. We used this assay to quantify the fluidity of the cytoplasmic membranes of the Gram-positive bacteria Bacillus subtilis (rod-shaped) and Staphylococcus aureus (coccus) at high (37°C) and low (20°C) temperatures in a steady state and in response to a cold shock, caused by a shift from high to low temperature. The steady-state fluidity was lower at 20°C than at 37°C, yet differed between B. subtilis and S. aureus at 37°C. Upon cold shock, the membrane fluidity decreased further below the steady-state fluidity at 20°C and recovered within 30 min in both bacterial species. Our minimally invasive assay opens up exciting perspectives for the study of a wide range of phenomena affecting the bacterial membrane, from disruption by chemicals or antibiotics to viral infection or change in nutrient availability.

Secretion of the cytoplasmic and high molecular weight β-galactosidase of Paenibacillus wynnii with Bacillus subtilis

BackgroundThe gram-positive bacterium Bacillus subtilis is widely used for industrial enzyme production. Its ability to secrete a wide range of enzymes into the extracellular medium especially facilitates downstream processing since cell disruption is avoided. Although various heterologous enzymes have been successfully secreted with B. subtilis, the secretion of cytoplasmic enzymes with high molecular weight is challenging. Only a few studies report on the secretion of cytoplasmic enzymes with a molecular weight > 100 kDa.ResultsIn this study, the cytoplasmic and 120 kDa β-galactosidase of Paenibacillus wynnii (β-gal-Pw) was expressed and secreted with B. subtilis SCK6. Different strategies were focused on to identify the best secretion conditions. Tailormade codon-optimization of the β-gal-Pw gene led to an increase in extracellular β-gal-Pw production. Consequently, the optimized gene was used to test four signal peptides and two promoters in different combinations. Differences in extracellular β-gal-Pw activity between the recombinant B. subtilis strains were observed with the successful secretion being highly dependent on the specific combination of promoter and signal peptide used. Interestingly, signal peptides of both the general secretory- and the twin-arginine translocation pathway mediated secretion. The highest extracellular activity of 55.2 ± 6 µkat/Lculture was reached when secretion was mediated by the PhoD signal peptide and expression was controlled by the PAprE promoter. Production of extracellular β-gal-Pw was further enhanced 1.4-fold in a bioreactor cultivation to 77.5 ± 10 µkat/Lculture with secretion efficiencies of more than 80%.ConclusionFor the first time, the β-gal-Pw was efficiently secreted with B. subtilis SCK6, demonstrating the potential of this strain for secretory production of cytoplasmic, high molecular weight enzymes.

Influence of seasonality and habitat on chemical composition, cytotoxicity and antimicrobial properties of the Libidibia ferrea

Libidibia ferrea Mart, belonging to the Fabacee family, is a medicinal plant known for its biological properties and production of phenolic compounds. Previous studies reveal the biological activity of its phenolic constituents, making it very promising for the development of new medicines. Seasonality and geographic distribution of species can modify the production of secondary metabolites in Fabaceae species in terms of the preferentially activated metabolic pathways and, consequently, interfere with the medicinal properties of these species. Studying the influence of seasonality on the production of phenolic constituents is essential to establish conditions for “cultivation,” species collection, standardization, production, and safety in traditional medicine. This unprecedented study proposed to evaluate the influence of seasonal variations and habitat on the production of phenolic compounds and biological properties of the ethanolic extracts of the stem bark from L. ferrea, whose specimens were collected from the Caatinga and the Atlantic Forest, biomes of Brazil. Antimicrobial activity was determined by broth microdilution. Cytotoxicity was evaluated through a colorimetric assay using MTT. ABTS and DPPH radical reduction methods estimated antioxidant capacities. Folin-Ciocalteu and AlCl3 spectrophotometric methods quantified total phenolics and flavonoids, respectively. In turn, radial diffusion quantified tannin content. PCA score plot and HCA dendogram were obtained by multivariate analysis of 1H NMR data. The cytotoxicity against C6 glioma cells was observed only for Atlantic Forest extracts (EC50 = 0.13–0.5 mg mL−1). These extracts also showed selectivity against Gram-positive bacteria Bacillus subtilis (ATCC 6633) [MICs 500–2000 μg mL−1], B. cereus CCT 0096) [MIC = 250 μg mL−1], Staphylococcus aureus (ATCC 6538) [MICs = 250–500 μg mL−1], S. epidermidis (ATCC 12228) [62.5–1000 μg mL−1], mainly to Staphylococcus sp. Caatinga extracts showed higher production of flavonoids and antioxidants in the summer [7.36 ± 0.19 μg QE mg−1 extract; IC50ABTS = 4.86 ± 0.05 μg mL−1], spring [5.96 ± 0.10 μg QE mg−1 extract; IC50ABTS = 5.96 ± 0.08 μg mL−1 ], winter [4.89 ± 0.25 μg QE mg−1 extract; IC50ABTS = 6.72 ± 0.08 μg mL−1 ]. Regarding habitat, two discriminating compound patterns in the studied biomes were revealed by NMR. The results indicated that the Caatinga biome offers better conditions for activating the production of phenolics [336.34 ± 18.1 μgGAE mg−1 extract], tannins [328.38 ± 30.19 μgTAE mg−1 extract] in the summer and flavonoids in winter, spring, and summer. The extracts that showed the best antioxidant activities were also those from the Caatinga. In turn, extracts from the Atlantic Forest are more promising for discovering antibacterial compounds against Staphylococcus sp and cytotoxic for C6 glioma cells. These findings corroborated the traditional use of L. ferrea bark powder for treating skin wounds and suggest the cytotoxic potential of these extracts for glioblastoma cell lines.

Combined effect of brazilin-rich extract and lawsone methyl ether against infection-causing bacteria

Bacterial contamination and infection widely affect the food, pharmaceutical and biomedical industries. Additionally, these bacteria developed resistance to synthetic antibiotics causing public health danger, globally. Natural plant extracts (NPE) are suitable alternatives to synthetic antibiotics to tackle antimicrobial resistance problems. Furthermore, a blend or combination of different NPEs exerts a wide spectrum of antimicrobial activity. Therefore, the combined effect of brazilin-rich extract (BRE) and lawsome methyl ether (LME) against infection-causing common bacteria were evaluated. BRE had a lower minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against most of the Gram-negative bacteria (Salmonella typhi, Salmonella typhimurium and Pseudomonas aeruginosa) while LME was active against most of the Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus, and Staphylococcus epidermidis). The combination of BRE and LME at 2:1 and 1:1 concentration significantly reduced the MIC value of each compound as compared to either BRE or LME concentration alone (P < 0.05). Further time-kill kinetics revealed a 3.0–3.5 log reduction in Gram-positive bacteria and a 2.5–3.0 log reduction in Gram-negative bacteria during 120 min of incubation, respectively. Therefore, a combination of BRE and LME was recommended as natural antibacterial to synthetic antibiotics for food and pharmaceutical applications.

Phytoconstituents of a traditional herb, Verbascum sinaiticum Benth mediated zinc-ferric bimetallic nanoparticle synthesis and bioactive properties for sustainable application

Verbascum sinaiticum Benth, a traditional medicinal plant renowned for its therapeutic properties, was investigated for its phytochemical composition and bioactivity. Aqueous, hexane, and ethanol extracts were qualitatively and quantitatively analyzed for phytochemicals. The hexane extract exhibited tannins, phenolics, and coumarin, while the ethanol extract displayed phenolics, quinones, coumarin, and saponins. Bimetallic nanoarticles were synthesized by ultrasonication method assisted by the plant extracts and characterized by FTIR spectroscopy,X-Ray diffraction methods and SEM analysis.Characterization studies revealed nanoparticle sizes ranging between 63.54 nm and 91.36 nm, while Gas Chromatography-Mass Spectrometry identified bioactive compounds including 9,12,15-octadecatrienoic acid and hexadecenoic acid. The ethanol and aqueous extracts of V. sinaiticum exhibited a significant range of antibacterial activity against tested gram-positive bacterium (Bacillus subtilis) and both gram-negative bacteria and against Streptococcus mutans and both the gram-negative bacteria respectively. The hexane extract of V. sinaiticum exhibited less activity against Bacillus subtilis (5–11 mm) and Escherichia coli (8–12 mm) and has exhibited significant antibacterial activity against Streptococcus mutans (16–23 mm) and Pseudomonas aeruginosa (15–22 mm). The hexane extract of exhibited a significant range of antifungal activity against Candida albicans and Aspergillus niger, with an average zone of inhibition ranging from 7 mm to 18 mm in diameter.The ethanol extract showed a narrow range of antifungal activity against Aspergillus niger. The aqueous extract exhibited potent antioxidant activity with an EC50 value of 42.3 µg/mL. This comprehensive methodology sheds light on the medicinal potential of Verbascum sinaiticum Benth extract mediated bimetallic nanoparticles and provides insights for further research and applications.

Multifunctional Ag2O/chitosan nanocomposites synthesized via sol-gel with enhanced antimicrobial, and antioxidant properties: A novel food packaging material

In this study, a single step in situ sol-gel method was used to syntheses nanocomposite films using chitosan (CS) as the basis material, with the addition of silver oxide nanoparticles (Ag2O) at several weight percentages (5 %, 10 %, and 15 % Ag2O/CS). The structural characteristics of Ag2O/CS films were investigated using a range of analytical techniques. The presence of the primary distinctive peaks of chitosan was verified using FTIR spectra analysis. However, a minor displacement was observed in these peaks due to the chemical interaction occurring with silver oxide molecules. XRD analysis demonstrated a significant increase in the crystallinity of chitosan when it interacted with metal oxide nanoparticles. Furthermore, it is believed that the interaction between silver oxide and the active binding sites of chitosan is responsible for the evenly dispersed clusters shown in the micrographs of the chitosan surface, as well as the random aggregations within the pores. EDS technique successfully identified the presence of distinctive silver signals within the nanocomposite material, indicating the successful absorption of silver into the surface of the polymer. The developed Ag2O/CS nanocomposite showed promising antibacterial activity against Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Bacillus subtilis, Enterococcus faecalis and Staphylococcus aureus). Also, Ag2O/CS nanocomposite exhibited marked antifungal activity against Candida albicans, Aspergillus flavus, A. fumigatus, A. niger, and Penicillium chrysogenum. The antioxidant activity of the developed nanocomposite films was studied by ABTS radical scavenging. The highest antioxidant and antibacterial properties were achieved by including 15 % silver oxide into the chitosan. Therefore, our finding indicate that chitosan‑silver oxide nanocomposites exhibits significant potential as a viable material for application in several sectors of the food packaging industry.

The high impact of zinc chromium oxide nanocombs on development of larvicidal and antimicrobial performance

Zinc chromium oxide (Cr/ZnO, 5wt.%) was prepared by a facile chemical co-precipitation route. The structure, composition, and chemical bonding were analyzed using X-ray diffraction (XRD), Energy dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy (FTIR) indicating that chromium ions were integrated the host framework to form Cr/ZnO nanocomposite. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) micrographs showed comb-shaped nanoparticles with an average size 20 nm and large surface area. The energy gap of the thin films was estimated from T% and R% measurements which exhibit a strong optical absorption edge close to the visible spectrum. The insecticidal activity of the synthesized nanocombs against C. pipiens larvae was evaluated with LC50 (30.15 ppm) and LC90 (100.22 ppm). Besides, the nanocomposite showed high antibacterial performance against gram-positive bacteria (Bacillus subtilis) and gram-negative bacteria (Proteus vulgaris) with inhibition zones 21.9 and 19 mm, respectively.

Perception of butenolides by Bacillus subtilis via the α/β hydrolase RsbQ

The regulation of behavioral and developmental decisions by small molecules is common to all domains of life. In plants, strigolactones and karrikins are butenolide growth regulators that influence several aspects of plant growth and development, as well as interactions with symbiotic fungi.1,2,3 DWARF14 (D14) and KARRIKIN INSENSITIVE2 (KAI2) are homologous enzyme-receptors that perceive strigolactones and karrikins, respectively, and that require hydrolase activity to effect signal transduction.4,5,6,7 RsbQ, a homolog of D14 and KAI2 from the gram-positive bacterium Bacillus subtilis, regulates growth responses to nutritional stress via the alternative transcription factor SigmaB (σB).8,9 However, the molecular function of RsbQ is unknown. Here, we show that RsbQ perceives butenolide compounds that are bioactive in plants. RsbQ is thermally destabilized by the synthetic strigolactone GR24 and its desmethyl butenolide equivalent dGR24. We show that, like D14 and KAI2, RsbQ is a functional butenolide hydrolase that undergoes covalent modification of the catalytic histidine residue. Exogenous application of both GR24 and dGR24 inhibited the endogenous signaling function of RsbQ invivo, with dGR24 being 10-fold more potent. Application of dGR24 to B.subtilis phenocopied loss-of-function rsbQ mutations and led to a significant downregulation of σB-regulated transcripts. We also discovered that exogenous butenolides promoted the transition from planktonic to biofilm growth. Our results suggest that butenolides may serve as inter-kingdom signaling compounds between plants and bacteria to help shape rhizosphere communities.

Antibacterial activity of five Indonesian medicinal plants and the isolation of compounds from Plectranthus scutellarioides

The purpose of this study is to investigate the antibacterial properties of five Indonesian medicinal plant extracts, namely Physalis angulata, Loranthus parasiticus, Plectranthus scutellarioides, Cyperus rotundus, and Terminalia catappa. The isolation of compounds from P. scutellarioides against pathogenic bacteria was also investigated. The assessment of the antibacterial activity of the extracts was conducted using the microdilution-3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide method against Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli). The plant extract with the highest antibacterial activity was further purified using various chromatographic assays to isolate bioactive compounds. High Resolution-Electron Ionization Mass Spectroscopy/Electrospray Ionization Mass Spectroscopy (HR-ESIMS/EIMS) and Nuclear Magnetic Resonance (NMR) spectrometers were used to elucidate the structure of isolated compounds. Among all the plants tested, P. scutellarioides showed the strongest antibacterial activity against S. aureus [minimum inhibitory concentration (MIC 100 μg/ml)] and B. subtilis (MIC 200 μg/ml). Three compounds were isolated from P. scutellarioides including an abietane diterpene, 2,16-diacetoxy-6,11,12,14,17-pentahydroxy-abieta-5,8,11,13- tetraene-7-one (1), 5,6,7,3′,4′,5′-hexamethoxy flavone (2), and 5,6,7,8,3′,4′,5′-heptamethoxy flavone (3). Compounds 2 and 3 were recognized to be first isolated from this plant. Compound 1 exerted antibacterial activity against S. aureus with a MIC value of 60 μM, but was inactive against B. subtilis and E. coli (MIC &gt; 200 μM). Compounds 2 and 3 were inactive against S. aureus, B. subtilis, and E. coli (MIC &gt; 200 μM).

Synthesis of copper nanoparticles by a sonication-mediated method using Malpighia glabra fruit extract and their applications.

This study introduces an environmentally friendly technique for copper nanoparticle synthesis utilizing Malpighia glabra fruit extract under the sonication treatment. The synthesis process and phenol red removal were optimized by a central composite full and response surface design. Highly pure and spherical-shaped copper nanoparticles with an average size of 22.5 nm were formed using 7.4 mL of Malpighia glabra fruit extract and 21.9 mM (AcO)2Cu. Additionally, the extract-mediated nanoparticles opposed the negative charges with a zeta potential of -11.8 mV and high stability of 30 days storage time. The sonication-assisted nanoparticles exhibited the highest inhibition against Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), MCF7 human breast cancer cells, and Fusarium solani with 50% inhibition concentrations reaching 12, 0.82, and 80 ppm, respectively. Additionally, the green-synthesized nanomaterials functioned as an effective catalyst to remove phenol red. A conversion of 97% after a 540 seconds reaction was determined on 10 ppm phenol red with the presence of 21.5 ppm copper nanoparticles and 51.8 mM NaBH4. This research highlights the potential of Malpighia glabra fruit extract in the sustainable production of copper nanoparticles, with promising applications in biomedicine, agriculture, and environmental remediation.

Enhancing biofouling resistance in microfiltration membranes through capsaicin-derivative functionalization.

The primary focal point in the fabrication of microfiltration membranes revolves around mitigating issues of low permeability stemming from the initial design as well as countering biofouling tendencies. This work aimed to address these issues by synthesizing an antibacterial capsaicin derivative (CD), which was then grafted to the poly(vinylidene fluoride-co-chlorotrifluoroethylene)-g-polymethacrylic acid (P(VDF-CTFE)-g-PMAA) matrix polymer, resulting in an antibacterial polymer (PD). Notably, both CD and PD demonstrated low cytotoxicities. Utilizing PD, a microfiltration membrane (MA) was successfully prepared through non-solvent-induced phase inversion. The pore sizes of the MA membrane were mainly concentrated at around 436 nm, while the pure water flux of MA reached an impressive value of 62 ± 0.17 Lm-2 h-1 at 0.01 MPa. MA exhibited remarkable efficacy in eradicating both Gram-negative (E. coli) and Gram-positive bacteria (Bacillus subtilis) from its surface. Compared with M1 prepared from P(VDF-CTFE), MA exhibited a lower flux decay rate (41.00% vs. 76.03%) and a higher flux recovery rate (84.95% vs. 46.54%) after three cycles. Overall, this research represents a significant step towards the development of a microfiltration membrane with inherent stable anti-biofouling capability to enhance filtration.