Antimicrobial Ability Research Articles

Polydopamine/tannic acid/chitosan/poloxamer 407/188 thermosensitive hydrogel for antibacterial and wound healing

The design and development of smart shape-adaptable wound dressings with superior antimicrobial ability remain a challenge in therapeutic and clinical application. Herein, polydopamine/tannic acid/chitosan/poloxamer 407/188 hydrogel (PTCPP) was prepared with the aim of developing an in situ-formed antibacterial wound dressing with temperature stimulation and near-infrared radiation (NIR) responsive ability. PTCPP possessed injectability, photothermal stability, sustained release properties and cytocompatibility. In vitro antibacterial results showed that the bactericidal rates of PTCPP against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) under NIR irradiation were 99.994 % and 99.91 %, respectively. In vivo experiments, PTCPP can adapt to shape of the wound, showing good adhesion, while promoting wound healing in bacterial infections. Therefore, PTCPP has potential application in the treatment of infectious wounds, and provides a strategic choice for developing antibacterial wound dressing combined with photothermal therapy.

Polyetheretherketone/Nano‐Ag‐TiO2 composite with mechanical properties and antibacterial activity

AbstractPolyetheretherketone (PEEK) is of interest because of its excellent biocompatibility. However, the lack of antimicrobial activity of PEEK limits its use in clinical applications. Silver‐loaded nano titanium dioxide (Nano‐Ag‐TiO2)/PEEK composites with different mass fractions (1, 2, 3, and 4 wt%) were prepared by hot compression molding to achieve better mechanical and antimicrobial properties. The results of scanning electron microscopy (SEM) and energy dispersive spectrum (EDS) showed that Nano‐Ag‐TiO2 successfully modified PEEK. The contact angle of Nano‐Ag‐TiO2/PEEK increased compared to PEEK (p < 0.01). The flexural strength, compressive strength, and Vickers hardness of Nano‐Ag‐TiO2/PEEK composites first increased and then decreased. When the Nano‐Ag‐TiO2 content is 3 wt%, the flexural strength of Nano‐Ag‐TiO2/PEEK composite reaches its maximum, which is 171.19 MPa; the compressive strength reaches the maximum, which is 24.7% higher than that of pure PEEK specimens; the Vickers hardness of Nano‐Ag‐TiO2/PEEK composite reaches its maximum, which is 19.84% higher than that of pure PEEK specimens. The in vitro antibacterial evaluation reveals that all Nano‐Ag‐TiO2/PEEK samples exhibited good resistance and anti‐adhesive properties against Staphylococcus aureus (S. aureus). This finding suggests that the 3 wt% Nano‐Ag‐TiO2/PEEK composite has better mechanical properties and antimicrobial ability, which is promising for dental applications.

Screening and identification of lactic acid bacteria with antimicrobial abilities for aquaculture pathogens in vitro

This study aimed to evaluate the antibacterial properties of nine lactic acid bacterial strains. The agar diffusion method (Oxford cup method) was used to assess the antimicrobial activity against pathogenic bacteria in aquaculture. The results showed that all selected strains inhibited the growth of Photobacterium damsel, Vibrio alginolyticus, Listonella anguillarum, Edwardsiella ictaluri, Aeromonas hydrophila, V. arahaemolyticus, Edwardsiella tarda and V. harveyi, but did not inhibit the growth of Metschnikowia bicuspidata. Among these strains of lactic acid bacteria, r1 was selected for its obvious antibacterial activity against eight kinds of pathogenic bacteria by 96-well plate method. Its inhibitory rate reached 96%, and it could inhibit the growth of six pathogenic bacteria at 121℃, 20min and pH 3.5-4.0. It was identified as Lactiplantibacillus plantarum by morphological observation and 16S rRNA sequencing analysis. Because strain r1 was isolated from culture ponds and exerted strong inhibitory effects on pathogenic bacteria, it holds potential as an agent to prevent and control infectious diseases in aquaculture. This study provides a foundation for the development and utilization of probiotics in aquaculture.

A coupled molybdenum disulfide - copper modification of NF membrane for enhanced anti-bacterial performance

Biofouling is a bottleneck in restricting nanofiltration (NF) application for drinking water treatment. In current study, we reported a novel molybdenum disulfide (MoS2) ‑ copper (Cu2+) modification of polyamide NF membrane for enhanced anti-bacterial performance. The incorporation of Cu2+ into the separation layer through interfacial polymerization was to enhance the anti-microbial ability, while the introduction of lamellar MoS2 into the polyamide active layer was to stably immobilize copper, as well as to provide an interlayer nanochannels for water transport and also to enhance membrane hydrophilicity. The resultant membrane showed an excellent anti-bacterial ability, with 99.1% and 96.7% inactivation efficiencies of Escherichia coli and Bacillus subtilis, respectively, at MoS2 - Cu molar ratio of 1:0.3. Compared to the control membrane, the obtained membrane exhibited a 44% increase of pure water flux. Membrane stability assessment indicated that > 93% of initial loaded Cu2+ and Mo4+ remained in the membrane matrix after a 5-d shaking test. Membrane characterization suggested that the MoS2 - Cu complexes were uniformly dispersed into the membrane active layer, which led to an increased membrane roughness that was favorable for antibiofouling. Overall, the facile MoS2 – Cu addition with intensified anti-biofouling ability created in this study provides a promising membrane modification approach for practical application.

Preparation and characterization of carvacrol essential oil-loaded halloysite nanotubes and their application in antibacterial packaging

Carvacrol (CA), a volatile plant essential oil, can pervade the headspace of containers and has high antimicrobial efficiency when it is applied in the food packaging system. Here, CA was encapsulated into halloysite nanotubes (HNTs) to form the carvacrol-loaded halloysite nanotubes (CA-HNTs) compounds. The results show that CA was successfully encapsulated in HNTs with the highest loading efficiency of 17%. The CA-HNTs compounds possessed a significant improvement in their thermal stability and acquired a sustained release ability supported by that 33.8% of CA was released at 40 ℃ after a long 25 days of storage. On this basis, the fabricated zein films containing 8 wt% CA-HNTs presented the maximum inhibition efficiency against Escherichia coli and Staphylococcus aureus. Benefiting from the antimicrobial ability and slow-release effects, the CA-HNTs-loaded films greatly prolonged the shelf-life of cherry tomatoes. Therefore, CA-HNTs are novel and valid antimicrobial component for food packaging.

Antibacterial Effect of Triazine in Barrier Membranes with Therapeutic Activity for Guided Bone Regeneration.

This study aimed to develop polymer-based barrier membranes based on poly(butylene-adipate-co-terephthalate) (PBAT) with the addition of 1,3,5-triacriloilhexahydro-1,3,5-triazine (TAT). Polymeric solutions were used to produce membranes with 5 wt% and 10 wt% of TAT by solvent casting. Membranes without the addition of TAT were used as controls. The membranes were chemically characterized by Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TGA); surface properties were assessed by profilometry and contact angle; the mechanical behavior was evaluated by a tensile test, and the biological properties were assessed by direct-indirect cell viability and antibacterial activity by S. mutans and S. aureus colony-forming units. TAT was detected in the FTIR and TGA analyses and modified the top surface of the membranes, increasing their roughness and wetness in both concentrations compared to the control group (p < 0.05). The addition of TAT, regardless of concentration, reduced the tensile strength and increased membrane stiffness (p < 0.05). The cell viability of 5 wt% TAT and 10 wt% TAT was 86.37% and 82.36%, respectively. All tested concentrations reduced the formation of biofilm on the membranes when compared to the control. The addition of TAT successfully resulted in the antimicrobial ability of PBAT-based barrier membranes, while it maintained acceptable levels of cell viability in membranes with adequate handling and surface properties.

Biosynthesis Investigations of Terpenoid, Alkaloid, and Flavonoid Antimicrobial Agents Derived from Medicinal Plants.

The overuse of antibiotics in the past decades has led to the emergence of a large number of drug-resistant microorganisms. In recent years, the infection rate caused by multidrug-resistant microorganisms has been increasing, which has become one of the most challenging problems in modern medicine. Plant-derived secondary metabolites and their derivatives have been identified to display significant antimicrobial abilities with good tolerance and less adverse side effects, potentially having different action mechanisms with antibiotics of microbial origin. Thus, these phyto-antimicrobials have a good prospect in the treatment of multidrug-resistant microorganisms. Terpenoids, alkaloids, and flavonoids made up the predominant part of the currently reported phytochemicals with antimicrobial activities. Synthetic biology research around these compounds is one of the hotspot fields in recent years, which not only has illuminated the biosynthesis pathways of these phyto-antimicrobials but has also offered new methods for their production. In this review, we discuss the biosynthesis investigations of terpenoid, alkaloid, and flavonoid antimicrobial agents—using artemisinin and oleanolic acid (terpenoids), berberine and colchicine (alkaloids), and baicalin (flavonoids) as examples—around their antimicrobial action mechanisms, biosynthesis pathway elucidation, key enzyme identification, and heterologous production, in order to provide useful hints for plant-derived antimicrobial agent discovery and development.

Carbon Dots for Killing Microorganisms: An Update since 2019.

Frequent bacterial/fungal infections and occurrence of antibiotic resistance pose increasing threats to the public and thus require the development of new antibacterial/antifungal agents and strategies. Carbon dots (CDs) have been well demonstrated to be promising and potent antimicrobial nanomaterials and serve as potential alternatives to conventional antibiotics. In recent years, great efforts have been made by many researchers to develop new carbon dot-based antimicrobial agents to combat microbial infections. Here, as an update to our previous relevant review (C 2019, 5, 33), we summarize the recent achievements in the utilization of CDs for microbial inactivation. We review four kinds of antimicrobial CDs including nitrogen-doped CDs, metal-containing CDs, antibiotic-conjugated CDs, and photoresponsive CDs in terms of their starting materials, synthetic route, surface functionalization, antimicrobial ability, and the related antimicrobial mechanism if available. In addition, we summarize the emerging applications of CD-related antimicrobial materials in medical and industry fields. Finally, we discuss the existing challenges of antimicrobial CDs and the future research directions that are worth exploring. We believe that this review provides a comprehensive overview of the recent advances in antimicrobial CDs and may inspire the development of new CDs with desirable antimicrobial activities.

Bryophyllum pinnatum mediated synthesis of zinc oxide nanoparticles: characterization and application as biocontrol agents for multi-drug-resistant uropathogens

The emerging era of antimicrobial resistance has become a challenge for the potentiality of current antibiotic therapy, making the treatment of several diseases, including urinary tract infections (UTIs) very chaotic. To combat the present circumstances, there is an urge among the scientific community to find efficient substitutes for antibiotic therapy, which may potentially delimit the antimicrobial resistance among the various uropathogens. In this direction, the upcoming field of nanotechnology holds a high potential. Therefore, the present study aimed at the evaluation of the antimicrobial potential of green synthesized zinc oxide nanoparticles. The nanoparticles were synthesized using Bryophyllum pinnatum plant leaf extract and were characterized with the help of several analytical techniques. A sharp peak obtained at 369 nm by UV-Visible spectroscopy affirmed the synthesis of Bryophyllum- ZnO nanoparticles, and the FTIR spectroscopy confirmed the conjugation of different phytochemicals. XRD analysis revealed the crystallinity and hexagonal conformation, and through SEM and HR-TEM, the particle size of the synthesized Bryophyllum- ZnO nanoparticles was found to be between 14-35 nm. The synthesized green nanoparticles, when tested against a few highly MDR uropathogenic bacteria (E. coli, E. furgusonii, K. pneumoniae, S. flexneri, and P. aeruginosa), were observed to exhibit high antimicrobial response (zones of inhibition ranging between 22 mm to 28 mm), thus confirming that these were bestowed with potent antimicrobial ability. Hence, from the present work, it could be concluded that Bryophyllum- ZnO nanoparticles can be used as potential nanoantibiotic sources to deal with UTIs.

Synthesis and evaluation of the antioxidant activity of new spiro-1,2,4-triazine derivatives applying Ag/Fe3O4/CdO@MWCNT MNCs as efficient organometallic nanocatalysts.

We applied the Petasites hybridus rhizome water extract as green media so that Ag/Fe3O4/CdO@ multi-walled carbon nanotubes magnetic nanocomposites (Ag/Fe3O4/CdO@MWCNTs MNCs) could be prepared. We also evaluated its activity by using in the one-pot multicomponent reaction of acetophenones, diethyl oxalate, ammonium acetate, and activated carbonyl compounds such as ninhydrin, isatin and acenaphthylene-1,2-dione, and malononitrile and hydrazoyl chlorides in an aqueous medium at room temperature for the generation of spiro-1,2,4-triazines as new derivatives with tremendous output. Moreover, reducing organic pollutants from 4-nitrophenol (4-NP) was carried out by generating Ag/Fe3O4/CdO@MWCNTs in water at room temperature. The results displayed that Ag/Fe3O4/CdO@MWCNTs reduced pollutants of organic compounds in a short time. The synthesized spiro-1,2,4-triazines have NH and OH functional groups having acidic hydrogen with high antioxidant power. Also, the spiro-1,2,4-triazines exhibited antimicrobial ability. For this purpose, the disk diffusion method was applied and two kinds of bacteria, Gram-positive and Gram-negative, were employed for the analysis. Furthermore, we applied functional theory-based quantum chemical methods in order to better understand reaction mechanism density. To generate spiro-1,2,4-triazines, the applied process showed many properties such as reactions with short time, products with good yields, and simple extraction of catalyst from a mixture of reactions.

Six-component synthesis and biological activity of novel spiropyridoindolepyrrolidine derivatives: A combined experimental and theoretical investigation.

Petasites hybridus rhizome water extract was used as green media for the preparation of Ag/Fe3O4/CdO@multi-walled carbon nanotubes magnetic nanocomposites (Ag/Fe3O4/CdO@MWCNTs MNCs), and its activity was evaluated by using in the one-pot multicomponent reaction of isatins, acetyl chloride, secondary amines, vinilidene Meldrum’s acid, primary amines, and malononitrile in an aqueous medium at room temperature for the generation of spiropyridoindolepyrrolidine as new derivatives with tremendous output. In addition, organic pollutant reduction of 4-nitrophenol (4-NP) was carried out by generated Ag/Fe3O4/CdO@MWCNTs in water at room temperature. The results displayed that Ag/Fe3O4/CdO@MWCNTs were reduced as pollutants of organic compounds in a short time. The synthesized spiropyridoindolepyrrolidine has an NH2 functional group that has acidic hydrogen and shows high antioxidant ability. Also, the spiropyridoindolepyrrolidine exhibited antimicrobial ability, and the method that is used for this purpose is the disk diffusion method, and two kinds of bacteria, Gram-positive and Gram-negative, were employed for this analysis. Also, to better understand the reaction mechanism density, functional theory-based quantum chemical methods have been applied. For the generation of spiropyridoindolepyrrolidine, the used process has many properties such as reactions with short time, product with good yields, and simple extraction of catalyst from the mixture of reaction.

An accurate strategy for pointing the key biocatalytic sites of bre2691A protein for modification of the brevilaterin from Brevibacillus laterosporus

BackgroundBrevilaterin A-E, a novel class of multi-component cationic antimicrobial lipopeptides, were biosynthesized by a non-ribosomal peptides synthetase (NRPS) in Brevibacillus laterosporus. However, the antimicrobial abilities of different brevilaterin components varied greatly, and this multi-component form was impeding the scale production of the excellent component, and a little information about the brevilaterin biosynthesis mechanism was available to apply in brevilaterin design modification. In this study, we used an accurate strategy that revealed the reason for producing multi-component was the substrate selectivity of bre2691A protein being not enough specific and pinpointed the key design sites to make the specificity of bre2691A enhanced.ResultsBioinformatic analysis revealed that the biocatalytic site of bre2691A, which was an adenylation domain catalyzed and recognized methionine, leucine, valine and isoleucine and thus introduced them into brevilaterins and caused different components (brevilaterin A-E), was consisted of A1 ~ A10 residues named specificity-conferring code. Coupling molecular docking simulations with mutation studies identified A2 and A7 as critical residues, where determined substrate-specificity and impacted activity. The in virto activity assay showed that the A2 mutant (G193A) would lose activity against methionine and have no effect on the other three amino acids, the A7 mutant (G285C) would enhance the catalytic activity against four substrates, especially against leucine at almost a double activity. When the A2 and A7 residues were synchronously mutated, this mutant would be more focused on recognizing leucine.ConclusionsAn accurate strategy that combined with bioinformatics and site-directed mutation techniques revealed the pivotal site A2 and A7 positions of bre2691A protein that could be used to design and modify brevilaterins, thus further providing a reasonable direction of genetic engineering for Brevibacillus laterosporus. A deeper understanding of the function of crucial residues in the adenylation domain would make it get more accurate and highly efficient design and more fully utilized. Furthermore, it would contribute to biotechnological applications, namely for the large centralized synthesis of antimicrobial peptides, or for the optimization of their production.Graphic

Green Synthesis and Study of Biological Activity of New Benzopyrimidoazepines: Reduction of Organic Pollutants Using Synthesized Fe3O4/TiO2/CuO@MWCNTs MNCs

In this work rhizome of Petasites hybridus was used for preparing water extract and utilized as green media for generating Fe3O4/TiO2/CuO@ Multi-Walled Carbon Nanotubes (MWCNTs) magnetic nanocomposites and its activity was evaluated by using in the one-pot multicomponent reactions (MCRs) of anilines, diethyl oxalate, activated acetylenic compounds, α-haloketones, ammonium acetate and aroyle(alkaloyl)isocyanates in aqueous at room temperature to produce of novel benzopyrimidoazepine derivatives in excellent yields. Moreover, the reduction of organic pollutants such 4-nitrophenol (4-NP) was performed by synthesized Fe3O4/TiO2/CuO@MWCNTs in H2O at room temperature. The outcomes showed this catalyst was decreased organic contaminants in the low time. The generated benzopyrimidoazepines have hydroxyl and two NH functional groups that have acidic hydrogen and show high antioxidant activity. The antioxidant activity order of some synthesized compounds was as TBHQ ≈ BHT>7b>7d>7c>7a. Also, antimicrobial ability of obtained benzopyrimidoazepines was investigated with the disk diffusion method, and two Gram-negative and Gram-positive bacteria and compounds 7b, 7c, 7e, and 7g have maximum effect on Escherichia coli relative to Gram positive and negative bacteria due to good diameter of inhibition zone. The short time of reactions, excellent efficiency of product, easy separation of catalyst and products employed process to the synthesis of benzopyrimidoazepines are some advantages of this procedure. HIGHLIGHTS Green chemistry is the use of a set of principles to reduce or eliminate the use or generation of unsafe materials in the design, fabrication, and applications of chemical products. Among solvents, water is a green solvent and very suitable for performing the organic reaction. The present procedure avoids the use of toxic solvents. Heterocyclic compounds hold a prominent position in medicinal chemistry owing to their wide spectrum of biological activities, such as antimalarial, antimicrobial, antitumor, anticancer, antidepressant, antiviral, antidiabetic, anti-inflammatory, and anti-HIV. The benzoazepine skeleton is a famous pharmacophore that is existed in several behavioral disorder drugs, such as imipramine, diazepam, and lorazepam.

Antibiotic resistance pattern of Extended-Spectrum ?-Lactamase (ESBL) producing Escherichia coli isolated from broiler farm environment in Pasuruan district, Indonesia

Abstract. Yanestria SM, Dameanti FNAEP, Musayannah BG, Pratama JWA, Witaningrum AM, Effendi MH, Ugbo EN. 2022. Antibiotic resistance pattern of Extended-Spectrum ?-Lactamase (ESBL) producing Escherichia coli isolated from broiler farm environment in Pasuruan district, Indonesia. Biodiversitas 23: 4460-4465. Escherichia coli is one of the bacteria that can be used as an indicator of environmental pollution. This bacterium has the ability to become an antimicrobial-resistant bacterium that impacts public health. The antimicrobial ability can develop into a bacterium that produces extended-spectrum ?-lactamase (ESBL). The purpose of this study was to reveal the occurrence of extended-spectrum ?-lactamase (ESBL) producing E. coli from a broiler farm environment in Pasuruan district and to describe the phenotypic pattern of E. coli producing ESBL that has been detected. A total of 175 samples were used in this study consisting of 115 samples of coop swabs and 65 samples of wastewater around the farm. The samples were isolated and identified to find E. coli by using different culture media viz. McConkey agar (MCA), eosin methylene blue agar (EMBA), Gram staining, indole test, methyl red Voges Proskauer (MR-VP), citrate, and triple sugar iron agar (TSIA). Detection of ESBL using the double disc synergy test (DDST) according to standard Clinical and Laboratory Standards Institute procedures and the VITEK®2 compact apparatus. The results of ESBL confirmation with DDST and VITEK®2 showed that 16 (9.14%) of the 175 environmental samples confirmed E. coli produced ESBL. The results of the VITEK®2 test also produced a phenotypic pattern of resistance properties of ESBL-producing E. coli and found 12 types of resistance patterns. The combination of “AM AMP ATM KZ CTX CRO CIP” and “AM AMP ATM KZ CTX CRO GM CIP SXT” are the 2 most common resistance patterns (18.75%), while the other 10 resistance patterns occur at the same level (6.25%). The data presented here confirmed the presence of ESBL-producing E. coli in the farm environment, which can contribute to the dissemination of MDR bacteria in the environment if not monitored. Therefore, the presence of ESBL-producing E. coli in Pasuruan is worrisome since it can lead to an impact on human health.

Bacterial Metabolite Reuterin Attenuated LPS-Induced Oxidative Stress and Inflammation Response in HD11 Macrophages.

Reuterin is well-known for its broad-spectrum antimicrobial ability, while the other potential bioactivity is not yet clear. The present study aims to investigate the immunomodulatory activity of reuterin on chicken macrophage HD11 cells for the first time and evaluate whether reuterin is able to regulate the lipopolysaccharide-stimulated inflammatory response. The results showed that the safe medication range of reuterin was less than 250 μM. Reuterin treatment for 6 h decreased the transcriptional of CD86, IL-1β and iNOS and increased the expression of CD206 in a dose-dependent way, but reuterin treatment for 12 h contrary increased the expression of IL-1β, IL-6 and IL-10. However, it was noticed that reuterin treatment for 12 h significantly decreased the production of reactive oxygen species (ROS) and suppressed the phagocytosis activity of HD11 macrophages against bacteria. Further, the results showed that preincubation or coincubation with reuterin significantly attenuated the promotive effects of lipopolysaccharide (LPS) on transcription of proinflammatory cytokines (including IL-1β, IL-6 and TNF-α) and obviously inhibited nitric oxide (NO) production as well as the protein expression of inducible nitric oxide synthase (iNOS). Meanwhile, Mechanism studies implied that reuterin might exert an anti-inflammatory effect on LPS-stimulated cells by downregulating the expression of TLR4/MyD88/TRAF6 and blocking the activation of NF-κB as well as MAPKs signaling pathways. Additionally, it was found that both pretreatment and cotreatment with reuterin remarkably inhibited the oxidative stress induced by LPS stimulation by activating the Nrf2/HO-1 signaling pathway and enhancing the activities of antioxidative enzymes. These findings suggested the immunoregulatory function of reuterin and indicated this bacterial metabolite was able to inhibit the inflammation and oxidative stress of HD11 macrophages once exposed to LPS stimulation.

Controlled drug delivery and cell adhesion for bone tissue regeneration by Keplerate polyoxometalate (Mo132)/metronidazole/PMMA scaffolds

The aim of this study is to fabricate a new scaffold appropriate for tissue regeneration with antimicrobial activity and ability of controlled drug delivery. In this regard, scaffold nanofibers were produced using poly (methyl methacrylate) (PMMA), Mo132 as a Keplerate polyoxometalate and metronidazole. The final scaffolds, obtained by electrospinning, represent the intrinsic features including exceptional doubling tensile strength, high hydrophilicity (126 ± 5.2° to 83.9 ± 3.2° for contact angle and 14.18 ± 0.62% to 35.62 ± 0.24% for water uptake), proper bioactivity and cell adhesion. Moreover, the addition of Mo132 and metronidazole enhances the biodegradation rate of resulted scaffolds compared to the pure PMMA membrane. The controlled release of metronidazole over 14 days efficiently inhibits the colonization of anaerobic microorganisms. Overall, the results demonstrate high potential of Mo132 and metronidazole-loaded PMMA scaffold for guided bone regeneration/guided tissue regeneration.

Regulation of Antimicrobial Effect of Hemicyanine-Based Photosensitizer via Supramolecular Assembly.

An intelligent “antimicrobial switch” has been constructed to reduce prolonged exposure of pathogenic bacteria to antibiotics, which could reversibly “turn off” or “turn on” the antimicrobial activity of hemicyanines through self-assembly or dis-assembly of cucurbit[7]uril (CB[7]). This assembly effectively inhibited the production of ROS under light, shielding the active site of hemicyanines and achieving on-demand antimicrobial ability. Moreover, CB[7] differentially inhibits ROS of molecules with different alkyl chain lengths, which provided reference for the subsequent design of materials with antimicrobial activity regulation, and could effectively delay or even prevent the development of pathogens resistance.

Biocontrol potential of Bacillus velezensis EM-1 associated with suppressive rhizosphere soil microbes against tobacco bacterial wilt.

Tobacco bacterial wilt caused by Ralstonia solanacearum is one of the most devastating diseases. Microbial keystone taxa were proposed as promising targets in plant disease control. In this study, we obtained an antagonistic Bacillus isolate EM-1 from bacterial wilt-suppressive soil, and it was considered rhizosphere-resident bacteria based on high (100%) 16S rRNA gene similarity to sequences derived from high-throughput amplicon sequencing. According to 16S rRNA gene sequencing and MLSA, strain EM-1 was identified as Bacillus velezensis. This strain could inhibit the growth of R. solanacearum, reduce the colonization of R. solanacearum in tobacco roots, and decrease the incidence of bacterial wilt disease. In addition, strain EM-1 also showed a strong inhibitory effect on other phytopathogens, such as Alternaria alternata and Phytophthora nicotianae, indicating a wide antagonistic spectrum. The antimicrobial ability of EM-1 can be attributed to its volatile, lipopeptide and polyketide metabolites. Iturin A (C14, C15, and C16) was the main lipopeptide, and macrolactin A and macrolactin W were the main polyketides in the fermentation broth of EM-1, while heptanone and its derivatives were dominant among the volatile organic compounds. Among them, heptanones and macrolactins, but not iturins, might be the main potential antibacterial substances. Complete genome sequencing was performed, and the biosynthetic gene clusters responsible for iturin A and macrolactin were identified. Moreover, strain EM-1 can also induce plant resistance by increasing the activity of CAT and PPO in tobacco. These results indicated that EM-1 can serve as a biocontrol Bacillus strain for tobacco bacterial wilt control. This study provides a better insight into the strategy of exploring biocontrol agent based on rhizosphere microbiome.

Comparison and selection of probiotic Lactobacillus from human intestinal tract and traditional fermented food in vitro via PCA, unsupervised clustering algorithm, and heat-map analysis.

Traditional fermented products and human intestines are rich sources of Lactobacillus strains which may have remarkable probiotic properties. In the present study, the probiotic properties of 40 Lactobacillus strains isolated from intestinal tracts of longevity population and traditional fermented food in China were determined, including the survival rates in simulated gastric acid and bile salt, aggregation, hydrophobicity, adhesion rate, antioxidant ability (ferric reducing antioxidant power), and antimicrobial ability. The differences between human strains and nonhuman strains were compared via t-test and principal component analysis (PCA). The significant differences were found in the survival rate at 0.3% bile salt, adhesion ability of the strains, and antioxidant ability of the fermentation broth (p < .05). The results of PCA showed that the first principal component (PC1) score of human strains was significantly higher than that of nonhuman strains (p < .01). And some probiotic Lactobacillus were selected for further application based on the unsupervised clustering algorithm, heat-map analysis, and K-means algorithm. Four strains, CS128, CS39, CS01, and CS1301, along with Lactobacillus rhamnosus GG (LGG) were divided into cluster I. The four strains, all isolated from human tracts, have been selected. Thus, human Lactobacillus has better probiotic potential and application prospects than strains from the nonhuman source. PCA, the unsupervised clustering algorithm, and heat-map analysis can be used to analyze and select Lactobacillus visually and effectively.

Anatomo-comparative study of formaldehyde, alcohol, and saturated salt solution as fixatives in Wistar rat brains.

Although formaldehyde is the most widely used and largely available fixative for preserving cadavers through decomposition prevention, it promotes darkening and weight gain, in addition to being considered carcinogenic. Ethyl alcohol has been proven a potential substitute to formaldehyde due to its effectiveness in tissue penetration, thus preventing proliferation of microorganisms; however, it can only be used alone for fixation of small parts. In view of such fixatives limitations, saturated salt solution has been widely employed based on its antimicrobial effect and ability to maintain tissue similar to the original one, in addition to exerting no hazardous effects as there is no evaporation of harmful substances. This research aimed to observe anatomical brain behaviour submitted to formaldehyde, alcohol, and saturated salt solution as fixatives. Fixatives were tested in 15 adult Wistar rats' brain, submerged in 10ml of intended solution after removal for 4 weeks. Weight of the brains fixed in saturated salt did not change over the weeks. However, the weight of formaldehyde-fixed brains increased and the weight in alcohol-fixed brains decreased; in addition, modifications in all solutions measures were also observed. Alcohol provides a peculiar dehydrating effect as formaldehyde clearly increases the length of the pieces. Thus, since the saturated salt solution showed no important adjustment over the experimental time, it proved an efficient alternative for replacing formaldehyde and alcohol as fixative solutions of anatomical study of the brain.