Bacterial Membrane Permeability Research Articles

Magnesium implants with alternating magnetic field-enhanced hydrogen release and proton depletion for anti-infection treatment and tissue repair

Implant-related osteomyelitis is a formidable hurdle in the clinical setting and is characterized by inflammation, infection, and consequential bone destruction. Therefore, effective reactive oxygen species (ROS) scavenging, bacterial killing, and subsequent bone tissue repair are urgently needed for the treatment of difficult-to-heal osteomyelitis. Herein, we utilized the eddy-thermal effect of magnesium (Mg) implants under an alternating magnetic field (AMF) for the controlled release of H2 gas and ions (OH− and Mg2+) for the treatment of osteomyelitis. H2 released by Mg rods under AMFs effectively scavenged cytotoxic ROS, exhibiting anti-inflammatory effects and consequently disrupting the environment of bacterial infections. In addition, the OH− hindered the energy metabolism of bacteria by effectively neutralizing protons within the microenvironment. Moreover, H2 impaired the permeability of bacterial membranes and expedited the damage induced by OH−. This synergistic AMF-induced H2 and proton depletion treatment approach not only killed both gram-negative and gram-positive bacteria but also effectively treated bacterial infections (abscesses and osteomyelitis). Moreover, Mg2+ released from the Mg rods enhanced and accelerated the process of bone osteogenesis. Overall, our work cleverly exploited the eddy-thermal effect and chemical activity of Mg implants under AMFs, aiming to eliminate the inflammatory environment and combat bacterial infections by the simultaneous release of H2, OH−, and Mg2+, thereby facilitating tissue regeneration. This therapeutic strategy achieved multiple benefits in one, thus presenting a promising avenue for clinical application.

Triton X-100 enhanced antibacterial effect of photodynamic therapy against Enterococcus faecalis infection: an in vitro study

Photodynamic therapy (PDT) is an effective method for bacterial infection control in root canals of teeth with a broad-spectrum antibacterial activity. However, its application in root canal treatment is limited due to its inefficiency under hypoxic conditions and dentin staining. Triton X-100 (TX) shows great potential in enhancing the efficiency of antimicrobial agents through improving bacterial membrane permeability. The present study employed a combination of toluidine blue O (TB)-mediated PDT with TX to target the Enterococcus faecalis (E. faecalis), a bacterium with strong resistance to various antibacterial agents and mostly detected in infected root canals. PDT combined with TX showed enhanced antibacterial efficiency against both planktonic cells and biofilms of E. faecalis. At the same time, TX enhanced the antibacterial effect in dentinal tubules and reduced the incubation time. Mechanism studies revealed that TX improved reactive oxygen species (ROS) production through increasing the proportion of TB monomers. Additionally, increased membrane permeability and wettability were also observed. The findings demonstrated the PDT combined with TX could be used as a highly effective method for the root canal disinfection of teeth.

Rational design, synthesis, and antimicrobial evaluation of novel 1,2,4-trizaole-substituted 1,3,4-oxadiazole derivatives with a dual thioether moiety.

In this paper, a series of novel 1,2,4-trizaole-substituted 1,3,4-oxadiazole derivatives with a dual thioether moiety were constructed. The synthetic compounds were characterized by 1H NMR, 13C NMR, HRMS, and single crystal diffraction. The antimicrobial activities of title compounds against fungi (Pyricutaria oryzae Cav., Phomopsis sp., Botryosphaeria dothidea, cucumber Botrytis cinerea, tobacco Botrytis cinerea, blueberry Botrytis cinerea) and bacteria (Xanthomonas oryzae pv. oryzicola, Xoc; Xanthomonas axonopodis pv. citri, Xac) revealed these compounds possessed excellent antibacterial activity through mycelial growth rate method and turbidity method, respectively. Among them, compounds 7a, 7d, 7g, 7k, 7l, and 7n had the antibacterial inhibition rate of 90.68, 97.86, 93.61, 97.70, 97.26, and 92.34%, respectively. The EC50 values of 7a, 7d, 7g, 7k, 7l, and 7n were 58.31, 48.76, 58.50, 40.11, 38.15, and 46.99μg/mL, separately, superior to that of positive control pesticide thiodiazole copper (104.26μg/mL). The molecular docking simulation of compound 7l and glutathione s-transferase also confirmed its good activity. The in vivo bioassay toward Xac infected citrus leaves was also performed to evaluate the potential of compounds as efficient antibacterial reagent. Further study of antibacterial mechanism was also carried out, including extracellular polysaccharide production, permeability of bacterial membrane, and scanning electron microscope observations. The excellent antibacterial activities of these compounds provided a strong support for its application for preventing and control plant diseases.

Polydopamine-Coated Copper-Doped Co3O4 Nanosheets Rich in Oxygen Vacancy on Titanium and Multimodal Synergistic Antibacterial Study.

Medical titanium-based (Ti-based) implants in the human body are prone to infection by pathogenic bacteria, leading to implantation failure. Constructing antibacterial nanocoatings on Ti-based implants is one of the most effective strategies to solve bacterial contamination. However, single antibacterial function was not sufficient to efficiently kill bacteria, and it is necessary to develop multifunctional antibacterial methods. This study modifies medical Ti foils with Cu-doped Co3O4 rich in oxygen vacancies, and improves their biocompatibility by polydopamine (PDA/Cu-Ov-Co3O4). Under near-infrared (NIR) irradiation, nanocoatings can generate •OH and 1O2 due to Cu+ Fenton-like activity and a photodynamic effect of Cu-Ov-Co3O4, and the total reactive oxygen species (ROS) content inside bacteria significantly increases, causing oxidative stress of bacteria. Further experiments prove that the photothermal process enhances the bacterial membrane permeability, allowing the invasion of ROS and metal ions, as well as the protein leakage. Moreover, PDA/Cu-Ov-Co3O4 can downregulate ATP levels and further reduce bacterial metabolic activity after irradiation. This coating exhibits sterilization ability against both Escherichia coli and Staphylococcus aureus with an antibacterial rate of ca. 100%, significantly higher than that of bare medical Ti foils (ca. 0%). Therefore, multifunctional synergistic antibacterial nanocoating will be a promising strategy for preventing bacterial contamination on medical Ti-based implants.

Phthalates Boost Natural Transformation of Extracellular Antibiotic Resistance Genes through Enhancing Bacterial Motility and DNA Environmental Persistence.

The environmental dissemination of extracellular antibiotic resistance genes (eARGs) in wastewater and natural water bodies has aroused growing ecological concerns. The coexisting chemical pollutants in water are known to markedly affect the eARGs transfer behaviors of the environmental microbial community, but the detailed interactions and specific impacts remain elusive so far. Here, we revealed a concentration-dependent impact of dimethyl phthalate (DMP) and several other types of phthalate esters (common water pollutants released from plastics) on the natural transformation of eARGs. The DMP exposure at an environmentally relevant concentration (10 μg/L) resulted in a 4.8-times raised transformation frequency of Acinetobacter baylyi but severely suppressed the transformation at a high concentration (1000 μg/L). The promotion by low-concentration DMP was attributed to multiple mechanisms, including increased bacterial mobility and membrane permeability to facilitate eARGs uptake and improved resistance of the DMP-bounded eARGs (via noncovalent interaction) to enzymatic degradation (with suppressed DNase activity). Similar promoting effects of DMP on the eARGs transformation were also found in real wastewater and biofilm systems. In contrast, higher-concentration DMP suppressed the eARGs transformation by disrupting the DNA structure. Our findings highlight a potentially underestimated eARGs spreading in aquatic environments due to the impacts of coexisting chemical pollutants and deepen our understanding of the risks of biological-chemical combined pollution in wastewater and environmental water bodies.

Antimicrobial peptide thanatin fused endolysin PA90 (Tha-PA90) for the control of Acinetobacter baumannii infection in mouse model

BackgroundThis study addresses the urgent need for infection control agents driven by the rise of drug-resistant pathogens such as Acinetobacter baumannii. Our primary aim was to develop and assess a novel endolysin, Tha-PA90, designed to combat these challenges.MethodsTha-PA90 incorporates an antimicrobial peptide (AMP) called thanatin at its N-terminus, enhancing bacterial outer membrane permeability and reducing host immune responses. PA90 was selected as the endolysin component. The antibacterial activity of the purified Tha-PA90 was evaluated using an in vitro colony-forming unit (CFU) reduction assay and a membrane permeability test. A549 cells were utilized to measure the penetration into the cytosol and the cytotoxicity of Tha-PA90. Finally, infection control was monitored in A. baumannii infected mice following the intraperitoneal administration of Tha-PA90.ResultsTha-PA90 demonstrated remarkable in vitro efficacy, completely eradicating A. baumannii strains, even drug-resistant variants, at a low concentration of 0.5 μM. Notably, it outperformed thanatin, achieving only a < 3-log reduction at 4 μM. Tha-PA90 exhibited 2–3 times higher membrane permeability than a PA90 and thanatin mixture or PA90 alone. Tha-PA90 was found within A549 cells' cytosol with no discernible cytotoxic effects. Furthermore, Tha-PA90 administration extended the lifespan of A. baumannii-infected mice, reducing bacterial loads in major organs by up to 3 logs. Additionally, it decreased proinflammatory cytokine levels (TNF-α and IL-6), reducing the risk of sepsis from rapid bacterial lysis. Our findings indicate that Tha-PA90 is a promising solution for combating drug-resistant A. baumannii. Its enhanced efficacy, low cytotoxicity, and reduction of proinflammatory responses render it a potential candidate for infection control.ConclusionsThis study underscores the significance of engineered endolysins in addressing the pressing challenge of drug-resistant pathogens and offers insights into improved infection management strategies.

Biopesticide potential of Anisomeles indica Kuntze leaf essential oil and its nanoemulsion against bacterial blight - Xanthomonas strains

The objective of this study was to examine the chemical composition of essential oil A. indica leaves and its nanoemulsion, and evaluation of potential for use as a biopesticide. Essential oil of A. indica extracted from fresh leaves was found to be 99.97% composed of 59 components, according to GC-MS analysis. A non-ionic surfactant Tween 80 and the essential oil of A. indica were combined to create a stable nanoemulsion using sonication method. A long durable stable nanoemulsion was obtained after thirty minutes of sonication, and it was examined using TEM (Transmission electron microscopy), DLS (Dynamic light scattering), and FTIR (Fourier transform infrared spectroscopy) analyses. To consider its practical applications, other factors such as stability, viscosity, pH, turbidity, and creaming index were also investigated. Antibacterial properties of essential oil and nanoemulsion were evaluated against bacterial blight plant pathogens Xanthomonas oryzae and Xanthomonas citri. The MIC (Minimum inhibitory concentration) was determined using the broth microdilution method, and the anti-Xanthomonas activity was assessed utilizing by agar disc diffusion method. Using the crystal violet (CV) technique, inhibition of biofilm formation and development were evaluated. Disturbance of bacterial membrane permeability was confirmed by estimating the proteins and nucleic acids (DNA, and RNA) leakage from the cell membrane. Greenhouse studies using rice/paddy plants were conducted to demonstrate the antibacterial potential of essential oil and nanoemulsion, using RNR-15048 rice cultivar by seed treatment and foliar spray groups. Results of the investigations suggest that, when the essential oil was transformed into a nanoemulsion, its antibacterial effect against bacteria was significantly increased, that might be attributed to the essential oil enhanced ability to penetrate the bacterial cells. Essential oil of A. indica and its nanoemulsion reduced rice bacterial blight disease by 84%and pathogen-virulence by 92%, and promoted the growth and development of rice/paddy seedlings. These results confirm that A. indica essential oil and its nanoemulsion possess anti-bacterial blight properties, without affecting growth and development of host plants. Essential oil of A. indica and its nanoemulsion could be used as biopesticide to control Xanthomonas induced bacterial blight diseases in crop plants either by using for seed treatment or as a foliar spray.

Alkylated EDTA potentiates antibacterial photodynamic activity of protoporphyrin

Antibiotic resistance has garnered significant attention due to the scarcity of new antibiotics in development. Protoporphyrin IX (PpIX)-mediated photodynamic therapy shows promise as a novel antibacterial strategy, serving as an alternative to antibiotics. However, the poor solubility of PpIX and its tendency to aggregate greatly hinder its photodynamic efficacy. In this study, we demonstrate that alkylated EDTA derivatives (aEDTA), particularly C14-EDTA, can enhance the solubility of PpIX by facilitating its dispersion in aqueous solutions. The combination of C14-EDTA and PpIX exhibits potent antibacterial activity against Staphylococcus aureus (S. aureus) when exposed to LED light irradiation. Furthermore, this combination effectively eradicates S. aureus biofilms, which are known to be strongly resistant to antibiotics, and demonstrates high therapeutic efficacy in an animal model of infected ulcers. Mechanistic studies reveal that C14-EDTA can disrupt PpIX crystallization, increase bacterial membrane permeability and sequester divalent cations, thereby improving the accumulation of PpIX in bacteria. This, in turn, enhances reactive oxygen species (ROS) production and the antibacterial photodynamic activity. Overall, this effective strategy holds great promise in combating antibiotic-resistant strains.Graphical

Design, synthesis, anti-infective potency and mechanism study of novel Ru-based complexes containing substituted adamantane as antibacterial agents

Infections caused by Staphylococcus aureus (S. aureus) are increasing difficult to treat because this pathogen is easily resistant to antibiotics. However, the development of novel antibacterial agents with high antimicrobial activity and low frequency of resistance remains a huge challenge. Here, building on the coupling strategy, an adamantane moiety was linked to the membrane-active Ru-based structure and then developed three novel metalloantibiotics: [Ru(bpy)2(L)](PF6)2 (Ru1) (bpy = 2,2-bipyridine, L = amantadine modified ligand), [Ru(dmb)2(L)](PF6)2 (Ru2) (dmb = 4,4′-dimethyl-2,2′-bipyridine) and [Ru(dpa)2(L)](PF6)2 (Ru3), (dpa = 2,2′-dipyridylamine). Notably, complex Ru1 was identified to be the best candidate agent, showing greater efficacy against S. aureus than most of clinical antibiotics and low resistance frequencies. Mechanism studies demonstrated that Ru1 could not only increase the permeability of bacterial cell membrane and then caused the leakage of bacterial contents, but also promoted the production of reactive oxygen species (ROS) in bacteria. Importantly, complex Ru1 inhibited the biofilm formation, exotoxin secretion and increased the potency of some clinical used antibiotics. In addition, Ru1 showed low toxic in vivo and excellent anti-infective efficacy in two animal infection model. Thus, Ru-based metalloantibiotic bearing adamantane moiety are promising antibacterial agents, providing a certain research basis for the future antibiotics research.

Synthesis, Structural Characterization, and Biological Activities of 1,3,4- Thiadiazole Derivatives Containing Sulfonylpiperazine Structures.

To develop novel bacterial biofilm inhibiting agents, a series of 1,3,4-thiadiazole derivatives containing sulfonylpiperazine structures were designed, synthesized, and characterized using 1H nuclear magnetic resonance (1H NMR), 13C nuclear magnetic resonance (13C NMR), and high-resolution mass spectrometry. Meanwhile, their biological activities were evaluated, and the ensuing structure-activity relationships were discussed. The bioassay results showed the substantial antimicrobial efficacy exhibited by most of the compounds. Among them, compound A24 demonstrated a strong efficacy with an EC50 value of 7.8 μg/mL in vitro against the Xanthomonas oryzae pv. oryzicola (Xoc) pathogen, surpassing commercial agents thiodiazole copper (31.8 μg/mL) and bismerthiazol (43.3 μg/mL). Mechanistic investigations into its anti-Xoc properties revealed that compound A24 operates by increasing the permeability of bacterial cell membranes, inhibiting biofilm formation and cell motility, and inducing morphological changes in bacterial cells. Importantly, in vivo tests showed its excellent protective and curative effects on rice bacterial leaf streak. Besides, molecular docking showed that the hydrophobic effect and hydrogen-bond interactions are key factors between the binding of A24 and AvrRxo1-ORF1. Therefore, these results suggest the utilization of 1,3,4-thiadiazole derivatives containing sulfonylpiperazine structures as a bacterial biofilm inhibiting agent, warranting further exploration in the realm of agrochemical development.

A Fluorous Peptide Amphiphile with Potent Antimicrobial Activity for the Treatment of MRSA-induced Sepsis and Chronic Wound Infection.

The rising prevalence of global antibiotic resistance evokes the urgent need for novel antimicrobial candidates. Cationic lipopeptides have attracted much attention due to their strong antimicrobial activity, broad-spectrum and low resistance tendency. Herein, a library of fluoro-lipopeptide amphiphiles was synthesized by tagging a series of cationic oligopeptides with a fluoroalkyl tail via a disulfide spacer. Among the lipopeptide candidates, R6F bearing six arginine moieties and a fluorous tag shows the highest antibacterial activity, and it exhibits an interesting fluorine effect as compared to the non-fluorinated lipopeptides. The high antibacterial activity of R6F is attributed to its excellent bacterial membrane permeability, which further disrupts the respiratory chain redox stress and cell wall biosynthesis of the bacteria. By co-assembling with lipid nanoparticles, R6F showed high therapeutic efficacy and minimal adverse effects in the treatment of MRSA-induced sepsis and chronic wound infection. This work provides a novel strategy to design highly potent antibacterial peptide amphiphiles for the treatment of drug-resistant bacterial infections.

The synergistic antibacterial activity and mechanism of colistin-oxethazaine combination against gram-negative pathogens.

The rapid spread of bacteria with plasmid-mediated resistance to antibiotics poses a serious threat to public health. The search for potential compounds that can increase the antibacterial activity of existing antibiotics is a promising strategy for addressing this issue. Synergistic activity of the FDA-approved agent oxethazine combined with colistin was investigated in vitro using checkerboard assays and time-kill curves. The synergistic mechanisms of their combination of oxethazine and colistin was explored by fluorescent dye, scanning electron microscopy (SEM) and LC-MS/MS. The synergistic efficacy was evaluated in vivo by the Galleria mellonella and mouse sepsis models. In this study, we found that oxethazine could effectively enhance the antibacterial activity of colistin against both mcr-positive and -negative pathogens, and mechanistic assays revealed that oxethazine could improve the ability of colistin to destruct bacterial outer membrane and cytoplasmic membrane permeability. In addition, their combination triggered the accumulation of reactive oxygen species causing additional damage to the membrane structure resulting in cell death. Furthermore, oxethazine significantly enhanced the therapeutic efficacy of colistin in two animal models. These results suggested that oxethazine, as a promising antibiotic adjuvant, can effectively enhance colistin activity, providing a potential strategy for treating multidrug-resistant bacteria.

Study on synergistic mechanism of molybdenum disulfide/sodium carboxymethyl cellulose composite nanofiber mats for photothermal/photodynamic antibacterial treatment

Innovative antibacterial therapies using nanomaterials, such as photothermal (PTT) and photodynamic (PDT) treatments, have been developed for treating wound infections. However, creating secure wound dressings with these therapies faces challenges. The primary focus of this study is to prepare an antibacterial nanofiber dressing that effectively incorporates stable loads of functional nanoparticles and demonstrates an efficient synergistic effect between PTT and PDT. Herein, a composite nanofiber mat was fabricated, integrating spherical molybdenum disulfide (MoS2) nanoparticles. MoS2 was deposited onto polylactic acid (PLA) nanofiber mats using vacuum filtration, which was further stabilized by sodium carboxymethyl cellulose (CMC) adhesion and glutaraldehyde (GA) cross-linking. The composite nanofibers demonstrated synergistic antibacterial effects under NIR light irradiation, and the underlying mechanism was explored. They induce bacterial membrane permeability, protein leakage, and intracellular reactive oxygen species (ROS) elevation, ultimately leading to >95 % antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), which is higher than that of single thermotherapy (almost no antibacterial activity) or ROS therapy (about 80 %). In addition, the composite nanofiber mats exhibited promotion effects on infected wound healing in vivo. This study demonstrates the great prospects of composite nanofiber dressings in clinical treatment of bacterial-infected wounds.

Polystyrene nanoparticles induce biofilm formation in Pseudomonas aeruginosa

In recent years, micro/nanoplastics have garnered widespread attention due to their ecological risks. In this study, we investigated the effects of polystyrene nanoparticles (PS-NPs) of different sizes on the growth and biofilm formation of Pseudomonas aeruginosa PAO1. The results demonstrated that exposure to certain concentrations of PS-NPs significantly promoted bacterial biofilm formation. Meanwhile, we comprehensively revealed its mechanism whereby PS-NPs induced oxidative stress and altered bacterial membrane permeability by contacting or penetrating bacterial membranes. To counteract the stimulation by PS-NPs and reduce their toxicity, bacteria enhanced biofilm formation by upregulating the expression of biofilm-related genes, increasing EPS and virulence factors secretion, and enhancing bacterial motility through the participation of the quorum sensing (QS) system. Additionally, we also found that exposure to PS-NPs enhanced bacterial antibiotic resistance, posing a challenge to antimicrobial therapy. Our study reveals the toxic effects of nanoplastics and the defense mechanisms of bacteria, which has important implications for the risk assessment and management of environmental nanoplastics.

A Fluorous Peptide Amphiphile with Potent Antimicrobial Activity for the Treatment of MRSA‐induced Sepsis and Chronic Wound Infection

The rising prevalence of global antibiotic resistance evokes the urgent need for novel antimicrobial candidates. Cationic lipopeptides have attracted much attention due to their strong antimicrobial activity, broad‐spectrum and low resistance tendency. Herein, a library of fluoro‐lipopeptide amphiphiles was synthesized by tagging a series of cationic oligopeptides with a fluoroalkyl tail via a disulfide spacer. Among the lipopeptide candidates, R6F bearing six arginine moieties and a fluorous tag shows the highest antibacterial activity, and it exhibits an interesting fluorine effect as compared to the non‐fluorinated lipopeptides. The high antibacterial activity of R6F is attributed to its excellent bacterial membrane permeability, which further disrupts the respiratory chain redox stress and cell wall biosynthesis of the bacteria. By co‐assembling with lipid nanoparticles, R6F showed high therapeutic efficacy and minimal adverse effects in the treatment of MRSA‐induced sepsis and chronic wound infection. This work provides a novel strategy to design highly potent antibacterial peptide amphiphiles for the treatment of drug‐resistant bacterial infections.

Co-exposure to pentachlorophenol (PCP) and cadmium (Cd) triggers apoptosis-like cell death in Eschericia coli

Pentachlorophenol (PCP) - cadmium (Cd) complex pollution has been identified as a form of persistent soil pollution in south China, exerting detrimental impacts on the indigenous soil bacterial communities. Hence, it is worthwhile to investigate whether and how bacterial populations alter in response to these pollutants. In this study, Escherichia coli was used as a model bacterium. Results showed that PCP exposure caused bacterial cell membrane permeability changes, intracellular ROS elevation, and DNA fragmentation, and triggered apoptosis-like cell death at low exposure concentration and necrosis at high exposure concentration. Cd exposure caused severe oxidative damage and cell necrosis in the tested bacterial strain. The co-exposure to PCP and Cd elevated the ROS level, stimulated the bacterial caspase activity, and induced DNA fragmentation, thereby leading to an apoptosis-like cell death. In conclusion, PCP-Cd complex pollution can cause bacterial population to decrease through apoptosis-like cell death pathway. However, it is worth noting that the subpopulation survives under the complex pollution stress.

Rational Design of a Potent Antimicrobial Peptide Based on the Active Region of a Gecko Cathelicidin.

The emergence of multidrug-resistant (MDR) bacteria presents a significant challenge to public health, increasing the risk of infections that are resistant to current antibiotic treatment. Antimicrobial peptides (AMPs) offer a promising alternative to conventional antibiotics in the prevention of MDR bacterial infections. In the present study, we identified a novel cathelicidin AMP from Gekko japonicus, which exhibited broad-spectrum antibacterial activity against both Gram-negative and Gram-positive bacteria, with minimal inhibitory concentrations ranging from 2.34 to 4.69 μg/mL. To improve its potential therapeutic application, a series of peptides was synthesized based on the active region of the gecko-derived cathelicidin. The lead peptide (RH-16) showed an antimicrobial activity comparable to that of the parent peptide. Structural characterization revealed that RH-16 adopted an amphipathic α-helical conformation. Furthermore, RH-16 demonstrated neither hemolytic nor cytotoxic activity but effectively killed a wide range of clinically isolated, drug-resistant bacteria. The antimicrobial activity of RH-16 was attributed to the nonspecific targeting of bacterial membranes, leading to rapid bacterial membrane permeabilization and rupture. RH-16 also retained its antibacterial activity in plasma and exhibited mild toxicity in vivo. Notably, RH-16 offered robust protection against skin infection in a murine model. Therefore, this newly identified cathelicidin AMP may be a strong candidate for future pharmacological development targeting multidrug resistance. The use of a rational design approach for isolating the minimal antimicrobial unit may accelerate the transition of natural AMPs to clinically applicable antibacterial agents.

Active substances of myxobacteria against plant diseases and their action mechanisms.

Myxobacteria have a complex life cycle and unique social behavior, and obtain nutrients by preying on bacteria and fungi in soil. Chitinase, β-1,3 glucanase and β-1,6 glucanase produced by myxobacteria can degrade the glycosidic bond of cell wall of some plant pathogenic fungi, resulting in a perforated structure in the cell wall. In addition, isooctanol produced by myxobacteria can lead to the accumulation of intracellular reactive oxygen species in some pathogenic fungi and induce cell apoptosis. Myxobacteria can also perforate the cell wall of some plant pathogenic oomycetes by β-1,3 glucanase, reduce the content of intracellular soluble protein and protective enzyme activity, affect the permeability of oomycete cell membrane, and aggravate the oxidative damage of pathogen cells. Small molecule compounds such as diisobutyl phthalate and myxovirescin produced by myxobacteria can inhibit the formation of biofilm and lipoprotein of bacteria, and cystobactamids can inhibit the activity of DNA gyrase, thus changing the permeability of bacterial cell membrane. Myxobacteria, as a new natural compound resource bank, can control plant pathogenic fungi, oomycetes and bacteria by producing carbohydrate active enzymes and small molecular compounds, so it has great potential in plant disease control.

Rhein against Staphylococcus xylosus by interfering with respiratory metabolism and inducing oxidative stress

Currently, dairy mastitis caused by Staphylococcus xylosus poses a serious challenge for dairy farming. In this study, we explored the role and mechanism of rhein against S. xylosus with the hope of providing new research ideas to solve mastitis in dairy cows and ensure the source safety of dairy products. Through in vitro antimicrobial studies, we found that the minimum inhibitory concentration (MIC) of rhein was 64 μg/mL, and it significantly interfered with the formation of S. xylosus biofilm at sub-MIC. In experiments on mastitis in mice, rhein alleviated inflammation in mammary tissue, reduced the levels of TNF-α and IL-6, and decreased the number of S. xylosus. To explore the anti-S. xylosus mechanism of rhein, we identified the relevant proteins involved in carbon metabolism (Glycolysis/gluconeogenesis, TCA cycle, Fatty acid degradation) through proteomics. Additionally, proteins associated with the respiratory chain, oxidative stress (proteins of antioxidant and DNA repair), and nitrate respiration were also found to be upregulated. Thus, rhein may act as an antibacterial agent by interfering with the respiratory metabolism of S. xylosus and inducing the production of ROS, high levels of which alter the permeability of bacterial cell membranes and cause damage to them. We measured the concentrations of extracellular β-galactosidase and nucleic acids. Additionally, SEM observation of S. xylosus morphology showed elevated membrane permeability and damage to the cell membrane. Finally, RT-PCR experiments showed that mRNAs of key proteins of the TCA cycle (odhA, mqo) and nitrate respiration (nreB, nreC, narG) were significantly up-regulated, consistent with proteomic results. In conclusion, rhein has good anti-S. xylosus effects in vitro and in vivo, by interfering with bacterial energy metabolism, inducing ROS production, and causing cell membrane and DNA damage, which may be one of the important mechanisms of its antimicrobial activity.

Antibacterial, bacteriolytic, antibiofilm, and synergistic effects of Curcuma species ethanol extracts with antibiotic against multidrug resistant Pseudomonas aeruginosa

Introduction: Curcuma species have shown antibacterial activity against Pseudomonas aeruginosa. The current study was conducted to analyze the antibacterial activity of ethanol extracts of Curcuma species rhizomes, including Curcuma domestica, C. xanthorrhiza, C. mangga, C. zedoaria, and C. aeruginosa against multidrug-resistant Pseudomonas aeruginosa (MDR P. aeruginosa). Furthermore, the mechanism action of Curcuma species in combination with antibiotic against MDR P. aeruginosa and its chemical component were also investigated. Methods: Determination of minimum inhibitory concentration (MIC) was carried out by the microdilution method. The synergistic effects of the extract and tetracycline were determined by the checkerboard method. The effect of the combination of Curcuma species and tetracycline to prevent bacterial resistance was investigated using inhibition of biofilm formation, permeability of bacterial cell membrane, and EtBr accumulation methods. Gas chromatography-mass spectrometry (GC-MS) analysis was also performed. Results: MIC of C. domestica, C. xanthorrhiza, and C. mangga against MDR P. aeruginosa were 125, 250, and 125 µg/mL, respectively. C. xanthorrhiza ethanol extract (7.8 µg/mL) in combination with tetracycline (1.9 µg/mL) revealed a synergistic activity with Fractional Inhibitory Concentration Index (FICI) value of 0.06. The combination of C. xanthorrhiza ethanol extract and tetracycline showed inhibitory effects on biofilm formation and efflux pump of MDR P. aeruginosa. This combination also had bacteriolytic activity. GC-MS analysis led to the identification of ar-turmerone (11.63%) and xanthorrhizol (11.36%) as the major compounds. Conclusion: Combination of C. xanthorrhiza ethanol extract and tetracycline might be developed as an alternative treatment against MDR P. aeruginosa.