Bacterial Membrane Research Articles

Multifaceted Activity of Fabimycin: Insights from Molecular Dynamics Studies on Bacterial Membrane Models.

Membranes─cells' essential scaffolds─are valid molecular targets for substances with an antimicrobial effect. While certain substances, such as octenidine, have been developed to target membranes for antimicrobial purposes, the recently reported molecule, fabimycin (F2B)─a novel agent targeting drug-resistant Gram-negative bacteria─has not received adequate attention regarding its activity on membranes in the literature. The following study aims to investigate the effects of F2B on different bacterial membrane models, including simple planar bilayers and more complex bilayer systems that mimic the Escherichia coli shell equipped with double inner and outer bilayers. Our results show that F2B exhibited more pronounced interactions with bacterial membrane systems compared to the control PC system. Furthermore, we observed significant changes in local membrane property homeostasis in both the inner and outer membrane models, specifically in the case of lateral diffusion, membrane thickness, and membrane resilience (compressibility, tilt). Finally, our results showed that the effect of F2B differed in a complex system and a single membrane system. Our study provides new insights into the multifaceted activity of F2B, demonstrating its potential to disrupt bacterial membrane homeostasis, indicating that its activity extends the currently known mechanism of FabI enzyme inhibition. This disruption, coupled with the ability of F2B to penetrate the outer membrane layers, sheds new light on the behavior of this antimicrobial molecule. This highlights the importance of the interaction with the membrane, crucial in combating bacterial infections, particularly those caused by drug-resistant strains.

Integrated Metabolomic and Transcriptomic Analysis Reveals the Underlying Antibacterial Mechanisms of the Phytonutrient Quercetin-Induced Fatty Acids Alteration in Staphylococcus aureus ATCC 27217

The utilization of natural products in food preservation represents a promising strategy for the dual benefits of controlling foodborne pathogens and enhancing the nutritional properties of foods. Among the phytonutrients, flavonoids have been shown to exert antibacterial effects by disrupting bacterial cell membrane functionality; however, the underlying molecular mechanisms remain elusive. In this study, we investigated the effect of quercetin on the cell membrane permeability of Staphylococcus aureus ATCC 27217. A combined metabolomic and transcriptomic approach was adopted to examine the regulatory mechanism of quercetin with respect to the fatty acid composition and associated genes. Kinetic analysis and molecular docking simulations were conducted to assess quercetin’s inhibition of β-ketoacyl-acyl carrier protein reductase (FabG), a potential target in the bacterial fatty acid biosynthesis pathway. Metabolomic and transcriptomic results showed that quercetin increased the ratio of unsaturated to saturated fatty acids and the levels of membrane phospholipids. The bacteria reacted to quercetin-induced stress by attempting to enhance fatty acid biosynthesis; however, quercetin directly inhibited FabG activity, thereby disrupting bacterial fatty acid biosynthesis. These findings provide new insights into the mechanism of quercetin’s effects on bacterial cell membranes and suggest potential applications for quercetin in bacterial inhibition.

Simultaneous Biofilm Disruption, Bacterial Killing, and Inflammation Elimination for Wound Treatment Using Silver Embellished Polydopamine Nanoplatform.

Due to the presence of spatial barriers, persistent bacteria, and excessive inflammation in bacteria biofilm-infected wounds, current nanoplatforms cannot effectively address these issues simultaneously during the therapeutic process. Herein, a novel biomimetic photothermal nanoplatform integrating silver and polydopamine nanoparticles (Ag/PDAs) that can damage biofilms, kill bacterial persisters, and reduce inflammation for wound treatment is presented. These findings reveal that Ag/PDAs exhibit a broad-spectrum antimicrobial activity through direct damage to the bacterial membrane structure. Additionally, Ag/PDAs demonstrate a potent photothermal conversion efficiency. When combined with near-infrared (NIR) irradiation, Ag/PDAs effectively disrupt the spatial structure of biofilms and synergistically eradicate the resident bacteria. Furthermore, Ag/PDAs show remarkable anti-inflammatory properties in counteracting bacterium-induced macrophage polarization. The in vivo results confirm that the topical application of Ag/PDAs significantly suppress Staphylococcus aureus biofilm-infected wounds in murine models, concurrently facilitating wound healing. This research provides a promising avenue for the eradication of bacterial biofilms and the treatment of biofilm-infected wounds.

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.

Acorus calamus L. rhizome extract and its bioactive fraction exhibits antibacterial effect by modulating membrane permeability and fatty acid composition.

Ethnopharmacological relevanceIndia's ancient texts, the Charak Samhita and Sushruta Samhita, make reference to the traditional medicinal usage of Acorus calamus L. In India and China, it has long been used to cure stomach aches, cuts, diarrhea, and skin conditions. This ability of the rhizome is attributed to its antimicrobial properties. Research studies to date have shown its antimicrobial properties. However, scientific evidence on its mode of action is still lacking. Aim of the studyAcorus calamus L. rhizome extract and its bioactive fraction exhibits antibacterial effect by modulating membrane permeability and fatty acid composition. Material and methodThe secondary metabolites in the rhizome of A. calamus L. were extracted in hexane using Soxhlet apparatus. The ability of the extract to inhibit multidrug resistant bacterial isolates, namely Bacillus cereus, Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa were evaluated using checkerboard assay. Further, the extract was purified using thin layer chromatography, gravity column chromatography, and combiflash chromatography. Structure elucidation of the active compound was done using GC-MS, FT-IR, and UV–Vis spectral scan. The mode of action of the bioactive fraction was determined. Bacterial membrane damage was analyzed using SEM, membrane permeability was determined using SYBR green I and PI dye, leakage of cytoplasmic contents were analyzed using Bradford assay and Fehling’s reagent. The ability to inhibit efflux pump of A. baumannii was determined using EtBr accumulation assay and β-lactamase inhibition was analyzed using nitrocefin as substrate. Also, the biofilm inhibition of B. cereus was determined using crystal violet dye. Moreover, the effect of the bioactive fraction on the fatty acid profile of the bacterial membrane was determined by GC-FAME analysis using 37 component FAME mix as standard. ResultsAcorus calamus L. rhizome hexane extract (AC-R-H) demonstrated broad-spectrum antibacterial activity against all the isolates tested. AC-R-H extract also significantly reduced the MIC of ampicillin against all tested bacteria, indicating its bacterial resistance modulating properties. The assay guided purification determined Asarone as the major compound present in the bioactive fraction (S-III-BAF). S-III-BAF was found to reduce the MIC of ampicillin against Escherichia coli (100–25 mg/mL), Pseudomonas aeruginosa (15–3.25 mg/mL), Acinetobacter baumannii (12.5–1.56 mg/ml), and Bacillus cereus (10–1.25 mg/mL). Further, it recorded synergistic activity with ampicillin against B. cereus (FICI = 0.365), P. aeruginosa (FICI = 0.456), and A. baumannii (FICI = 0.245). The mode of action of S-III-BAF can be attributed to its ability to disturb the membrane integrity, enhance membrane permeability, reduce biofilm formation, and possibly alter the fatty acid composition of the bacterial cell membranes. ConclusionThe bioactive fraction of AC-R-H extract containing Asarone as the active compound showed antibacterial activity and synergistic interactions with ampicillin against the tested bacterial isolates. Such activity can be attributed to the modulation of fatty acids present in bacterial membranes, which enhances membrane permeability and causes membrane damage.

Multivalent antibacterial agent based on self-assembled glycocluster of mannose-perylene-spermine conjugate for enhanced wound healing

Bacterial infection and the increasing resistance of bacteria to commercially available antibiotics have long become a threat to global human health. Therefore, it is an urgent scientific issue to explore nonantibiotic antibacterials. In this paper, a mannose-decorated spermine derivative (PBI-spm-Man) was synthesized, which formed a self-assembled glycocluster with multivalent mannose moieties and concentrated cations. PBI-spm-Man as a nonantibiotic antibacterial agent showed potent antibacterial activity towards Escherichia coli (E. coli) through both mannose-FimH targeting and non-specific electrostatic interaction and functioned by damaging bacterial membrane. PBI-spm-Man also demonstrated antibacterial activity against representative Gram-positive bacteria Staphylococcus aureus (S. aureus) and intrinsically resistant bacteria Pseudomonas aeruginosa (P. aeruginosa). What is more exciting is that PBI-spm-Man could eliminate three clinical-isolated E. coli strains that are resistant to different antibiotics at around 20 μM. In vivo full-thickness wound healing results showed that the self-assembly of PBI-spm-Man not only reduced the residual bacteria at the wound site, but also promoted wound healing. This work represents a universal design strategy for nonantibiotic antibacterial agents based on multivalent glycoconjugates.

Metabolomics unveil key pathways underlying the synergistic activities of aztreonam and avibactam against multidrug-resistant Escherichia coli.

Aztreonam/avibactam is effective against serious infections caused by Gram-negative bacteria including Enterobacterales harboring metallo-β-lactamases. While the utility of this combination has been established in vitro and in clinical trials, the purpose of this study is to enhance our understanding of the underlying mechanism responsible for their activities through metabolomic profiling of a multidrug-resistant Escherichia coli clinical isolate. Metabolomic analyses of time-dependent changes in endogenous bacterial metabolites in a clinical isolate of a multidrug-resistant E. coli treated with aztreonam and avibactam were performed. E. coli metabolomes were compared at 15min, 1h and 24h following treatments with either avibactam (4mg/L), aztreonam (4mg/L), or aztreonam (4mg/L) + avibactam (4mg/L). Drug treatment affected 326 metabolites with magnitude changes of at least 2-fold, most of which are involved primarily in peptidoglycan biosynthesis, nucleotide metabolism, and lipid metabolism.The feedstocks for peptidoglycan synthesis were depleted by aztreonam/avibactam combination;a significant downstream increase in nucleotide metabolites and a release of lipids were observed at the three timepoints. The findings indicate that the aztreonam/avibactam combination accelerates structural damage to the bacterial membrane structure and their actions were immediate and sustained compared to aztreonam or avibactam alone. By inhibiting the production of crucial cell wall precursors, the combination may have inflicted damages on bacterial DNA.

Design of Novel Saposin-like Bacteriocins Using a Hybrid Approach.

A multitude of approaches will be required to respond to the threat posed by the emergence and spread of antibiotic resistant pathogens. Bacteriocins have gained increasing attention as a possible alternative to antibiotics, as such peptide antimicrobials have mechanisms of action different from antibiotics and are therefore equally potent against antibiotic resistant bacteria as their susceptible counterparts. A group of bacteriocins known as saposin-like bacteriocins is believed to act directly on the bacterial membrane. Based on seven saposin-like leaderless bacteriocins, we have constructed a library of hybrid peptides containing all combinations of the N- and C-terminal halves of the native bacteriocins. All hybrid peptides were synthesized using in vitro protein expression and assayed for antimicrobial activity towards several pathogens. Of the 42 hybrid peptides, antimicrobial activity was confirmed for 11 novel hybrid peptides. Furthermore, several of the hybrid peptides exhibited altered antimicrobial spectra and apparent increase in potency compared to the peptides from which they were derived. The most promising hybrid, termed ISP26, was then obtained synthetically and shown to inhibit most of the Gram-positive species tested, including opportunistic pathogens and food spoilage bacteria. Additionally, ISP26 was shown to inhibit Acinetobacter, a species of Gram-negative bacteria frequently isolated from nosocomial infections. The activity of the hybrid library provides valuable insights into the design and screening of new active bacteriocins.

Synthesis of inverse push-pull coumarin dyes and their application as solvatochromic probes and labelling agents for bacterial cell membranes

Coumarin derivatives have been widely employed across a great number of applications, such as laser dyes, bioimaging or chemossensors, owing to their strong fluorescence and high-quantum yields. These properties are highly tunable through structural modification, namely by the inclusion of electron-withdrawing groups (EWG) and electron-donating groups (EDG) at positions 3 and 7 of the coumarin scaffold, respectively. Comparatively, there aren't many reports of EDGs being employed at position 3, prompting us to investigate this new class of potential fluorophores.We undertook the synthesis of three novel ethynyl-linked aminophenyl-coumarin dyes, employing a key Sonogashira-coupling reaction to introduce the electron-rich tertiary aniline moiety. Two different amine donors were used, diphenylamino (coumarins A and B) and dimethylamino (coumarin C), as well as two alkoxy substituents, dibenzyloxy (A and C) and methylenedioxy (B), in the phenyl ring of the coumarin. All dyes show strong emission and significant positive solvatochromism. Additionally, they were employed as staining agents for the cellular membrane of S. pneumoniae, a Gram-positive bacterial pathogen. None of the three derivatives presented cytotoxic effects. Only A and B successfully labelled the bacterial membrane. In the case of B a very similar staining pattern and performance to that of standard dye Nile Red was observed, while A seemed to possess a more selective distribution.

Antimicrobial effect of plasma-activated water combined with tartaric acid against Staphylococcus aureus and its application on fresh-cut asparagus lettuce

Plasma-activated water (PAW) is increasingly recognized for its role in mitigating microbial contamination in fresh-cut produce, but its disinfection effectiveness can be limited under certain conditions. Notably, dissolving organic acids in PAW is an effective way to boost its antimicrobial properties through a synergistic effect. This study examined the enhanced antimicrobial efficacy of PAW when combined with tartaric acid against Staphylococcus aureus and its application on fresh-cut asparagus lettuce. Results demonstrated that PAW combined with tartaric acid showed stronger antimicrobial efficacy than PAW alone (p < 0.05). The addition of tartaric acid to PAW increased the oxidation-reduction potential and lowered the pH, contributing to its superior antimicrobial performance against S. aureus. The underlying antimicrobial mechanisms included the inactivation of Ca2+-Mg2+-ATPase and Na+-K+-ATPase accompanied by damage to bacterial cell membrane, enhanced oxidative damage due to the influx of extracellular reactive oxygen species such as H2O2, the disrupted energy metabolic activities, and the mitigated bacterial defense system constructed by antioxidant enzymes, such as superoxide dismutase and catalase. Furthermore, the synergistic treatment improved the quality of fresh-cut asparagus lettuce by retarding browning, curbing microbial spoilage, and lessening weight loss. The preservation of color was largely due to the decreased activities of polyphenol oxidase and peroxidase, along with controlled chlorophyll degradation. These findings suggest that PAW enhanced with tartaric acid could be a promising, cost-effective disinfection strategy for fresh-cut asparagus lettuce.

Computational Design of Cyclic Peptide Inhibitors of a Bacterial Membrane Lipoprotein Peptidase.

There remains a critical need for new antibiotics against multi-drug-resistant Gram-negative bacteria, a major global threat that continues to impact mortality rates. Lipoprotein signal peptidase II is an essential enzyme in the lipoprotein biosynthetic pathway of Gram-negative bacteria, making it an attractive target for antibacterial drug discovery. Although natural inhibitors of LspA have been identified, such as the cyclic depsipeptide globomycin, poor stability and production difficulties limit their use in a clinical setting. We harness computational design to generate stable de novo cyclic peptide analogues of globomycin. Only 12 peptides needed to be synthesized and tested to yield potent inhibitors, avoiding costly preparation of large libraries and screening campaigns. The most potent analogues showed comparable or better antimicrobial activity than globomycin in microdilution assays against ESKAPE-E pathogens. This work highlights computational design as a general strategy to combat antibiotic resistance.

Metal-polyphenol coordination nanosheets with synergistic peroxidase-like and photothermal properties for efficient antibacterial treatment

Bacterial infections pose a serious threat to human health and socioeconomics worldwide. In the post-antibiotic era, the development of novel antimicrobial agents remains a challenge. Polyphenols are natural compounds with a variety of biological activities such as intrinsic antimicrobial activity and antioxidant properties. Metal-polyphenol obtained by chelation of polyphenol ligands with metal ions not only possesses efficient antimicrobial activity but also excellent biocompatibility, which has great potential for application in biomedical and food packaging fields. Herein, we developed metal-polyphenol coordination nanosheets named copper oxidized tannic acid quinone (CuTAQ) possessing efficient antibacterial and anti-biofilm effects, which was synthesized by a facile one-pot method. The synthesis was achieved by chelation of partially oxidized tannic acid (TA) with Cu2+ under mild conditions, which supports low-cost and large-scale production. It was demonstrated that CuTAQ exhibited high antibacterial activity via disrupting the integrity of bacterial cell membranes, inducing oxidative stress, and interfering with metabolism. In addition, CuTAQ exhibits excellent peroxidase catalytic activity and photothermal conversion properties, which play a significant role in enhancing its bactericidal and biofilm scavenging abilities. This study provides insights for rational design of innovative metal-polyphenol nanomaterials with efficient antimicrobial properties.

Specific discrimination of pathogenic bacteria causing septic arthritis using Raman spectroscopy: In-vitro study

In this study we performed preliminary experiments using Raman spectroscopy as an evolving technology in biofluid and microbial characterization, to explore its potential for rapid diagnosis of pathogenic bacteria in an in-vitro synovial fluid infection model. Normal human synovial fluids samples were collected from patients undergoing knee surgery and the three most common pathogenic bacteria introduced in-vitro into the samples. The bacterial growth was systematically monitored using a Raman spectroscopy. Multivariate regression analysis of acquired spectra showed bacterial characteristic Raman bands related to bacterial cell membranes and DNA structures to increase continuously as the incubation period was increased. Spectra signature recorded from cultured synovial fluid samples showed a significant loss in synovial quality and protein morphology over time compared to control samples. In this study, Raman spectroscopy shows promise for rapid pathogenic bacteria identification in synovial fluid. Marker peaks distinguished inoculated bacteria, while chemical changes reveal infection dynamics.

Photoactive polymer coatings for antibacterial applications

Because bacteria can readily induce illnesses in the human body, research into new bactericidal approaches remains relevant to the global community. Photoactive materials (e.g., photocatalysts) provide an environmentally-friendly method for killing bacteria with light. By means of light-mediated reactive oxygen generation, photocatalysts are capable of disrupting bacterial membranes. Much research on antibacterial surfaces has focused on planar substrates or physisorbed coatings, which often provide small active surface areas and limited surface-to-volume ratios, and thereby create a need for new design strategies to incorporate photocatalysts onto more scalable supports. To this end, this contribution describes the synthesis of particle-tethered polymer brush coatings, crosslinked with the organic photocatalyst tetrakis(4-carboxyphenyl)porphyrin (TCPP). Successful engineering on SiO2 surfaces was confirmed using X-ray photoelectron spectroscopy, tensiometry, and ellipsometry. Singlet oxygen (1O2) generation was confirmed through dimethyl sulfoxide oxidation experiments under visible (blue) light and bactericidal activity against Escherichia coli was verified through live/dead assays and cell viability tests.

Novel pentafluorosulfanyl-containing triclocarban analogs selectively kill Gram-positive bacteria.

The rise of antibiotic resistance among bacterial pathogens poses a significant threat to global health, underscoring the urgent need for novel antimicrobial agents. This study presents research on a promising class of novel compounds with potent antibacterial properties against Gram-positive bacteria, notably Staphylococcus aureus and MRSA. What sets these novel analogs apart is their superior efficacy at substantially lower concentrations compared with commonly used antibiotics like ciprofloxacin and gentamycin. Importantly, these compounds act by disrupting the bacterial cell membrane, offering a unique mechanism that could potentially circumvent existing resistance mechanisms. Preliminary safety assessments also highlight their potential for therapeutic use. This study not only opens new avenues for combating antibiotic-resistant infections but also underscores the importance of innovative chemical approaches in addressing the global antimicrobial resistance crisis.

Charge Effect of Mercaptobenzimidazole-Modified Ultrasmall Gold-Nanoparticles against Drug-Resistant Bacteria.

The threat of bacterial infections, especially drug-resistant strains, to human health necessitates the development of high-efficient, broad-spectrum and nonantibiotic nanodisinfectant. However, the effect of interfacial charge on the antibacterial properties of nanodisinfectant remains a mystery, which greatly limits the development of highly antibacterial active nanodisinfectant. Herein, we developed three types of ultrasmall (d < 3 nm) gold-nanoparticles (AuNPs) modified with 5-carboxylic(C)/methoxy(M)amino(A)/-2-mercaptobenzimidazole (C/M/A MB) to investigate their interfacial charge on antibacterial performance. Our results showed that both the electropositive AMB-AuNPs and electronegative CMB-AuNPs exhibited no antibacterial activity against both Gram-positive (G+) and Gram-negative (G-) bacteria. However, the electroneutral MMB-AuNPs exhibited unique antibacterial performance against both G+ and G- bacteria, even against methicillin-resistant Staphylococcus aureus (MRSA). Mechanistic investigation revealed a multipathway synergistic bacteriostatic mechanism involving MMB-AuNPs inducing damage to bacterial cell membranes, disruption of membrane potential and downregulation of ATP levels, ultimately leading to bacterial demise. Furthermore, two additional electroneutral AuNPs modified with 5-methyl-2-mercaptobenzimidazole (mMB-AuNPs) and 5-ethoxy-2-mercaptobenzimidazole (EMB-AuNPs) also demonstrated commendable antibacterial efficacy against E. coli, S. aureus, and MRSA; however, their performance was comparatively inferior to that of MMB-AuNPs. This work provides valuable insights for the development of high-performance antibacterial nanomaterials.

The CpxRA two-component system of adherent and invasive Escherichia coli contributes to epithelial cell invasion and early-stage intestinal fitness in a dysbiotic mouse model mediated by type 1 fimbriae expression.

Adherent and invasive Escherichia coli (AIEC) is a pathobiont that is involved in the onset and exacerbation of Crohn's disease. Although the inducible expression of virulence traits is a critical step for AIEC colonization in the host, the mechanism underlying AIEC colonization remains largely unclear. We here showed that the two-component signal transduction system CpxRA contributes to AIEC gut competitive colonization by activating type 1 fimbriae expression. CpxRA from AIEC strain LF82 functioned as a transcriptional regulator, as evidenced by our finding that an isogenic cpxRA mutant exhibits reduced expression of cpxP, a known regulon gene. Transcription levels of cpxP in LF82 increased in response to envelope stress, such as exposure to antimicrobials compromising the bacterial membrane, whereas the cpxRA mutant did not exhibit this response. Furthermore, we found that the cpxRA mutant exhibits less invasiveness into host cells than LF82, primarily due to reduced expression of the type 1 fimbriae. Finally, we found that the cpxRA mutant is impaired in gut competitive colonization in a mouse model. The colonization defects were reversed by the introduction of a plasmid encoding the cpxRA gene or expressing the type 1 fimbriae. Our findings indicate that modulating CpxRA activity could be a promising approach to regulating AIEC-involved Crohn's disease.

Does the Electrical Double Layer Contribute to the Mechanism of Action of Antimicrobial Peptides?

AbstractThis concept paper elucidates the possible influence of the electrical double layer (EDL) and the polyelectrolytic nature of bacterial cell walls on the behavior of antimicrobial peptides (AMPs) and lipopeptides. It proposes that the presence of EDL adjacent to lipid membranes may play a crucial role in inducing peptide aggregation and conformational changes, thus affecting their antimicrobial activity. Furthermore, it emphasizes that the negatively charged components in both Gram‐positive and Gram‐negative bacterial cell walls may act as polyelectrolytes, effectively reducing the critical micellization concentration (CMC) of positively charged peptides and lipopeptides. This reduction is expected to facilitate their aggregation, potentially enhancing their accumulation at the bacterial membrane and increasing their effectiveness in disrupting membrane integrity and exerting antimicrobial activity. Therefore, understanding the interplay between EDL effects, polyelectrolytic properties of bacterial cell walls, and the behavior of antimicrobial peptides is essential for elucidating their mechanisms of action and optimizing their therapeutic potential.

In Bacterial Membranes Lipid II Changes the Stability of Pores Formed by the Antimicrobial Peptide Nisin.

Resistance to available antibiotics poses a growing challenge to modern medicine, as this often disallows infections to be controlled. This problem can only be alleviated by the development of new drugs. Nisin, a natural lantibiotic with broad antimicrobial activity, has shown promise as a potential candidate for combating antibiotic-resistant bacteria. However, nisin is poorly soluble and barely stable at physiological pH, which despite attempts to address these issues through mutant design has restricted its use as an antibacterial drug. Therefore, gaining a deeper understanding of the antimicrobial effectiveness, which relies in part on its ability to form pores, is crucial for finding innovative ways to manage infections caused by resistant bacteria. Using large-scale molecular dynamics simulations, we find that the bacterial membrane-specific lipid II increases the stability of pores formed by nisin and that the interplay of nisin and lipid II reduces the overall integrity of bacterial membranes by changing the local thickness and viscosity.

Involvement of the Bacillus SecYEG Pathway in Biosurfactant Production and Biofilm Formation.

With Bacillus species, about 30% of extracellular proteins are translocated through the cytoplasmic membrane, coordinated by the Sec translocase. This system mainly consists of the cytoplasmic ATPase SecA and the membrane-embedded SecYEG channel. The purpose of this work was to investigate the effects of the SecYEG export system on the production of industrial biomolecules, such as biosurfactants, proteases, amylases, and cellulases. Fifty-two isolates of Bacillus species were obtained from traditional fermented foods and then characterized using molecular microbiology methods. The isolates secreted exoenzymes that included cellulases, amylases, and proteases. We present evidence that a biosurfactant-like molecule requires the SecA ATPase and the SecYEG membrane channel for its secretion. In addition, we showed that biomolecules involved in biofilm formation required the SecYEG pathway. This work presents a novel seven-target fragment multiplex PCR assay capable of identification at the species level of Bacillus through a unique SecDF chromosomal gene. The bacterial membrane protein SecDF allowed the discrimination of Bacillus subtilis, B. licheniformis, B. amyloliquefaciens, and B. sonorensis. SecA was able to interact with AprE, AmyE, and TasA. The Rose Bengal inhibitor of SecA crucially affected the interaction of AprE, AmyE, TapA, and TasA with recombinant Gst-SecA. The Rose Bengal prevented Bacillus species from secreting and producing proteases, cellulases, amylases, and biosurfactant-like molecules. It also inhibited the formation of biofilm cell communities. The data support, for the first time, that the SecYEG translocon mediates the secretion of a biosurfactant-like molecule.