Alternative Antibacterial Strategies Research Articles

Antimicrobial Peptide‐Modified Liquid Metal Nanomaterials for Enhanced Antibacterial Photothermal Therapy

The misuse of antibiotics has led to antibiotic‐resistant “superbugs,” prompting the exploration of alternative antibacterial strategies. This study focuses on the promising avenue of photothermal therapy (PTT). Despite numerous advantages, the clinical applicability of PTT as a sole sterilization strategy is hindered by the necessity for higher temperatures, potentially causing harm to healthy tissues. To overcome this challenge, this study introduces antimicrobial peptides (AMPs) to modify the surface of gallium‐based liquid metal (LM) nano‐antimicrobial agents, thereby enhancing their photothermal antibacterial effects within a lower temperature range. First, a novel LM composite nanomaterial, LM@AMP nanoparticles, is synthesized through a sonication process involving 1,2‐distearoyl‐sn‐glycero‐3‐phosphoethanolamine‐N‐[carboxy(polyethylene glycol)], AMP, and LM in an aqueous solution. Herein, AMPs not only contribute to the structural stability of LM nanoparticles but also enhance their selective interaction with bacterial cell membranes. Then, a thorough characterization of LM@AMP nanoparticles is performed, encompassing analyses through electron microscopy, determination of particle size, and assessment of zeta potential. Moreover, the exceptional photothermal properties exhibited by these nanoparticles are validated. Finally, this investigation demonstrates that LM@AMP nanoparticles selectively target bacterial cell membranes, showcasing efficient bactericidal effects (near 100%) at relatively low temperatures under near‐infrared irradiation.

AMPActiPred: A three‐stage framework for predicting antibacterial peptides and activity levels with deep forest

AbstractThe emergence and spread of antibiotic‐resistant bacteria pose a significant public health threat, necessitating the exploration of alternative antibacterial strategies. Antibacterial peptide (ABP) is a kind of antimicrobial peptide (AMP) that has the potential ability to fight against bacteria infection, offering a promising avenue for developing novel therapeutic interventions. This study introduces AMPActiPred, a three‐stage computational framework designed to identify ABPs, characterize their activity against diverse bacterial species, and predict their activity levels. AMPActiPred employed multiple effective peptide descriptors to effectively capture the compositional features and physicochemical properties of peptides. AMPActiPred utilized deep forest architecture, a cascading architecture similar to deep neural networks, capable of effectively processing and exploring original features to enhance predictive performance. In the first stage, AMPActiPred focuses on ABP identification, achieving an Accuracy of 87.6% and an MCC of 0.742 on an elaborate dataset, demonstrating state‐of‐the‐art performance. In the second stage, AMPActiPred achieved an average GMean at 82.8% in identifying ABPs targeting 10 bacterial species, indicating AMPActiPred can achieve balanced predictions regarding the functional activity of ABP across this set of species. In the third stage, AMPActiPred demonstrates robust predictive capabilities for ABP activity levels with an average PCC of 0.722. Furthermore, AMPActiPred exhibits excellent interpretability, elucidating crucial features associated with antibacterial activity. AMPActiPred is the first computational framework capable of predicting targets and activity levels of ABPs. Finally, to facilitate the utilization of AMPActiPred, we have established a user‐friendly web interface deployed at https://awi.cuhk.edu.cn/∼AMPActiPred/.

A multifunctional guanosine-based carbon dots for dead microbial imaging and synergistic broad-spectrum antimicrobial therapy

Pathogenic microbial infection poses serious threats to human lives and antibiotic abuse leads to bacterial resistance. The development of alternative antibacterial agents and strategies with reduced resistance risk is urgently demanded. Heteroatom doping is a feasible method for adjusting the electronic and optical properties of carbon dots (CDs) to improve their bioimaging performance and light-mediated therapeutic efficiency. Herein, we synthesized a series of guanosine-derived CDs from guanosine (G), guanosine monophosphate (GMP), guanosine diphosphate (GDP), and guanosine triphosphate (GTP) as respective precursors. G-CDs, prepared by guanosine with strong surface negative charge and suitable size, can successfully differentiate and stain dead microbial cells (bacteria and fungi). G-CDs with a high N content exhibited the highest antibacterial activity in vitro and in vivo among the four guanosine-derived CDs, owing to triple synergistic antibacterial actions - the intrinsic antibacterial mechanism, bacterial photodynamic and photothermal inactivation against bacteria and fungi. In this paper, we present a promising new method to prepare CDs using natural biomolecules from living systems as precursors for multifunctional dead microbial cells imaging and broad-spectrum theranostic applications.

Ciprofloxacin loaded PEG coated ZnO nanoparticles with enhanced antibacterial and wound healing effects

Antimicrobial resistance is a worldwide health problem that demands alternative antibacterial strategies. Modified nano-composites can be an effective strategy as compared to traditional medicine. The current study was designed to develop a biocompatible nano-drug delivery system with increased efficacy of current therapeutics for biomedical applications. Zinc oxide nanoparticles (ZnO-NPs) were synthesized by chemical and green methods by mediating with Moringa olifera root extract. The ZnO–NPs were further modified by drug conjugation and coating with PEG (CIP-PEG-ZnO-NPs) to enhance their therapeutic potential. PEGylated ZnO-ciprofloxacin nano-conjugates were characterized by Fourier Transform Infrared spectroscopy, X-ray diffractometry, and Scanning Electron Microscopy. During antibacterial screenings chemically and green synthesized CIP-PEG-ZnO-NPs revealed significant activity against clinically isolated Gram-positive and Gram-negative bacterial strains. The sustainable and prolonged release of antibiotics was noted from the CIP–PEG conjugated ZnO-NPs. The synthesized nanoparticles were found compatible with RBCs and Baby hamster kidney cell lines (BHK21) during hemolytic and MTT assays respectively. Based on initial findings a broad-spectrum nano-material was developed and tested for biomedical applications that eradicated Staphylococcus aureus from the infectious site and showed wound-healing effects during in vivo applications. ZnO-based nano-drug carrier can offer targeted drug delivery, and improved drug stability and efficacy resulting in better drug penetration.

Characterization and genomic analysis of a broad-spectrum lytic phage PG288: A potential natural therapy candidate for Vibrio infections

Vibrio parahaemolyticus, an important zoonotic pathogen, can cause severe diseases and even death in aquatic animals and humans. As the widespread use of antibiotics gradually diminishes their effectiveness, phages, which can selectively lyse bacteria, are garnering increased attention as a valuable alternative antibacterial strategy. This study characterized PG288, a lytic phage utilizing V. parahaemolyticus strain G855 as its host. Morphologically, the phage features a polyhedral head and a long, non-retractable tail. Bactericidal assays revealed that phage PG288 exhibited a strong lytic ability against V. parahaemolyticus strain G855 and demonstrated a broad host range, as evidenced by the ability to infect several distinct Vibrio species. The one-step growth curve indicated a latent period of approximately 50 min for phage PG288, with a burst size of roughly 92 PFU per cell. Additionally, phage PG288 exhibited remarkable stability within a temperature range of 20–50°C and a pH range of 4–10. Genomic analysis unveiled 105 ORFs within phage PG288, notably devoid of genes associated with antibiotic resistance, virulence, and lysogenic activity. Phylogenetic analysis conclusively identified it as a new member of the genus Mardecavirus within the class Caudoviricetes. In summary, this study contributes valuable insights to the phage database, presenting phage PG288 as a promising candidate for phage therapies against Vibrio infections.

Antibacterial micro/nanomotors: current research progress, challenges, and opportunities.

Bacterial infections remain a formidable threat to human health, a situation exacerbated by the escalating problem of antibiotic resistance. While alternative antibacterial strategies such as oxidants, heat treatments, and metal nanoparticles (NPs) have shown potential, they come with significant drawbacks, ranging from non-specificity to potential environmental concerns. In the face of these challenges, the rapid evolution of micro/nanomotors (MNMs) stands out as a revolutionary development in the antimicrobial arena. MNMs harness various forms of energy and convert it into a substantial driving force, offering bright prospects for combating microbial threats. MNMs' mobility allows for swift and targeted interaction with bacteria, which not only improves the carrying potential of therapeutic agents but also narrows the required activation range for non-drug antimicrobial interventions like photothermal and photodynamic therapies, substantially improving their bacterial clearance rates. In this review, we summarized the diverse propulsion mechanisms of MNMs employed in antimicrobial applications and articulated their multiple functions, which include direct bactericidal action, capture and removal of microorganisms, detoxification processes, and the innovative detection of bacteria and associated toxins. Despite MNMs' potential to revolutionize antibacterial research, the translation from laboratory to clinical use remains challenging. Based on the current research status, we summarized the potential challenges and possible solutions and also prospected several key directions for future studies of MNMs for antimicrobial purposes. Collectively, by highlighting the important knowns and unknowns of antimicrobial MNMs, our present review would help to light the way forward for the field of antimicrobial MNMs and prevent unnecessary blindness and detours.

Antibacterial and Photocatalytic Properties of ZnO Nanostructure Decorated Coatings

Given the growing concern over antibiotic resistance, there is an urgent need to explore alternative antibacterial strategies. Metal oxide nanostructures have emerged as a promising option, and in particular, zinc oxide (ZnO) nanostructures have demonstrated strong antifungal and antibacterial properties. This study focuses on ZnO nanowires (ZnO NWs) and their potential as antibacterial agents against Pseudomonas putida, a Gram-negative bacterium. The objective is to investigate the antibacterial mechanisms and assess their efficiency. The unique shape of ZnO NWs, obtained through hydrothermal growth, may rupture bacterial cells and inhibit bacterial growth. In addition to their morphology, the release of Zn2+ ions from ZnO NWs may contribute to their antibacterial properties. These ions have the potential to disrupt the bacterial cell membrane, further impeding bacterial growth. Moreover, ZnO nanostructures exhibit excellent photocatalytic properties under UV light, enhancing their antibacterial effects. Overall, this study highlights the potential of hydrothermally synthesized ZnO NWs in inhibiting P. putida growth and provides valuable insights into their antibacterial mechanisms. The findings suggest that ZnO nanostructures have the potential to be effective antibacterial agents and could be utilized in various settings to fight microbial infections and maintain hygiene.

Synergistic effect of kanamycin and amikacin with setomimycin on biofilm formation inhibition of Listeria monocytogenes

Listeria monocytogenes, a foodborne pathogen that causes listeriosis with high fatality rate, exhibits multidrug resistance (MDR) known to be progressively increasing. Alternative antibacterial strategies are in high demand for treating this well-known pathogen. Anti-biofilm and anti-virulence strategies are being explored as novel approaches to treat bacterial infections. In this study, one rare antibacterial named setomimycin was isolated from Streptomyces cyaneochromogenes, which showed potent antibacterial activity against L. monocytogenes. Next, the inhibition of biofilm formation and listeriolysin O (LLO) production against L. monocytogenes were investigated at sub-minimal inhibitory concentrations (sub-MICs) of setomimycin alone or combined with kanamycin and amikacin. Crystal violet staining confirmed that setomimycin combining with kanamycin or amikacin could dramatically reduce biofilm formation against L. monocytogenes at sub-MICs, which was further evaluated by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). In the meantime, sub-MICs of setomimycin could significantly suppress the secretion of LLO. Furthermore, the transcription of genes associated with biofilms and main virulence factors, such as LLO, flagellum, and metalloprotease, were suppressed by setomimycin at sub-MICs. Hence, the study provided a deep insight into setomimycin as an alternative antibacterial agent against L. monocytogenes.

Energy exchange in the body of broilers when introducing Quercus cortex extract and chlortetracycline into the diet

Feed antibiotics are widely used in the diet of poultry as growth stimulants, to maintain health and increase productivity. However, their use carries some risks, which leads to a reduction in the use of antibiotics in diets. Therefore, the search for an alternative that can minimize the negative effect of antibacterial substances is a global task. Plants containing phytochemical compounds are of great interest in the search. One of such phytobiotics is oak bark (Quercus cortex), some of its components act as agents of alternative antibacterial strategies (blocking of the Quorum Sensing signaling system (QS)). However, studies on the effects of Quercus cortex are few. It is interesting to study the additional effects of this phytobiotic in combination with other biologically active substances (probiotics, enzymes and antibiotics in small doses). Based on this, the purpose of this work was to evaluate the effect of Quercus cortex extract and Biovit 200 feed antibiotic based on 20% chlortetracycline on energy metabolism in broiler chickens. The study was conducted using generally accepted methods of analyzing metabolic processes in the body of a bird. The calculation of net and exchange energies, energy protein ratio, coefficient of productive use of exchange energy, gross energy was made. The results obtained allow us to conclude that the inclusion of Quercus cortex extract at a dosage of 0,2 ml/kg both independently and in combination with Biovit 200 at a dosage of 0,63 g/kg w.m./ day contributed to a reduction in the amount of energy loss with excrement with an increase in the KPI of OE and the compliance indicator, which shows a more rational use of energy for the process of tissue synthesis in the body of birds of I and III groups.

Ligand-displaying Escherichia coli cells and minicells for programmable delivery of toxic payloads via type IV secretion systems.

The rapid emergence of drug-resistant bacteria and current low rate of antibiotic discovery emphasize the urgent need for alternative antibacterial strategies. We engineered Escherichia coli to conjugatively transfer plasmids to specific E. coli and Pseudomonas aeruginosa recipient cells through the surface display of cognate nanobody/antigen (Nb/Ag) pairs. We further engineered mobilizable plasmids to carry CRISPR/Cas9 systems (pCrispr) for the selective killing of recipient cells harboring CRISPR/Cas9 target sequences. In the assembled programmed delivery system (PDS), Nb-displaying E. coli donors with different conjugation systems and mobilizable pCrispr plasmids suppressed the growth of Ag-displaying recipient cells to significantly greater extents than unpaired recipients. We also showed that anucleate minicells armed with conjugation machines and pCrispr plasmids were highly effective in killing E. coli recipients. Together, our findings suggest that bacteria or minicells armed with PDSs may prove highly effective as an adjunct or alternative to antibiotics for antimicrobial intervention.

Isolation of a bacteriophage targeting Pseudomonas aeruginosa and exhibits a promising in vivo efficacy

Pseudomonas aeruginosa is an important pathogen that causes serious infections. Bacterial biofilms are highly resistant and render bacterial treatment very difficult, therefore necessitates alternative antibacterial strategies. Phage therapy has been recently regarded as a potential therapeutic option for treatment of bacterial infections. In the current study, a novel podovirus vB_PaeP_PS28 has been isolated from sewage with higher lytic activity against P. aeruginosa. Isolated phage exhibits a short latent period, large burst size and higher stability over a wide range of temperatures and pH. The genome of vB_PaeP_PS28 consists of 72,283 bp circular double-stranded DNA, with G + C content of 54.75%. The phage genome contains 94 open reading frames (ORFs); 32 for known functional proteins and 62 for hypothetical proteins and no tRNA genes. The phage vB_PaeP_PS28 effectively inhibited the growth of P. aeruginosa planktonic cells and displayed a higher biofilm degrading capability. Moreover, therapeutic efficacy of isolated phage was evaluated in vivo using mice infection model. Interestingly, survival of mice infected with P. aeruginosa was significantly enhanced upon treatment with vB_PaeP_PS28. Furthermore, the bacterial load in liver and kidney isolated from mice infected with P. aeruginosa and treated with phage markedly decreased as compared with phage-untreated P. aeruginosa-infected mice. These findings support the efficacy of isolated phage vB_PaeP_PS28 in reducing P. aeruginosa colonization and pathogenesis in host. Importantly, the isolated phage vB_PaeP_PS28 could be applied alone or as combination therapy with other lytic phages as phage cocktail therapy or with antibiotics to limit infections caused by P. aeruginosa.

Quaternized chitosan coated copper sulfide nanozyme with peroxidase-like activity for synergistic antibacteria and promoting infected wound healing

Bacterial infection can hinder the infected wound healing process. Because of the growing drug-resistance bacteria, there is an urgent desire to develop alternative antibacterial strategies to the antibiotics. Herein, the quaternized chitosan coated CuS (CuS-QCS) nanozyme with peroxidase (POD)-like activity was developed through a facile biomineralized approach for synergistic efficient antibacterial therapy and wound healing. The CuS-QCS killed bacteria by the electrostatic bonding of positive charged QCS with bacteria and releasing Cu2+ to damage bacterial membrane. And importantly, CuS-QCS nanozyme exhibited higher intrinsic POD-like activity, which converted H2O2 with low concentration into highly toxic hydroxyl radical (OH) for the elimination of bacteria by oxidative stress. Through cooperation of POD-like activity, Cu2+ and QCS, CuS-QCS nanozyme exhibited excellent antibacterial efficacy of approximate 99.9 % against E. coli and S. aureus in vitro. In addition, the QCS-CuS was successfully used to promote the healing of S. aureus infected wound with good biocompatibility. This synergistic nanoplatform presented here shows great potential applications in the field of wound infection management.

Fighting bacterial pathogens with carbon nanotubes: focused review of recent progress.

The fast and global spread of bacterial resistance to currently available antibiotics results in a great and urgent need for alternative antibacterial agents and therapeutic strategies. Recent studies on the application of nanomaterials as antimicrobial agents have demonstrated their potential for the management of infectious diseases. Among the diverse palette of nanomaterials currently used in biomedical applications, carbon nanotubes (CNTs) have gained massive interest given their many valuable properties, such as high thermal and electrical conductivity, tensile strength, flexibility convenient aspect ratio, and low fabrication costs. All these features are augmented by facile conjugation with functional groups. CNTs are currently available in many configurations, with two main categories being single-walled and multi-walled CNTs, depending on the number of rolled-up single-layer carbon atoms sheets making up the nanostructure. Both classes have been identified over the past years as promising antibacterial agents but the current level of understanding of their efficiency still harbors many pending questions. This mini-review surveys recent progress on the topic of antibacterial effects of CNTs and examines the proposed mechanisms of action(s) of different CNT typologies, placing the main focus on past studies addressing the antibacterial activity on Staphylococcus aureus and Escherichia coli, two prototypical Gram-positive and Gram-negative pathogens, respectively.

Bioinspired MoS2 Nanosheet-Modified Carbon Fibers for Synergetic Bacterial Elimination and Wound Disinfection.

Bacterial infection is one of the most frequent wound complications and has become a major public health concern. Increasing resistance to antibiotics has been noted with these agents broadly used in wound management. It is an urgent demand to develop alternative antibacterial strategies with a reduced chance of resistance. Herein, a Nepenthes-mimicking nanosheet array of MoS2 on carbon fibers (CF-MoS2 ) is proposed to achieve dual bactericidal activities. First, the sharp edges of synthesized surfaces are capable of inducing physical disruption of cell membranes, demonstrating mechanical antibacterial activity like their natural counterparts. Second, in the presence of near-infrared light, bioinspired CF-MoS2 nanosheets are able to cause the death of damaged bacteria owing to their inherent photothermal properties. Such dual-functional modes endow the surfaces with nearly 100% killing efficiency for highly concentrated Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Furthermore, their potential to be applied as wound dressings for photothermal treatment of infectious wounds is also investigated in vivo. Bioinspired CF-MoS2 dressings show advantages of synergistic disinfection and efficient promotion of wound regeneration. It is foreseen that this high-performance and multifunctional CF-MoS2 could afford a feasible broad-spectrum treatment for non-antibiotic disinfection.

Antibacterial Pathways in Transition Metal-Based Nanocomposites: A Mechanistic Overview.

Across the planet, outbreaks of bacterial illnesses pose major health risks and raise concerns. Photodynamic,photothermal, and metal ion releaseeffects of transition metal-based nanocomposites (TMNs)were recently shown to be highly effective in reducing bacterial resistance and upsurges in outbreaks. Surface plasmonic resonance, photonics, crystal structures, and optical properties of TMNshave been used to regulate metal ion release, produce oxidative stress, and generate heat for bactericidal applications.The superior properties of TMNsprovide a chance to investigate and improve their antimicrobial actions, perhaps leading to therapeutic interventions. In this review, we discuss three alternative antibacterial strategies based on TMNs of photodynamic therapy,photothermal therapy, and metal ion release and their mechanistic actions. The scientific community has made significant efforts to address the safety, effectiveness, toxicity, and biocompatibility of these metallic nanostructures; significant achievements and trends have been highlighted in this review. The combination of therapies together has borne significant results to counter antimicrobial resistance (4-log reduction). These three antimicrobial pathways are separated into subcategories based on recent successes, highlighting potential needs and challenges in medical, environmental, and allied industries.

Antimicrobial Applications of Green Synthesized Bimetallic Nanoparticles from Ocimum basilicum.

Antibiotic resistance is an important and emerging alarm for public health that requires development of new potential antibacterial strategies. In recent years, nanoscale materials have emerged as an alternative way to fight pathogens. Many researchers have shown great interest in nanoparticles (NPs) using noble metals, such as silver, gold, and platinum, even though numerous nanomaterials have shown toxicity. To overcome the problem of toxicity, nanotechnology merged with green chemistry to synthesize nature-friendly nanoparticles from plants. Here, we describe the synthesis of NPs using silver (AgNPs) and platinum (PtNPs) alone or in combination (AgPtNPs) in the presence of Ocimum basilicum (O. basilicum) leaf extract. O. basilicum is a well-known medicinal plant with antibacterial compounds. A preliminary chemical-physical characterization of the extract was conducted. The size, shape and elemental analysis were carried out using UV-Visible spectroscopy, dynamic light scattering (DLS), and zeta potential. Transmission electron microscopy (TEM) confirmed polydisperse NPs with spherical shape. The size of the particles was approximately 59 nm, confirmed by DLS analysis, and the polydisperse index was 0.159. Fourier transform infrared (FTIR) demonstrated an effective and selective capping of the phytoconstituents on the NPs. The cytotoxic activities of AgNPs, PtNPs and AgPtNPs were assessed on different epithelial cell models, using the 3-[4.5-dimethylthiazol-2-yl]-2.5-diphenyltetrazolium bromide (MTT) cell proliferation assay, and discovered low toxicity, with a cell viability of 80%. The antibacterial potential of the NPs was evaluated against Escherichia coli (E. coli), Enterococcus faecalis (E. faecalis), Klebsiella pneumonia (K. pneumoniae), and Staphylococcus aureus (S. aureus) strains. Minimum inhibitory concentration (MIC) assays showed AgPtNP activity till the least concentration of NPs (3.15-1.56 µg/mL) against ATCC, MS, and MDR E. coli, E. faecalis, and S. aureus and the Kirby-Bauer method showed that AgPtNPs gave a zone of inhibition for Gram-positive and Gram-negative bacteria in a range of 9-25 mm. In addition, we obtained AgPtNP synergistic activity in combination with vancomycin or ampicillin antibiotics. Taken together, these results indicate that bimetallic nanoparticles, synthesized from O. basilicum leaf extract, could represent a natural, ecofriendly, cheap, and safe method to produce alternative antibacterial strategies with low cytotoxicity.

Metabolic Labeling Strategy Boosted Antibacterial Efficiency for Photothermal and Photodynamic Synergistic Bacteria-Infected Wound Therapy.

Pathogenic bacteria infections bring about a substantial risk to human health. Given the development of antibiotic-resistance bacteria, alternative antibacterial strategies with great inactivation efficiency and bacteria-binding ability are extremely attractive. In this work, a metabolic labeling photosensitizer, prepared by the coupling of commercial IR820 and d-propargylglycine (a type of d-amino acid, DAA) via a straightforward one-step incubation (IR820-DAA), could metabolically be incorporated into the bacterial wall via enzymatic reactions, thus enhancing antibacterial efficiency. The laser energy at 808 nm could make IR820-DAA a synergistic photothermal/photodynamic agent for efficient antibacterial therapy and wound healing. Furthermore, IR820-DAA exhibits good water solubility and biological safety for clinical translation and even possesses biofilm degradation activity toward methicillin-resistant Staphylococcus aureus (MRSA). Overall, the proposed IR820-DAA holds great promise as a nonantibiotic tool for the treatment of bacteria-related diseases and offers a blueprint for building the precise synergistic antibacterial therapeutic platform.

Safe-by-Design Antibacterial Peroxide-Substituted Biomimetic Apatites: Proof of Concept in Tropical Dentistry.

Bone infections are a key health challenge with dramatic consequences for affected patients. In dentistry, periodontitis is a medically compromised condition for efficient dental care and bone grafting, the success of which depends on whether the surgical site is infected or not. Present treatments involve antibiotics associated with massive bacterial resistance effects, urging for the development of alternative antibacterial strategies. In this work, we established a safe-by-design bone substitute approach by combining bone-like apatite to peroxide ions close to natural in vivo oxygenated species aimed at fighting pathogens. In parallel, bone-like apatites doped with Ag+ or co-doped Ag+/peroxide were also prepared for comparative purposes. The compounds were thoroughly characterized by chemical titrations, FTIR, XRD, SEM, and EDX analyses. All doped apatites demonstrated significant antibacterial properties toward four major pathogenic bacteria involved in periodontitis and bone infection, namely Porphyromonas gingivalis (P. gingivalis), Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans), Fusobacterium nucleatum (F. nucleatum), and S. aureus. By way of complementary tests to assess protein adsorption, osteoblast cell adhesion, viability and IC50 values, the samples were also shown to be highly biocompatible. In particular, peroxidated apatite was the safest material tested, with the lowest IC50 value toward osteoblast cells. We then demonstrated the possibility to associate such doped apatites with two biocompatible polymers, namely gelatin and poly(lactic-co-glycolic) acid PLGA, to prepare, respectively, composite 2D membranes and 3D scaffolds. The spatial distribution of the apatite particles and polymers was scrutinized by SEM and µCT analyses, and their relevance to the field of bone regeneration was underlined. Such bio-inspired antibacterial apatite compounds, whether pure or associated with (bio)polymers are thus promising candidates in dentistry and orthopedics while providing an alternative to antibiotherapy.

In Silico Screening of Natural Metabolites as Inhibitors of Biosynthesis and Transport of Enterobactin

As antibiotic resistance is becoming a more serious issue, eliminating essential nutrients from the microenvironment of pathogens, thereby diminishing their growth, would be an effective alternative to widely used antibiotics. Inhibition of iron sequestration in bacteria is one of the alternative antibacterial strategies. As bacteria use siderophores, small molecules that chelate iron from host proteins for iron sequestration, inhibition of siderophore biosynthesis and transport would be a promising way of finding an alternative to the antibiotics. The objective of the current work was to screen for natural metabolites as potential binders of selected drug targets involved in iron acquisition in E. coli. Isochorismate synthase (ICS), an enzyme involved in siderophore biosynthesis, enterobactin, and a membrane protein FepA transports enterobactin-Fe complex into bacterial cells, were chosen as drug targets. Forty-three marine metabolites and 87 plant metabolites were screened in silico, as inhibitors for the selected drug targets. Three marine metabolites viz. Plakorstatin B (-8.76) laurenditerpenol (-8.44), isogranulatimide (-8.39) and, and two plant metabolites: quercetin (-7.97) from Withania somnifera and vomifoliol (-7.96) from Morinda citrifolia were the top-binders for ICS, and further analysis indicated that these compounds interact with the same amino acids that are interacting with the natural ligand of ICS. Withanolide D (-12.61) from W. somnifera, rubiadin (-12.25), and daucosterol (-11.87) from M. citrifolia, and two marine metabolites: bistramide A (-11.8) and isogeoditin A (-11.56) were found to be the top-binders for FepA. These compounds could act as lead molecules for the design and development of effective siderophore inhibitors, thereby controlling the growth of microbial pathogens.

Copper Induces Protein Aggregation, a Toxic Process Compensated by Molecular Chaperones.

ABSTRACTCopper is well known for its antimicrobial and antiviral properties. Under aerobic conditions, copper toxicity relies in part on the production of reactive oxygen species (ROS), especially in the periplasmic compartment. However, copper is significantly more toxic under anaerobic conditions, in which ROS cannot be produced. This toxicity has been proposed to arise from the inactivation of proteins through mismetallations. Here, using the bacterium Escherichia coli, we discovered that copper treatment under anaerobic conditions leads to a significant increase in protein aggregation. In vitro experiments using E. coli lysates and tightly controlled redox conditions confirmed that treatment with Cu+ under anaerobic conditions leads to severe ROS-independent protein aggregation. Proteomic analysis of aggregated proteins revealed an enrichment of cysteine- and histidine-containing proteins in the Cu+-treated samples, suggesting that nonspecific interactions of Cu+ with these residues are likely responsible for the observed protein aggregation. In addition, E. coli strains lacking the cytosolic chaperone DnaK or trigger factor are highly sensitive to copper stress. These results reveal that bacteria rely on these chaperone systems to protect themselves against Cu-mediated protein aggregation and further support our finding that Cu toxicity is related to Cu-induced protein aggregation. Overall, our work provides new insights into the mechanism of Cu toxicity and the defense mechanisms that bacteria employ to survive.