Strong Antimicrobial Activity Research Articles

Transcriptomic and Biochemical Analysis of the Antimicrobial Mechanism of Lipopeptide Iturin W against Staphylococcus aureus

Staphylococcus aureus is one of the most serious pathogens threatening food safety and public health. We have previously showed that iturin W exhibited obvious antifungal activity on plant pathogens. In the present study, we found iturin W, especially C14 iturin W, showed strong antimicrobial activity against S. aureus, and the antimicrobial mechanism of C14 iturin W was further investigated by transcriptomic analysis and a related biochemical experiment. The results showed that C14 iturin W can reduce the expression levels of genes associated with the reactive oxygen species (ROS) scavenging enzyme and genes involved in arginine biosynthesis, thus leading to the increase in ROS levels of S. aureus. Furthermore, C14 iturin W can also interfere with proton dynamics, which is crucial for cells to regulate various biological possesses. Therefore, ROS accumulation and change in proton motive force are import ways for C14 iturin W to exert the antimicrobial activity. In addition, C14 iturin W can also reduce the expression levels of genes related to virulence factors and decrease the production of enterotoxins and hemolysins in S. aureus, indicating that C14 iturin W has a good potential in food and pharmaceutical fields to reduce the harm caused by S. aureus in the future.

Structural, morphological, optical, and antimicrobial study of Mikania micrantha (leaf) extract treated zinc doped cobalt ferrite nanoparticles and antibacterial clothing applications

To manage pathogenic diseases, different applications of nanotechnology have been harnessed to improve the antimicrobial and self-cleaning attributes of materials. The objective of this study is to examine the anti-microbial activity of silk thread; coated (ultra-sonication method) with Zn doped cobalt ferrite nanoparticles with future prospects of developing interlayer of surgical facemask or producing antibacterial wearing. The nanoparticles were synthesized following the co-precipitation method by using Mikania micrantha leaf extract. The potential antibacterial activity (against E. coli and S. aureus) of the thread as well as the nanoparticles was recorded using the Zone of Inhibition (ZOI) test result. XRD results showed the cubic crystal structure and the lattice parameter change due to Zn doping. SEM findings revealed particle agglomeration, though the particles retained an approximately spherical shape of around 52.498 nm for undoped and 32.13 nm for doped materials. FT-IR analysis confirmed that flavonoids from the leaf extract stabilized the nanoparticles. This research investigated the antibacterial capabilities of threads coated with nanoparticles; using the agar well diffusion method, the study established the robust antibacterial capabilities of the nanoparticles-coated thread. Notably, the CoFe2O4 NPs exhibited strong antimicrobial activity against specific bacterial strains, and Zn doping enhances this characteristic.

Epibiotic Bacteria Isolated from the Non-Indigenous Species Codium fragile ssp. fragile: Identification, Characterization, and Biotechnological Potential

Due to their richness in organic substances and nutrients, seaweed (macroalgae) harbor a large number of epiphytic bacteria on their surfaces. These bacteria interact with their host in multiple complex ways, in particular, by producing chemical compounds. The released metabolites may have biological properties beneficial for applications in both industry and medicine. In this study, we assess the diversity of culturable bacterial community of the invasive alga Codium fragile ssp. fragile with the aim to identify key groups within this epiphytic community. Seaweed samples were collected from the Northern Tunisian coast. A total of fifty bacteria were isolated in pure culture. These bacterial strains were identified by amplification of the ribosomal intergenic transcribed spacer between the 16S and the 23S rRNA genes (ITS-PCR) and by 16S rRNA sequencing. Antimicrobial activity, biochemical, and antibiotic resistance profile characterization were determined for the isolates. Isolated strains were tested for their antimicrobial potential against human and fish bacterial pathogens and the yeast Candida albicans, using the in vitro drop method. About 37% of isolated strains possess antibacterial activity with a variable antimicrobial spectrum. Ba1 (closely related to Pseudoalteromonas spiralis), Ba12 (closely related to Enterococcus faecium), and Bw4 (closely related to Pseudoalteromonas sp.) exhibited strong antimicrobial activity against E. coli. The isolated strain Ba4, closely related to Serratia marcescens, demonstrated the most potent activity against pathogens. The susceptibility of these strains to 12 commonly used antibiotics was investigated. Majority of the isolates were resistant to oxacillin, cefoxitin, tobramycin, and nitrofurantoin. Ba7 and Ba10, closely related to the Vibrio anguillarum strains, had the highest multidrug resistance profiles. The enzymes most commonly produced by the isolated strains were amylase, lecithinase, and agarase. Moreover, nine isolates produced disintegration zones around their colonies on agar plates with agarolitic index, ranging from 0.60 to 2.38. This investigation highlighted that Codium fragile ssp. fragile possesses an important diversity of epiphytic bacteria on its surface that could be cultivated in high biomass and may be considered for biotechnological application and as sources of antimicrobial drugs.

Understanding the biosynthesis, metabolic regulation, and anti-phytopathogen activity of 3,7-dihydroxytropolone in Pseudomonas spp.

The genus Pseudomonas is a prolific source of specialized metabolites with significant biological activities, including siderophores, antibiotics, and plant hormones. These molecules play pivotal roles in environmental interactions, influencing pathogenicity, inhibiting microorganisms, responding to nutrient limitation and abiotic challenges, and regulating plant growth. These properties mean that pseudomonads are suitable candidates as biological control agents against plant pathogens. Multiple transposon-based screens have identified a Pseudomonas biosynthetic gene cluster (BGC) associated with potent antibacterial and antifungal activities, which produces 7-hydroxytropolone (7-HT). In this study, we show that this BGC also makes 3,7-dihydroxytropolone (3,7-dHT), which has strong antimicrobial activity toward Streptomyces scabies, a potato pathogen. Through metabolomics and reporter assays, we unveil the involvement of cluster-situated genes in generating phenylacetyl-coenzyme A, a key precursor for tropolone biosynthesis via the phenylacetic acid catabolon. The clustering of these phenylacetic acid genes within tropolone BGCs is unusual in other Gram-negative bacteria. Our findings support the interception of phenylacetic acid catabolism via an enoyl-CoA dehydratase encoded in the BGC, as well as highlighting an essential role for a conserved thioesterase in biosynthesis. Biochemical assays were used to show that this thioesterase functions after a dehydrogenation-epoxidation step catalyzed by a flavoprotein. We use this information to identify diverse uncharacterized BGCs that encode proteins with homology to flavoproteins and thioesterases involved in tropolone biosynthesis. This study provides insights into tropolone biosynthesis in Pseudomonas, laying the foundation for further investigations into the ecological role of tropolone production.IMPORTANCEPseudomonas bacteria produce various potent chemicals that influence interactions in nature, such as metal-binding molecules, antibiotics, or plant hormones. This ability to synthesize bioactive molecules means that Pseudomonas bacteria may be useful as biological control agents to protect plants from agricultural pathogens, as well as a source of antibiotic candidates. We have identified a plant-associated Pseudomonas strain that can produce 3,7-dihydroxytropolone, which has broad biological activity and can inhibit the growth of Streptomyces scabies, a bacterium that causes potato scab. Following the identification of this molecule, we used a combination of genetic, chemical, and biochemical experiments to identify key steps in the production of tropolones in Pseudomonas species. Understanding this biosynthetic process led to the discovery of an array of diverse pathways that we predict will produce new tropolone-like molecules. This work should also help us shed light on the natural function of antibiotics in nature.

Synergistic antimicrobial activities of aqueous extract derived from olive byproduct and their modes of action

BackgroundPlant-derived antimicrobials (PDAs) are considered a viable alternative to synthetic antimicrobial agents. Diverse antimicrobial mechanisms of PDAs significantly reduce the risk of developing antimicrobial resistance. Utilization of PDAs also offers economic and environmental advantages, as they can be derived from agricultural byproducts, such as olive pomace.ResultsIn this study, a green, water-based, ultrasound-assisted extraction (UAE) was deployed to obtain aqueous olive pomace extract (OPE) from dry olive pomace. Total phenolic content, extraction yield, chemical compositions, and antimicrobial activities of OPE were evaluated. In addition, the potential synergistic interaction between the phenolic components in OPE and the antimicrobial mechanisms underlying the synergistic interaction were characterized. The results show that ca. 25 mg GAE/g of extraction yields were achieved by the UAE of dry olive pomace. Based on the high-performance liquid chromatography (HPLC) analysis, diverse phenolic compounds such as gallic acid (GA), hydroxytyrosol (HT), and 4-hydroxyphenylacetic acid (4-HPA) were identified in OPE. OPE exhibited strong antimicrobial activities, and 0.2 mg GAE/mL of OPE achieved > 5 log reductions of Escherichia coli O157:H7 and Listeria innocua cells within 30 min of treatment. A 3D isobologram analysis demonstrated that OPE exhibited strong synergistic antimicrobial activities, compared to those of individual phenolic components (GA, HT, or 4-HPA), showing interaction index (γ) of 0.092 and 0.014 against E. coli O157:H7 and L. innocua, respectively (γ < 1: synergistic activity). Antimicrobial mechanism analyses revealed that phenolic components in OPE exerted strong synergistic activities through diverse modes of action, and increased levels of oxidative stress, membrane damage, and decreased levels of metabolic activities were observed in the OPE-treated bacterial cells.ConclusionsThese findings demonstrate an approach for valorizing agricultural byproducts to develop plant byproduct-based antimicrobials with strong synergistic activities. Multiple modes of action of this byproduct extract may enable the control of diverse microbes in food and agriculture systems.Graphical abstract

Fish Gelatin-Based Flexible and Self-Healing Hydrogel Modified by Fe2(SO4)3

The application of fish gelatin (FG) is limited due to its poor mechanical properties and thermal stability, both of which could be significantly improved by gellan gum (GG) found in previous research. However, the FG/GG composite hydrogel was brittle and easily damaged by external forces. It was found that the composite hydrogel with Fe2(SO4)3 showed good flexibility and self-healing properties in the pre-experiment. Thus, the synergistic effect of FG, GG and Fe2(SO4)3 on the mechanical properties of the composite hydrogel was investigated in this study. According to one-way experiments, response surface tests and Texture Profile Analysis, it was found that under the optimum condition of FG concentration 186.443 g/L, GG concentration 8.666 g/L and Fe2(SO4)3 concentration 56.503 g/L, the springiness of the composite cylindrical hydrogel with the height of 25 mm formed in 25 mL beakers (bottom diameter 30 mm) was 7.602 mm. Determination of the rheological properties, compression performance, adhesive performance and self-healing properties showed that the composite hydrogel had good thermal stability, flexibility and self-healing properties with good adhesion, skin compliance and compressive strength, and it was easy to remove. The composite hydrogel showed strong antimicrobial activity against A. salmonicida and V. parahaemolyticus. All hydrogels showed a uniform and porous structure. The 3D structure of the composite hydrogel was much looser and more porous than the pure FG hydrogel. The flexible and self-healing composite hydrogel with some antimicrobial activity is suitable for the development of medical dressings, which broadens the applications of the composite hydrogel.

Improved Functions of Fermented Coffee by Lactic Acid Bacteria

Coffee is one of the most popular beverages in the world, and at present, specialty coffees are developing for better tastes, flavors, or functions. Fermented coffees also reflect this trend and some brands are commercialized. Unlike general fermented coffees, we tried to ferment coffee extract with several lactic acid bacteria. Finally, we selected three strains that persisted in the coffee extract, and show strong antimicrobial activity, for the fermentation starters. The strains were identified as Pediococcus pentosaceus (KNUT 0384), Lacticaseibacillus paracasei (CJNU 1840), and Lactiplantibacillus plantarum (CJNU 0441) based on 16S rRNA gene sequences. During the fermentation process, the total acidities (p &lt; 0.05 vs. the control, non-fermented coffee extract) and cell masses increased, which indicates that the bacteria metabolized properly in the extract. Furthermore, the fermented coffee extracts showed increased antimicrobial activities against Listeria monocytogenes (p &lt; 0.05 vs. the control) and Streptococcus mutans (p &lt; 0.05 vs. the control), increased anti-oxidative activities (p &lt; 0.05 vs. the control, except for the KNUT 0384 sample), decreased caffeine content (p &lt; 0.05 vs. the control, except for the KNUT 0384 sample), and increased chlorogenic acid content (p &lt; 0.05 vs. the control). Taken together, the fermented coffee extracts with the selected lactic acid bacteria could be specialty coffees where several functions are improved when compared with a control coffee extract.

Combining Aloin with TIENAM ameliorates cecal ligation and puncture-induced sepsis in mice by attenuating inflammation and modulating abdominal cavity microbiota

Despite the high mortality rate, sepsis lacks specific and effective treatment options. Conventional antibiotics, such as TIENAM (TIE; imipenem and cilastatin sodium for injection), face challenges owing to the emergence of bacterial resistance, which reduces their effectiveness and causes adverse effects. Addressing resistance and judicious drug use is crucial. Our research revealed that aloin (Alo) significantly boosts survival rates and reduces inflammation and bacterial load in mice with sepsis, demonstrating strong antimicrobial activity. Using a synergistic Alo + TIE regimen in a cecal ligation and puncture (CLP)-induced sepsis model, we observed a remarkable increase in survival rates from 10 % to 75 % within 72 h compared with the CLP group alone. This combination therapy also modulated inflammatory markers interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α, mitigated tissue damage, regulated immune cells by lowering NK, activated CD8+ and CD4+ T cells while increasing peritoneal macrophages, and decreased the bacterial load in the peritoneal cavity. We noted a significant shift in the abdominal cavity microbiota composition post-treatment, with a decrease in harmful bacteria, such as Lachnospiraceae_NK4A136_group, Klebsiella, Bacillus, and Escherichia, and an increase in beneficial bacteria, such as Lactobacillus and Mucispirillum. Our study emphasizes the efficacy of combining Alo with TIE to combat sepsis, and paves the way for further investigations and potential clinical applications aiming to overcome the limitations of TIE and enhance the therapeutic prospects of Alo.

Antimicrobial Activity against Cronobacter of Plant Extracts and Essential Oils in a Matrix of Bacterial Cellulose.

Bacterial cellulose (BC) is a biodegradable polymer resembling paper after being dried. It finds a growing number of applications in many branches of industry and in medicine. In the present study, BC was produced after Gluconacetobacter hansenii ATCC 23769 strain culture and used as a matrix for plant extracts (tulsi, brahmi, lemon, blackberry, nettle root, and nettle leave) and essential oils (cinnamon, sage, clove, mint, thyme, lemongrass, rosemary, lemon, anise, tea tree, lime, grapefruit, and tangerine), and the antimicrobial properties of these biomaterials was determined. The growth-inhibiting effects of plant extracts and essential oils combined with BC were analyzed against five Cronobacter species isolated from food matrix and two reference strains from the ATCC (513229 and 29544). Additional analyses were conducted for BC water activity and for its capability to absorb biologically active plant compounds. The cellulose matrix with a 50% extract from brahmi was found to effectively inhibit the growth of the selected Cronobacter strains. The other plant water extracts did not show any antimicrobial activity against the tested strains. It was demonstrated that BC soaked with thyme essential oil was characterized with the strongest antimicrobial activity in comparison to the other tested EOs. These study results indicate the feasibility of deploying BC impregnated with natural plant components as an active and environmentally-friendly packaging material.

Electrophoretically deposited Asphaltum punjabianum (Shilajit) coatings on polyvinylalcohol/carboxymethylcellulose hydrogels

The present study aims to develop Asphaltum punjabianum (namely Shilajit) coated Polyvinyl alcohol (PVA)/Carboxymethyl cellulose (CMC) hydrogels and examine their structural, morphological, degradation, and biological properties. Hydrogels were produced at two different concentrations: 70:30 PVA/CMC and 90:10 PVA/CMC. Following that, Shilajit was applied to the synthesized hydrogels using electrophoretic deposition for a duration of 3 min at 30 V. The scanning electron microscopy images showed that the hydrogel's surface had a regular distribution of irregular Shilajit particles. Fourier transform infrared spectroscopy (FTIR) analysis demonstrated the presence of hydrogen bonding between PVA and CMC hydrogels and Shilajit, indicating the successful deposition of Shilajit on the hydrogel. The hydrogels coated with Shilajit exhibited strong antimicrobial activity, resulting in an inhibition zone measuring 34 mm against Escherichia coli (E. coli) and 41 mm against Staphylococcus aureus (S. aureus). The hydrogels exhibited a cell viability of 80 % with mesenchymal stem cells (MSCs), and the release of collagen II also increased. Furthermore, the PVA/CMC/Shilajit hydrogel exhibited a lower degradation rate compared to the PVA/CMC hydrogel. The results of the swelling, degradation, and drug release studies indicate that the shilajit coating is appropriate for the long-term process of tissue and cartilage regeneration.

Fe-doped herbal medicine-based carbon dots nanozyme as safe and effective antimicrobial and wound healing agent

Bacterial infections pose a serious worldwide public health concern and play an important role in slowing or dramatically delaying wound healing. However, traditional antibiotics are faced with obstacles such as bacterial resistance and unsatisfactory biocompatibility, which has impeded further clinical translation. In recent years, antimicrobial nanomaterials have emerged as viable alternatives for combating bacterial infections, and carbon dots (CDs) have received particularly widespread attention due to their superior characteristics. In this work, a simple and eco-friendly one-step hydrothermal method was employed using the natural herbal medicine Eucommia ulmoides as a biomass carbon source to synthesize an Fe-doped CDs nanozyme (Fe-CDs) with good peroxidase-like (POD-like) activity, high biocompatibility, and strong antimicrobial activity for safe and effective antimicrobial therapy and the promotion of wound healing. L929 cells co-cultured with Fe-CDs did not show significant cytotoxicity and favored cell proliferation at appropriate concentrations. In addition, Fe-CDs catalyzed the decomposition of low-concentration H2O2 to ·OH, leading to enhanced antimicrobial activity. Both in vitro and in vivo experiments demonstrated that Fe-CDs exhibit potent antibacterial properties, the ability to promote cell migration and angiogenesis, and significant potential for promoting the healing of infected wounds. In summary, a green and safe antimicrobial nanozyme based on a biomass herbal medicine was developed in this work, offering promising insight into the development of novel antimicrobial materials and tissue regeneration engineering.

Research Note: Curbing Salmonella Enteritidis in broiler chickens with palm-free medium-chain fatty acids

Salmonellosis is still one of the most reported zoonoses worldwide and poultry meat is a major source, as chickens are often persistent carriers of Salmonella. Medium-chain fatty acids (MCFA) are known for their strong antimicrobial activity. MCFAs used today in the animal feed industry, however, mainly originate from the palm oil industry, which is notorious for its negative impact on the climate. We investigated the effect of a specific blend of palm-free MCFAs (ranging from C6 to C9) on Salmonella Enteritidis (SE) colonization in broiler chickens and in vitro SE characteristics. Fifty Ross 308 broiler chickens were randomly divided in 2 treatment groups. Chickens received either un-supplemented feed or feed supplemented with 300 ppm MCFAs from D0 onwards. On D7, all chickens were orally inoculated with 1600 CFU of SE. Cloacal swabs (D11) and samples of liver and caeca (D12) of all animals were collected and SE was enumerated. Percentage of SE-positive caecum samples was significantly (P = 0.044) reduced in birds receiving MCFAs compared to those receiving unsupplemented feed (36% vs. 64%). In vitro work performed with the same SE strain showed that preincubating the Salmonella bacteria with MCFAs at a sub-minimal inhibitory concentration significantly (p < 0.05) reduced bacterial adhesion to and invasion in Caco-2 cells, which may explain the observed reduction in intestinal SE colonization in the in vivo trial. Together, these results show that the tested eco-friendly MCFA blend could be a promising tool in the control of Salmonella in broilers.

Unravelling the secondary metabolome and biocontrol potential of the recently described species Bacillus nakamurai

In the prospect of use of natural products as safe and eco-friendly alternatives to chemical pesticides, the Bacillus nakamurai BDI-IS1 strain, derived from a Burundian soil sample, was selected among other bacterial isolates for its in vitro strong antimicrobial activities against a range of bacterial and fungal phytopathogens. Genome mining coupled with metabolomics revealed that it produces bioactive secondary metabolites including surfactins, iturins A, bacillaenes, bacillibactin, bacilysin, plantazolicin, and potentially amylocyclicin, bacinapeptin and LCI. The antagonistic activity of some of these metabolites was demonstrated by testing mutant strains of BDI-IS1. Although this bacterium is not able to produce the large arsenal of secondary metabolites as the commercial strain Bacillus velezensis QST713, greenhouse experiments show that BDI-IS1 is able to protect tomato and maize plants against early blight and northern leaf blight caused by Alternaria solani and Exserohilum turcicum, respectively, at levels similar to or better than QST713. The reduction of these foliar diseases, following root or leaf application of the bacterial suspension demonstrates that BDI-IS1 can act by direct antibiosis and by inducing plant defence mechanisms. These findings indicate that B. nakamurai BDI-IS1 can be considered as a good candidate for biocontrol of plant diseases prevailing in tropical regions, and encourage further research into its spectrum of activity, its requirements and the conditions needed to ensure its efficacy.

Oxygen and air cold plasma for the inactivation of Bacillus cereus in low-water activity soy powder

Cold plasma (CP) technology is a promising alternative to thermal treatments for the microbial decontamination of foods with low-water activity. The aim of this work is study the application of low-pressure CP (0.35 mbar) for the inactivation of Bacillus cereus in a soybean powder matrix using O₂ and synthetic air as ionizing gases. The parameters tested were an input power of 100, 200 and 300 W and an exposure time of 10 to 30 min. The excited reactive species formed were monitored by optical emission spectroscopy, and survival data were analyzed using the Weibull mathematical model. Treatments with both gases were effective in inactivating B. cereus. Air plasma resulted in a maximum 3.71-log reduction in bacterial counts at 300 W and 30 min, while O2 plasma showed the strongest inactivation ability, achieving levels higher than 5 log cycles at 300 W and > 25 min. This is likely due to the strong antimicrobial activity of oxygen-derived radicals together with carbon monoxide as an oxidation by-product. In addition, the Weibull distribution function accurately modeled the inactivation of B. cereus. Cold plasma technology is a promising approach for the decontamination of bacteria in low-water activity foods.

Superabsorbent crosslinked carboxymethyl cellulose-PEG hydrogel containing a nutgall extract as a broad antimicrobial agent for wound dressing applications

The treatment of chronic wounds encounters major challenges from oxidative stress that results from chronic inflammation and microbial infections. A hydrogel containing an ethanolic extract of Quercus infectoria galls (Qi) was developed as a new therapeutic strategy for the treatment of chronically infected wounds. FTIR confirmed the presence of bioactive compounds with 9.42 mg/g gallic acid as revealed by HPLC. Qi hydrogel presented a rough and compact surface with macroporous networks that contributed to an extremely high absorption of wound exudate equivalent to approximately 2300 % of the weight of the hydrogel. The biological activities of Qi hydrogel were compared with those of commercially-available products. According to the kinetic release, the correlation coefficients showed that the hydrogel fitted to the Higuchi model. Qi hydrogel exhibited strong antimicrobial activity against pathogens of clinical importance associated with wound infections. Minimum inhibitory concentrations and minimum bactericidal/fungicidal concentrations ranged from 0.24 to 250 and 3.91 to >250 mg/mL, respectively. In addition, microbial biofilms were significantly inhibited compared with the untreated control (p < 0.05). At concentrations from 0.78 to 12.5 mg/mL, Qi hydrogel scavenged almost 100 % of DPPH and ABTS radicals and showed a ferric ion reducing power of 443.11 μM FeSO4/g hydrogel by FRAP assay. A biocompatibility assessment of the hydrogel on L929 fibroblast cells confirmed no toxic effects and the hydrogel significantly inhibited lipopolysaccharide-induced nitric oxide production in RAW 264.7 macrophages (p < 0.05). The absorbency, permeability, phytochemical compounds and biological activities of Qi hydrogel are suitable properties of a dressing for treating and preventing chronically infected wounds.

A bacteriocin expression platform for targeting pathogenic bacterial species

Bacteriocins are antimicrobial peptides that are naturally produced by many bacteria. They hold great potential in the fight against antibiotic resistant bacteria, including ESKAPE pathogens. Engineered live biotherapeutic products (eLBPs) that secrete bacteriocins can be created to deliver targeted bacteriocin production. Here we develop a modular bacteriocin secretion platform that can be used to express and secrete multiple bacteriocins from non-pathogenic Escherichia coli host strains. As a proof of concept we create Enterocin A (EntA) and Enterocin B (EntB) secreting strains that show strong antimicrobial activity against Enterococcus faecalis and Enterococcus faecium in vitro, and characterise this activity in both solid culture and liquid co-culture. We then develop a Lotka-Volterra model that can be used to capture the interactions of these competitor strains. We show that simultaneous exposure to EntA and EntB can delay Enterococcus growth. Our system has the potential to be used as an eLBP to secrete additional bacteriocins for the targeted killing of pathogenic bacteria.

Enhancing curcumin nanoparticle synthesis through wet-milling: Comparative analysis of physico-chemical and antimicrobial properties of nano-curcumin with micro-curcumin

Curcumin efficacy is limited due to its low water-solubility and absorption, making curcumin nanoparticles (CN) useful alternatives. This study aimed to optimize CN synthesis through wet-milling using Response Surface Methodology (RSM) – Box-Behnken Design (BBD), considering mean particle size, followed by a comparison between CN synthesized under optimum conditions with curcumin. CN presented the least particle size (35.9 ± 0.1 nm) with a polydispersity index (PDI) of 0.0621 ± 0.0093, radical scavenging ability (RSA) of 89.97% ± 0.57, solubility of 10.46 ± 0.03 μg/mL and dissolution rate of 97.9% ± 1.4 under optimum conditions (curcumin solution concentration of 3.73 mg/mL, flow rate of 0.16 mL/min and ultrasonication time of 38.24 min). However, curcumin showed an average particle size of 671.1 ± 0.9 nm, PDI of 0.2060 ± 0.0104, RSA of 78.11% ± 1.05, solubility of 0.96 ± 0.07 μg/mL and dissolution rate of 11.9% ± 1.7, while being more thermodynamically stable. Fourier Transform Infrared (FTIR) spectroscopy demonstrated that both curcumin and CN had an identical chemical structure. X-Ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC) showed lower crystallinity of CN, and microbiological analysis confirmed their stronger antimicrobial activity as compared with curcumin. Our findings revealed that optimizing the synthesis parameters of CN can improve the resulting nanoparticles’ characteristics, supporting their bioavailability and application as antimicrobial and antioxidant agents in food storage.

Mitochondrial N‐Terminal Signal Sequences as Novel Antimicrobial and Annticancer Peptides

AbstractN‐terminal mitochondrial targeting sequences (MTS) are signal peptides to drive the localization and import of mitochondrial protein and exhibit an amphipathic α‐helix structure similar to that of almost all antimicrobial peptides (AMPs). Here, 2,939 mitochondrial proteins are excavated from various organisms, and 574 MTS are selected with an MTS possibility score exceeding 0.5, as determined via MitoFates (http://mitf.cbrc.jp/MitoFates/cgi‐bin/top.cgi). 26 MTS composed of less than 20 amino acids is synthesized and analyzed their antimicrobial activities. The results showed that approximately 50% of MTS exhibited antimicrobial activity. Among them, human mitochondrial transcription termination factor 2 (hMTERF2‐ts) is identified as an AMP candidate with strong antimicrobial activity against gram‐positive and gram‐negative bacteria, antibiotics‐resistant (AR) bacteria, and fungi. Furthermore, it shows anticancer activities against various cancer cells, such as MDA‐MB‐231, HT‐29, HepG2, and Panc‐1 cells, with high stability against proteases, heat, pH, and salt, and low cytotoxicity toward normal cells, HaCaT and RAW 264.7. In addition, hMTERF2‐ts effectively prevented the growth of Panc‐1‐implanted tumors without weight loss in BALB/c nude mice. In conclusion, this study suggests that MTSs of protozoa are powerful and novel AMP candidates with low cytotoxicity against normal cells.

Determination of in vitro synergy and antibiofilm activities of antimicrobials and essential oil components

Using existing adrentimicrobials with essential oil components to prevent antimicrobial resistance is an alternative strategy. This study aimed to evaluate the resistance status, synergistic combinations, and in vitro biofilm formation activities of clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA), Stenotrophomonas maltophilia and Candida albicans against antimicrobial agents and cinnamaldehyde, carvacrol, eugenol, limonene and eucalyptol. Antimicrobial activities were evaluated by microdilution, cytotoxicity by XTT, synergy by checkerboard and time-kill, and biofilm inhibition by microplate methods. Cinnamaldehyde and carvacrol showed strong antimicrobial activity. Synergistic effects were observed when using all essential oils with antimicrobials. Only two C. albicans isolates showed antagonism with cinnamaldehyde and fluconazole. The constituents showed cytotoxic effects in the L929 cell line (except limonene). A time-kill analysis revealed a bacteriostatic effect on S. maltophilia and MRSA isolates and a fungicidal effect on C. albicans isolates. These results are important for further research to improve antimicrobial efficacy or to develop new agents.

Glycine-replaced epinecidin-1 variant bestows better stability and stronger antimicrobial activity against a range of nosocomial pathogenic bacteria.

Epinecidin-1 (epi-1), an antimicrobial peptide first identified in marine grouper fish, has multifunctional bioactivities. The present study aims to improve its therapeutic potential via structural modifications that could enhance its antimicrobial activity and stability. To achieve it, we replaced glycine and the first histidine in the parent epi-1 with lysine, which resulted in a peptide with a repeating KXXK motif and improved physiochemical properties related to antimicrobial activity. This modified peptide, referred to as glycine-to-lysine replaced-epi-1, also gained stability and a twofold increase in helical propensity. To produce the active peptide, overlap extension PCR was employed to generate the gene of GK-epi-1 via site-directed mutagenesis, which was then cloned into the pET-32a vector and expressed as a recombinant fusion protein in Escherichia coli C43 (DE3) strain. The recombinant protein was purified and digested with enterokinase to release the active peptide fragment, which was then evaluated for antimicrobial activity and stability. The lysine substitution led to an enhancement in broad-spectrum antimicrobial activity against a wide range of nosocomial pathogenic bacteria.