Comparative Evaluation of the Antimicrobial Activity of Different Antimicrobial Peptides against a Range of Pathogenic Bacteria

Evaluation of the antimicrobial efficiency of three novel chimeric peptides through biochemical and biophysical analyses

Three chimeric membrane-active antimicrobial peptides (AMPs) were designed from previously characterized parental molecules, namely pandinin-2, ascaphin-8, and maximin-3. The aim of constructing these chimeras was to obtain sequences with improved therapeutic indices or increased activity, while simultaneously investigating the functional roles of key segments of the parental peptides. Chimera-1 was the most active peptide against clinically relevant bacterial species, followed by chimera-2, and chimera-3, respectively, with no clear preference towards Gram-negative or Gram-positive strains. Escherichia coli and Pseudomonas aeruginosa were the most sensitive bacteria, while Klebsiella pneumoniae and Staphylococcus aureus were resistant to AMP activity. All peptides presented significantly lower activities towards human erythrocytes, with chimera-1 being the most selective. Additionally, only chimera-2 showed cytotoxicity towards Vero cells. Calcein leakage and dynamic light scattering assays using liposomal formulations indicated that the chimeras conserved the pore forming membrane perturbation mechanisms of the parental molecules. Peptide interaction also reduced membrane fluidity. Circular dichroism (CD) data showed disordered peptides in aqueous solution that transitioned into alpha helical structures lipid bilayer environments. In silico assessments correlated well with microbiological and in vitro experimental data. All peptides established greater contact with the bacterial biomimetic membrane compared to the erythrocyte system, as analyzed by distance from membrane surface, number of contacts, solvent accessible surface area, and number of hydrogen bonds. Additionally, the presence of the bilayer lipid patches favored peptide folding, consistent with CD experiments. Molecular dynamics simulations of peptide aggregation revealed that chimera-2 formed the largest oligomers, consistent with the predicted aggregation propensities and the predicted physico-chemical properties. Interaction with membrane surfaces resulted in smaller clusters while low or lack of interaction favored larger aggregates. Overall, the chimeric peptides displayed higher activity and selectivity compared to the parental ones. The contribution of the flanking regions of pandidin-2 and maximin-3 with respect to the core region of ascaphin-8 was not clear.

Design of Natterins-based peptides improves antimicrobial and antiviral activities

The biochemical analysis of animal venoms has been intensifying over the years, enabling the prediction of new molecules derived from toxins, harnessing the therapeutic potential of these molecules. From the venom of the fish Thalassophryne nattereri, using in silico methods for predicting antimicrobial and cell-penetrating peptides, two peptides from Natterins with promising characteristics were synthesized and subjected to in vitro and in vivo analysis. The peptides were subjected to stability tests and antimicrobial assays, cytotoxicity in murine fibroblast cells, antiviral assays against the Chikungunya virus, and the toxicity on G. mellonella was also evaluated. The findings underscore the peptides' robust stability under varying temperatures and pH conditions and resistance to proteolytic degradation. The peptides demonstrated significant antimicrobial efficacy, minimal cytotoxicity, and low hemolytic activity. Although their antiviral efficacy was limited, they showed potential at specific stages of viral replication. The in vivo toxicity tests indicated a favorable safety profile. These findings suggest that this approach can aid in the development of antimicrobial agents, offering a faster and personalized method to combat microbial infections, and represent a promising discovery in venom biotechnology research.

Antibacterial and photocatalytic potential of piperine-derived zinc oxide nanoparticles against multi-drug-resistant non-typhoidal Salmonella spp

BACKGROUND

Drug-resistant pathogens and industrial dye wastes have emerged as critical global public health concerns, posing significant risks to human and animal health, as well as to environmental sustainability. Green synthesized nano absorbents were found to be a viable strategy for treating drug-resistant pathogens and in wastewater. Hence, this study endeavored the synthesis of piperine-driven nano-zinc oxide (ZnONPs) and evaluated them for antibacterial, antibiofilm, and photocatalytic disinfection potential against multi-drug resistant (MDR) foodborne strains of non-typhoidal Salmonella (NTS). Besides, the dye degradation potential of ZnONPs when exposed to UV, sunlight, and LED lights and their antioxidant capacity were assessed.

RESULTS

Initially, in silico analysis of piperine revealed drug-likeliness with minimal toxicity and strong interaction between piperine and OmpC motifs of Salmonella spp. UV spectroscopy of ZnONPs revealed a prominent absorption peak at 340 nm, while PXRD analysis confirmed the hexagonal wurtzite structure of ZnONPs by exhibiting peaks at 30°, 35.6°, 41.3°, 43.6°, 44.3°, 48°, 53°, 58°, and 59.2°, which corresponded to the lattice planes (102), (110), (103), (200), (112), (004), (104), (210), and (211). Additionally, the TEM images demonstrated predominantly spherical ZnONPs with hexagonal wurtzite crystalline SAED pattern. The minimum inhibitory concentration and minimum bactericidal concentration values (µg/mL) of the ZnONPs were found to be 62.50 and 125, respectively. The ZnONPs were observed to be safe with minimal hemolysis (less than 2%) in chicken RBCs, and no cytopathic effects were observed in the MTT assay using HEK cell lines. The NPs were found to be variably stable (high-end temperatures, proteases, cationic salts, and diverse pH), and were tested safe towards commensal gut lactobacilli. Additionally, in vitro time-kill kinetic assay indicated that the MDR-NTS strains were eliminated after co-incubating with ZnONPs for 6 h. The photocatalytic studies exhibited complete bacterial elimination under visible light at 4 h. Interestingly, the ZnONPs significantly inhibited the biofilm formation in the crystal violet staining assay by MDR-NTS strains (P < 0.001) at 24 and 48 h. Besides, a dose-dependent reducing power assay and 2,2'- azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•+) assay were exhibited. Moreover, ZnONPs significantly degraded methylene blue, crystal violet, and rhodamine-B under different light sources (sunlight, UV light, and LED).

CONCLUSIONS

This study revealed a sustainable one-pot method of synthesizing ZnONPs from piperine, which might be used as a viable antibacterial candidate with antioxidant, antibiofilm, and photocatalytic properties with eco-friendly implications and wastewater treatment.

Novel antimicrobial defensin peptides from different coleopteran insects (Coleoptera: Insecta): identification, characterisation and antimicrobial properties

Antimicrobial peptides are crucial components of the immune systems of both vertebrates and invertebrates. Here, defensins, the most studied class of antimicrobial molecules in arthropods were investigated in four coleopteran insect species: Harpalus rufipes (DeGeer, 1774), Mylabris quadripunctata (Linnaeus, 1767), Sphaeridium marginatum (Linnaeus, 1758), and Ocypus mus (Brullé, 1832). The peptides synthesized with over 95% purity and their antimicrobial activities were evaluated by MIC test method. As a result, it was determined that Mylabris quadripunctata defensin (MqDef) showed high antimicrobial activity against Staphylococcus aureus and MRSA, whereas Sphaeridium marginatum (SmDef) and Harpalus rufipes (HrDef) defensins against Candida tropicalis.

Proline-Rich Antimicrobial Peptides from Invertebrates

Antimicrobial peptides (AMPs) constitute a large and diverse group of molecules with antibacterial, antifungal, antiviral, antiprotozoan, and anticancer activity. In animals, they are key components of innate immunity involved in fighting against various pathogens. Proline-rich (Pr) AMPs are characterized by a high content of proline (and arginine) residues that can be organized into Pro-Arg-Pro motifs. Such peptides have been described in many invertebrates (annelids, crustaceans, insects, mollusks) and some vertebrates (mammals). The main objective of this review is to present the diversity of invertebrate PrAMPs, which are associated with the presence of cysteine-rich domains or whey acidic protein domains in the molecular structure, in addition to the presence of characteristic proline-rich regions. Moreover, PrAMPs can target intracellular structures in bacteria, e.g., 70S ribosomes and/or heat shock protein DnaK, leading to the inhibition of protein synthesis and accumulation of misfolded polypeptides in the cell. This unique mechanism of action makes it difficult for pathogens to acquire resistance to this type of molecule. Invertebrate PrAMPs have become the basis for the development of new synthetic analogues effective in combating pathogens. Due to their great diversity, new highly active molecules are still being searched for among PrAMPs from invertebrates.

Combined action of two synthetic ultrashort antimicrobial peptides exhibiting synergistic effects against clinically significant resistant bacteria

Background and Aim

The emergence and proliferation of multidrug-resistant bacteria pose a global health crisis. This issue arises from the overuse and misuse of antibiotics, coupled with the pharmaceutical industry's limited development of new drugs, which is constrained by financial disincentives and regulatory hurdles. This study aimed to investigate the combined antibacterial efficacy and safety profile of the combined ultrashort antimicrobial peptides (AMPs) WW-185 and WOW against antibiotic-resistant bacterial strains.

Materials and Methods

The WW-185 and WOW peptides were synthesized through solid-phase methods and purified using reverse-phase high-performance liquid chromatography, and their purity was confirmed by mass spectrometry. Antibacterial activity was evaluated using broth dilution and checkerboard assays to assess both individual and combined effects of the peptides against Staphylococcus aureus (including methicillin-resistant Staphylococcus aureus [MRSA]) and Escherichia coli (including extended-spectrum beta-lactamases [ESBL]-producing strains). The synergy between the peptides was quantified using fractional inhibitory concentration indices. Hemolytic activity was also assessed to determine cytotoxicity toward red blood cells.

Results

The combination of WW-185 and WOW exerted synergistic effects against both MRSA and ESBL-producing E. coli, with reduced minimal inhibitory concentrations compared with the individual treatments. The peptides exhibited minimal hemolytic activity, indicating low toxicity.

Conclusion

The combination of the ultrashort AMPs WW-185 and WOW shows promising synergistic antibacterial effects against resistant bacteria, with potential for further therapeutic development due to their enhanced efficacy and low toxicity.

Pneumococcal surface protein A (PspA) prevents killing of Streptococcus pneumoniae by indolicidin

Pneumococcal surface protein A (PspA) is an important virulence factor in Streptococcus pneumoniae that binds to lactoferrin and protects the bacterium from the bactericidal action of lactoferricins-cationic peptides released upon lactoferrin proteolysis. The present study investigated if PspA can prevent killing by another cationic peptide, indolicidin. PspA-negative pneumococci were more sensitive to indolicidin-induced killing than bacteria expressing PspA, suggesting that PspA prevents the bactericidal action of indolicidin. Similarly, chemical removal of choline-binding proteins increased sensitivity to indolicidin. The absence of capsule and PspA had an additive effect on pneumococcal killing by the AMP. Furthermore, anti-PspA antibodies enhanced the bactericidal effect of indolicidin on pneumococci, while addition of soluble PspA fragments competitively inhibited indolicidin action. Previous in silico analysis suggests a possible interaction between PspA and indolicidin. Thus, we hypothesize that PspA acts by sequestering indolicidin and preventing it from reaching the bacterial membrane. A specific interaction between PspA and indolicidin was demonstrated by mass spectrometry, confirming that PspA can actively bind to the AMP. These results reinforce the vaccine potential of PspA and suggest a possible mechanism of innate immune evasion employed by pneumococci, which involves binding to cationic peptides and hindering their ability to damage the bacterial membranes.

Chemokines Kill Bacteria by Binding Anionic Phospholipids without Triggering Antimicrobial Resistance

Classically, chemokines coordinate leukocyte trafficking during immune responses; however, many chemokines have also been reported to possess direct antibacterial activity in vitro. Yet, the bacterial killing mechanism of chemokines and the biochemical properties that define which members of the chemokine superfamily are antimicrobial remain poorly understood. Here we report that the antimicrobial activity of chemokines is defined by their ability to bind phosphatidylglycerol and cardiolipin, two anionic phospholipids commonly found in the bacterial plasma membrane. We show that only chemokines able to bind these two phospholipids kill Escherichia coli and Staphylococcus aureus and that they exert rapid bacteriostatic and bactericidal effects against E. coli with a higher potency than the antimicrobial peptide beta-defensin 3. Furthermore, our data support that bacterial membrane cardiolipin facilitates the antimicrobial action of chemokines. Both biochemical and genetic interference with the chemokine-cardiolipin interaction impaired microbial growth arrest, bacterial killing, and membrane disruption by chemokines. Moreover, unlike conventional antibiotics, E. coli failed to develop resistance when placed under increasing antimicrobial chemokine pressure in vitro. Thus, we have identified cardiolipin and phosphatidylglycerol as novel binding partners for chemokines responsible for chemokine antimicrobial action. Our results provide proof of principle for developing chemokines as novel antibiotics resistant to bacterial antimicrobial resistance mechanisms.

Ratanjot (Alkanna tinctoria L.) Root Extract, Rich in Antioxidants, Exhibits Strong Antimicrobial Activity against Foodborne Pathogens and Is a Potential Food Preservative

Natural and sustainable plant-based antioxidants and antimicrobials are highly desirable for improving food quality and safety. The present investigation assessed the antimicrobial and antioxidant properties of active components from Alkanna tinctoria L. (herb) roots, also known as Ratanjot root. Two methods were used to extract active components: microwave-assisted hot water (MAHW) and ethanolic extraction. MAHW extract yielded 6.29%, while the ethanol extract yielded 18.27%, suggesting superior Ratanjot root extract powder (RRP) solubility in ethanol over water. The ethanol extract showed significantly higher antioxidant activity than the MAHW extract. Gas Chromatography-Mass Spectrometry analysis revealed three major phenolic compounds: butanoic acid, 3-hydroxy-3-methyl-; arnebin 7, and diisooctyl pthalate. The color attributes (L*, a*, b*, H°ab, C*ab) for the ethanolic and MAHW extracts revealed significant differences (p < 0.05) in all the above parameters for both types of extracts, except for yellowness (b*) and chroma (C*ab) values. The ethanol extract exhibited antimicrobial activity against 14 foodborne bacteria, with a significantly higher inhibitory effect against Gram-positive bacteria (Listeria monocytogenes and Staphylococcus aureus) than the Gram-negative bacteria (Salmonella enterica serovar Typhimurium and Escherichia coli). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were both 25 mg/mL for the Gram-negative bacteria, while the MIC and MBC concentrations varied for Gram-positive bacteria (0.049-0.098 mg/mL and 0.098-0.195 mg/mL) and the antimicrobial effect was bactericidal. The antimicrobial activities of RRP extract remained stable under broad temperature (37-100 °C) and pH (2-6) conditions, as well as during refrigerated storage for 30 days. Application of RRP at 1% (10 mg/g) and 2.5% (25 mg/g) levels in a cooked chicken meatball model system prevented lipid oxidation and improved sensory attributes and retarded microbial growth during refrigerated (4 °C) storage for 20 days. Furthermore, the RRP extract was non-toxic when tested with sheep erythrocytes and did not inhibit the growth of probiotics, Lacticaseibacillus casei, and Lactiplantibacillus plantarum. In conclusion, the study suggests that RRP possesses excellent antimicrobial and antioxidant activities, thus making it suitable for food preservation.

Cellulose nanocrystals derived from chicory plant: an un-competitive inhibitor of aromatase in breast cancer cells via PI3K/AKT/mTOP signalling pathway

A significant contributing factor in the development of breast cancer is the estrogens. The synthesis of estrogens is primarily facilitated by aromatase (CYP19), a cytochrome P450 enzyme. Notably, aromatase is expressed at a higher level in human breast cancer tissue compared with the normal breast tissue. Therefore, inhibiting aromatase activity is a potential strategy in hormone receptor-positive breast cancer treatment. In this study, Cellulose Nanocrystals (CNCs) were obtained from Chicory plant waste through a sulfuric acid hydrolysis method with the objective of investigating that whether the obtained CNCs could act as an inhibitor of aromatase enzyme, and prevent the conversion of androgens to estrogens. Structural analysis of CNCs was carried out using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), while morphological results were obtained using AFM, TEM, and FE-SEM. Furthermore, the nano-particles were found to be spherical in shape with a diameter range of 35-37 nm and displayed a reasonable negative surface charge. Stable transfection of MCF-7 cells with CYP19 has demonstrated the ability of CNCs to inhibit aromatase activities and prevent cell growth by interfering with the enzyme activities. Spectroscopic results revealed the binding constant of CYP19-CNCs and (CYP19-Androstenedione)-CNCs complexes to be 2.07 × 103 L/gr and 2.06 × 104 L/gr, respectively. Conductometry and CD data reported different interaction behaviors among CYP19 and CYP19-Androstenedione complexes at the presence of CNCs in the system. Moreover, the addition of CNCs to the solution in a successive manner resulted in the enhancement of the secondary structure of the CYP19-androstenedione complex. Additionally, CNCs showed a marked reduction in the viability of cancer cells compared to normal cells by enhancing the expression of Bax and p53 at protein and mRNA levels, and by decreasing mRNA levels of PI3K, AKT, and mTOP, as well as protein levels of PI3Kg-P110 and P-mTOP, in MCF-7 cells after incubation with CNCs at IC50 concentration. These findings confirm the decrease in proliferation of breast cancer cells associated with induction of apoptosis through down-regulation of the PI3K/AKT/mTOP signaling pathway. According to the provided data, the obtained CNCs are capable of inhibiting aromatase enzyme activity, which has significant implications for the treatment of cancer.Communicated by Ramaswamy H. Sarma.

Antibacterial activity of a short de novo designed peptide against fish bacterial pathogens

In the face of increasing antimicrobial resistance in aquaculture, researchers are exploring novel substitutes to customary antibiotics. One potential solution is the use of antimicrobial peptides (AMPs). We aimed to design and evaluate a novel, short, and compositionally simple AMP with potent activity against various bacterial pathogens in aquaculture. The resulting peptide, KK12YW, has an amphipathic nature and net charge of + 7. Molecular docking experiments disclosed that KK12YW has a strong affinity for aerolysin, a virulence protein produced by the bacterial pathogen Aeromonas sobria. KK12YW was synthesized using Fmoc chemistry and tested against a range of bacterial pathogens, including A. sobria, A. salmonicida, A. hydrophila, Edwardsiella tarda, Vibrio parahaemolyticus, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, and methicillin-resistant S. aureus. The AMP showed promising antibacterial activity, with MIC and MBC values ranging from 0.89 to 917.1 µgmL-1 and 3.67 to 1100.52 µgmL-1, respectively. In addition, KK12YW exhibited resistance to high temperatures and remained effective even in the presence of serum and salt, indicating its stability. The peptide also demonstrated minimal hemolysis toward fish RBCs, even at higher concentrations. Taken together, these findings indicate that KK12YW could be a highly promising and viable substitute for conventional antibiotics to combat microbial infections in aquaculture.

The amphipathic design in helical antimicrobial peptides

Amphipathicity is a critical characteristic of helical antimicrobial peptides (AMPs). The hydrophilic region, primarily composed of cationic residues, plays a pivotal role in the initial binding to negatively charged components on bacterial membranes through electrostatic interactions. Subsequently, the hydrophobic region interacts with hydrophobic components, inducing membrane perturbation, ultimately leading to cell death, or inhibiting intracellular function. Due to the extensive diversity of natural and synthetic AMPs with regard to the design of amphipathicity, it is complicated to study the structure-activity relationships. Therefore, this work aims to categorize the common amphipathic design and investigate their impact on the biological properties of AMPs. Besides, the connection between current structural modification approaches and amphipathic styles was also discussed.

Study of the Membrane Activity of the Synthetic Peptide ∆M3 Against Extended-Spectrum β-lactamase Escherichia coli Isolates

Escherichia coli is the most common microorganism causing nosocomial or community-acquired bacteremia, and extended-spectrum β-lactamase-producing Escherichia coli isolates are identified worldwide with increasing frequency. For this reason, it is necessary to evaluate potential new molecules like antimicrobial peptides. They are recognized for their biological potential which makes them promising candidates in the fight against infections. The goal of this research was to evaluate the potential of the synthetic peptide ΔM3 on several extended-spectrum β-lactamase producing E. coli isolates. The antimicrobial and cytotoxic activity of the peptide was spectrophotometrically determined. Additionally, the capacity of the peptide to interact with the bacterial membrane was monitored by fluorescence microscopy and infrared spectroscopy. The results demonstrated that the synthetic peptide is active against Escherichia coli isolates at concentrations similar to Meropenem. On the other hand, no cytotoxic effect was observed in HaCaT keratinocyte cells even at 10 times the minimal inhibitory concentration. Microscopy results showed a permeabilizing effect of the peptide on the bacteria. The infrared results showed that ΔM3 showed affinity for the lipids of the microorganism's membrane. The results suggest that the ∆M3 interacts with the negatively charged lipids from the E. coli by a disturbing effect on membrane. Finally, the secondary structure experiments of the peptide showed a random structure in solution that did not change during the interaction with the membranes.

Skin secretions of Leptodactylidae (Anura) and their potential applications

The skin of anuran species is a protective barrier against predators and pathogens, showing also chemical defense by substances that represent a potential source for bioactive substances. This review describes the current chemical and biological knowledge from the skin secretions of Leptodactylidae species, one of the most diverse neotropical frog families. These skin secretions reveal a variety of substances such as amines (12), neuropeptides (16), and antimicrobial peptides (72). The amines include histamine and its methylated derivatives, tryptamine derivatives and quaternary amines. The peptides of Leptodactylidae species show molecular weight up to 3364 Da and ocellatins are the most reported. The peptides exhibit commonly glycine (G) or glycine-valine (GV) as C-terminal amino acids, and the most common N-terminal amino acids are glutamic acid (E), lysine (K), and valine (V). The substances from Leptodactylidae species have been evaluated against pathogenic microorganisms, particularly Escherichia coli and Staphylococcus aureus, and the most active peptides showed MIC of 1-15 µM. Furthermore, some compounds showed also pharmacological properties such as immunomodulation, treatment of degenerative diseases, anticancer, and antioxidant. Currently, only 9% of the species in this family have been properly studied, highlighting a large number of unstudied species such as an entire subfamily (Paratelmatobiinae). The ecological context, functions, and evolution of peptides and amines in this family are poorly understood and represent a large field for further exploration.

Differences in Relevant Physicochemical Properties Correlate with Synergistic Activity of Antimicrobial Peptides

With the urgent need for new medical approaches due to increased bacterial resistance to antibiotics, antimicrobial peptides (AMPs) have been considered as potential treatments for infections. Experiments indicate that combinations of several types of AMPs might be even more effective at inhibiting bacterial growth with reduced toxicity and a lower likelihood of inducing bacterial resistance. The molecular mechanisms of AMP-AMP synergistic antimicrobial activity, however, remain not well understood. Here, we present a theoretical approach that allows us to relate the physicochemical properties of AMPs and their antimicrobial cooperativity. It utilizes correlation and bioinformatics analysis. A concept of physicochemical similarity is introduced, and it is found that less similar AMPs with respect to certain physicochemical properties lead to greater synergy because of their complementary antibacterial actions. The analysis of correlations between the similarity and the antimicrobial properties allows us to effectively separate synergistic from nonsynergistic AMP pairs. Our theoretical approach can be used for the rational design of more effective AMP combinations for specific bacterial targets, for clarifying the mechanisms of bacterial elimination, and for a better understanding of cooperativity phenomena in biological systems.

A rationally engineered small antimicrobial peptide with potent antibacterial activity

Antimicrobial resistance (AMR) is a silent pandemic declared by the WHO that requires urgent attention in the post-COVID world. AMR is a critical public health concern worldwide, potentially affecting people at different stages of life, including the veterinary and agriculture industries. Notably, very few new-age antimicrobial agents are in the current developmental pipeline. Thus, the design, discovery, and development of new antimicrobial agents are required to address the menace of AMR. Antimicrobial peptides (AMPs) are an important class of antimicrobial agents for combating AMR due to their broad-spectrum activity and ability to evade AMR through a multimodal mechanism of action. However, molecular size, aggregability, proteolytic degradation, cytotoxicity, and hemolysis activity significantly limit the clinical application of natural AMPs. The de novo design and engineering of a short synthetic amphipathic AMP (≤16 aa, Mol. Wt. ≤ 2 kDa) with an unusual architecture comprised of coded and noncoded amino acids (NCAAs) is presented here, which demonstrates potent antibacterial activity against a few selected bacterial strains mentioned in the WHO priority list. The designer AMP is conformationally ordered in solution and effectively permeabilizes the outer and inner membranes, leading to bacterial growth inhibition and death. Additionally, the peptide is resistant to proteolysis and has negligible cytotoxicity and hemolysis activity up to 150 μM toward cultured human cell lines and erythrocytes. The designer AMP is unique and appears to be a potent therapeutic candidate, which can be subsequently subjected to preclinical studies to explicitly understand and address the menace of AMR.

Distinct mode of action of a highly stable, engineered phage lysin killing Gram-negative bacteria

IMPORTANCE

Engineered lysins are considered as highly promising alternatives for antibiotics. Our previous screening study using VersaTile technology identified 1D10 as a possible lead compound with activity against Acinetobacter baumannii strains under elevated human serum concentrations. In this manuscript, we reveal an unexpected mode of action and exceptional thermoresistance for lysin 1D10. Our findings shed new light on the development of engineered lysins, providing valuable insights for future research in this field.

Detection of heat-stable antibacterial activity in cotyledonary and discoid placentas

The placenta serves in immunological defense of the fetus, providing proteins essential for innate immunity. Maternal and fetal portions of two mammalian placenta types, discoid, and cotyledonary, were separated and analyzed for antibacterial activity using a culture-independent method. Antibacterial activity was detected in both maternal and fetal portions of all placenta types tested. Protease resistance and increased activity after boiling suggests that the factor is activated upon release from a larger molecule. Identification of this factor and the mechanism of activation will lead to a better understanding of the innate immune function provided by the placenta.

Increasing Heterogeneity in Antimicrobial Peptide Combinations Enhances Their Synergistic Activities

Antimicrobial peptides (AMPs) are short biopolymers produced by living organisms as an immune system defense against infections. They have been considered as potential alternatives to conventional antibiotics. Experiments suggest that combining several types of different AMPs might enhance their antimicrobial activity more effectively than using single-component AMPs. However, a clear understanding of the underlying microscopic mechanisms is still lacking. We present a theoretical investigation of antibacterial cooperativity mechanisms involving several types of AMPs. It is argued that synergy results from intermolecular interactions when the presence of one type of AMP stimulates the association of another type of AMP to bacteria. It is found that increasing the number of different AMPs in the mixtures increases the number of such interactions, making them more efficient in eliminating infections. Our theoretical framework provides valuable insights into the mechanisms of antimicrobial action.

Assessing the Activity under Different Physico-Chemical Conditions, Digestibility, and Innocuity of a GAPDH-Related Fish Antimicrobial Peptide and Analogs Thereof

The antimicrobial activity of SJGAP (skipjack tuna GAPDH-related antimicrobial peptide) and four chemical analogs thereof was determined under different physicochemical conditions, including different pH values, the presence of monovalent and divalent cations, and after a heating treatment. The toxicity of these five peptides was also studied with hemolytic activity assays, while their stability under human gastrointestinal conditions was evaluated using a dynamic in vitro digestion model and chromatographic and mass spectrometric analyses. The antibacterial activity of all analogs was found to be inhibited by the presence of divalent cations, while monovalent cations had a much less pronounced impact, even promoting the activity of the native SJGAP. The peptides were also more active at acidic pH values, but they did not all show the same stability following a heat treatment. SJGAP and its analogs did not show significant hemolytic activity (except for one of the analogs at a concentration equivalent to 64 times that of its minimum inhibitory concentration), and the two analogs whose digestibility was studied degraded very rapidly once they entered the stomach compartment of the digestion model. This study highlights for the first time the characteristics of antimicrobial peptides from Scombridae or homologous to GAPDH that are directly related to their potential clinical or food applications.

Synergistic Effect, Improved Cell Selectivity, and Elucidating the Action Mechanism of Antimicrobial Peptide YS12

Antimicrobial peptides (AMPs) have attracted considerable attention as potential substitutes for traditional antibiotics. In our previous research, a novel antimicrobial peptide YS12 derived from the Bacillus velezensis strain showed broad-spectrum antimicrobial activity against Gram-positive and Gram-negative bacteria. In this study, the fractional inhibitory concentration index (FICI) indicated that combining YS12 with commercial antibiotics produced a synergistic effect. Following these findings, the combination of YS12 with an antibiotic resulted in a faster killing effect against bacterial strains compared to the treatment with the peptide YS12 or antibiotic alone. The peptide YS12 maintained its antimicrobial activity under different physiological salts (Na+, Mg2+, and Fe3+). Most importantly, YS12 exhibited no cytotoxicity towards Raw 264.7 cells and showed low hemolytic activity, whereas positive control melittin indicated extremely high toxicity. In terms of mode of action, we found that peptide YS12 was able to bind with LPS through electrostatic interaction. The results from fluorescent measurement revealed that peptide YS12 damaged the integrity of the bacterial membrane. Confocal laser microscopy further confirmed that the localization of peptide YS12 was almost in the cytoplasm of the cells. Peptide YS12 also exhibited anti-inflammatory activity by reducing the release of LPS-induced pro-inflammatory mediators such as TNF-α, IL-1β, and NO. Collectively, these properties strongly suggest that the antimicrobial peptide YS12 may be a promising candidate for treating microbial infections and inflammation.

Synergistic effect of ultrasound and antimicrobial solutions of cecropin P1 in the deactivation of Escherichia coli O157:H7 using a cylindrical ultrasonic system

This study investigates the synergistic effect of ultrasonication and antimicrobial action of antimicrobial peptide cecropin P1 on the inactivation of Escherichia coli O157:H7 in a cylindrical ultrasonication system. The inactivation of E. coli at pH 7.4 was performed using: ultrasonication (14, 22, and 47 kHz), cecropin P1 (20 µg/mL), and a combination of both. We found the treatment at 22 kHz, 8W for 15 min of exposure and a combination of ultrasound at higher frequency (47 kHz, 8 W) and cecropin P1 for one minute of exposure were more efficient, reducing the cell density by six orders of magnitude, compared to individual treatments (ultrasound or cecropin P1 only). Dye leakage studies and transmission electron microscopy further validated these results. A continuous flow system was designed to demonstrate synergism of ultrasonication with antimicrobial peptide Cecropin P1 in the inactivation of E. coli; synergism was shown to be more at higher ultrasonication frequencies and power levels. Acoustic cavitation by ultrasonic treatment could drastically improve microbial deactivation by antimicrobial peptides cecropin P1 by increasing their ability for pore formation in cell membranes. A continuous ultrasonication and antimicrobial peptides system can lead to an energy-efficient and economical sterilization system for food safety applications.

Evaluation of Antituberculosis Activity and in Silico Properties of Oxymethylene-cyclo-1,3-diones

Tuberculosis is a leading infectious disease that has infected one-third of the world's population and is more prevalent among people belonging to developing countries such as India and China. In the present study, a series of substituted oxymethylene-cyclo-1,3-diones was synthesized and screened for anti-tuberculosis activity against Mycobacterium tuberculosis H37Rv (M. tuberculosis). The compounds were synthesized by condensation of 1,3-cyclicdione, substituted phenols/ alcohols and triethyl orthoformate. The synthesized compounds were screened for anti-tuberculosis activity against M.tuberculosis H37Rv using Middlebrook 7H9 broth assay. Results demonstrated that among the synthesized library of molecules, two compounds 2-(2-hydroxyphenoxymethylene)-5,5-dimethylcyclohexane-1,3-dione and 5,5-dimethyl-2-(2-trifluoromethylphenoxymethylene)cyclohexane-1,3-dione were found to be most active against M. tuberculosis (MICs of 1.25 μg/mL-1 ). The MICs of 2-(2,4-difluoro-phenoxymethylene)-5,5-dimethylcyclohexane-1,3-dione and 2-(2-bromophenoxymethylene)-5,5-dimethylcyclohexane-1,3-dione were found to be 5 and 10 μg mL-1 , respectively. Data from the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed that all the four most active compounds did not exhibit cytotoxicity against human cell lines. Molecular docking studies revealed that the most active compound targets mycobacterial InhA enzyme. In summary, the present study demonstrates the methodology for the synthesis of oxymethylene-cyclo-1,3-diones and identified two potential anti-tuberculosis compounds.

Diversity of Antimicrobial Peptides in Silkworm

Antimicrobial resistance is a phenomenon that the present-day world is witnessing that poses a serious threat to global health. The decline in the development of novel therapeutics over the last couple of decades has exacerbated the situation further. In this scenario, the pursuit of new alternative therapeutics to commonly used antibiotics has gained predominance amongst researchers across the world. Antimicrobial peptides (AMPs) from natural sources have drawn significant interest in the recent years as promising pharmacological substitutes over the conventional antibiotics. The most notable advantage of AMPs is that microorganisms cannot develop resistance to them. Insects represent one of the potential sources of AMPs, which are synthesized as part of an innate immune defence against invading pathogens. AMPs from different insects have been extensively studied, and silkworm is one of them. Diverse classes of AMPs (including attacins, cecropins, defensins, enbocins, gloverins, lebocins and moricins) were identified from silkworm that exhibit antimicrobial property against bacteria, fungi and viruses, indicating their potential therapeutic benefits. This review briefs about the immune responses of silkworm to invading pathogens, the isolation of AMPs from silkworms, AMPs reported in silkworms and their activity against various microorganisms.

Machine learning and molecular simulation ascertain antimicrobial peptide against Klebsiella pneumoniae from public database

Antimicrobial peptides (AMPs) are short peptides with a broad spectrum of antimicrobial activity. They play a key role in the host innate immunity of many organisms. The growing threat of microorganisms resistant to antimicrobial agents and the lack of new commercially available antibiotics have made in silico discovery of AMPs increasingly important. Machine learning (ML) has improved the speed and efficiency of AMP discovery while reducing the cost of experimental approaches. Despite various ML platforms developed, there is still a lack of integrative use of ML platforms for AMP discovery from publicly available protein databases. Therefore, our study aims to screen potential AMPs with antibiofilm properties from databases using ML platforms, followed by protein-peptide molecular docking analysis and molecular dynamics (MD) simulations. A total of 5850 peptides classified as non-AMP were screened from UniProtKB and analyzed using various online ML platforms (e.g., CAMPr3, DBAASP, dPABBs, Hemopred, and ToxinPred). Eight potential AMP peptides against Klebsiella pneumoniae with antibiofilm, non-toxic and non-hemolytic properties were then docked to MrkH, a transcriptional regulator of type 3 fimbriae involved in biofilm formation. Five of eight peptides bound more strongly than the native MrkH ligand when analyzed using HADDOCK and HPEPDOCK. Following the docking studies, our MD simulated that a Neuropeptide B (Peptide 3) bind strongly to the MrkH active sites. The discovery of putative AMPs that exceed the binding energies of the native ligand underscores the utility of the combined ML and molecular simulation strategies for discovering novel AMPs with antibiofilm properties.

Advancements, challenges and future perspectives on peptide-based drugs: Focus on antimicrobial peptides

Among other health related issues, the rising concerns on drug resistance led to look for alternative pharmaceutical drugs that are effective both against infectious and noninfectious diseases. Antimicrobial peptides (AMPs) emerged as potential therapeutic molecule with wide range of applications. With their limitations, AMPs have gained reputable attentions in research as well as in the pharmaceutical industry. This review highlighted the historical background, research trends, technological advancements, challenges, and future perspectives in the development and applications of peptide drugs. Some vital questions related with the need for pharmaceutical production, factors for the slow and steady journey, the importance of oral bioavailability, and the drug resistance possibilities of AMPs were raised and addressed accordingly. Therefore, the current study is believed to provide a profound understanding in the past and current scenarios and future directions on the therapeutic impacts of peptide drugs.

Plasticity and Stereotypic Rewiring of the Transcriptome Upon Bacterial Evolution of Antibiotic Resistance

Bacterial evolution of antibiotic resistance frequently has deleterious side effects on microbial growth, virulence, and susceptibility to other antimicrobial agents. However, it is unclear how these trade-offs could be utilized for manipulating antibiotic resistance in the clinic, not least because the underlying molecular mechanisms are poorly understood. Using laboratory evolution, we demonstrate that clinically relevant resistance mutations in Escherichia coli constitutively rewire a large fraction of the transcriptome in a repeatable and stereotypic manner. Strikingly, lineages adapted to functionally distinct antibiotics and having no resistance mutations in common show a wide range of parallel gene expression changes that alter oxidative stress response, iron homeostasis, and the composition of the bacterial outer membrane and cell surface. These common physiological alterations are associated with changes in cell morphology and enhanced sensitivity to antimicrobial peptides. Finally, the constitutive transcriptomic changes induced by resistance mutations are largely distinct from those induced by antibiotic stresses in the wild type. This indicates a limited role for genetic assimilation of the induced antibiotic stress response during resistance evolution. Our work suggests that diverse resistance mutations converge on similar global transcriptomic states that shape genetic susceptibility to antimicrobial compounds.

The Potential of Surface-Immobilized Antimicrobial Peptides for the Enhancement of Orthopaedic Medical Devices: A Review

Due to the well-known phenomenon of antibiotic resistance, there is a constant need for antibiotics with novel mechanisms and different targets respect to those currently in use. In this regard, the antimicrobial peptides (AMPs) seem very promising by virtue of their bactericidal action, based on membrane permeabilization of susceptible microbes. Thanks to this feature, AMPs have a broad activity spectrum, including antibiotic-resistant strains, and microbial biofilms. Additionally, several AMPs display properties that can help tissue regeneration. A possible interesting field of application for AMPs is the development of antimicrobial coatings for implantable medical devices (e.g., orthopaedic prostheses) to prevent device-related infection. In this review, we will take note of the state of the art of AMP-based coatings for orthopaedic prostheses. We will review the most recent studies by focusing on covalently linked AMPs to titanium, their antimicrobial efficacy and plausible mode of action, and cytocompatibility. We will try to extrapolate some general rules for structure-activity (orientation, density) relationships, in order to identify the most suitable physical and chemical features of peptide candidates, and to optimize the coupling strategies to obtain antimicrobial surfaces with improved biological performance.

Bactericidal Properties of Proline-Rich Aedes aegypti Trypsin Modulating Oostatic Factor (AeaTMOF)

The antimicrobial properties of proline-rich Aedes aegypti decapeptide TMOF (AeaTMOF) and oncocin112 (1-13) were compared. Incubations with multidrug-resistant Escherichia coli cells showed that AeaTMOF (5 mM) was able to completely inhibit bacterial cell growth, whereas oncocin112 (1-13) (20 mM) partially inhibited bacterial growth as compared with bacterial cells that were not multidrug-resistant cells. AeaTMOF (5 mM) was very effective against Acinetobacter baumannii and Pseudomonas aeruginosa, completely inhibiting cell growth during 15 h incubations. AeaTMOF (5 mM) completely inhibited the Gram-positive bacteria Staphylococcus aureus and Bacillus thurengiensis sups. Israelensis cell growth, whereas oncocin112 (1-13) (10 and 20 mM) failed to affect bacterial cell growth. E. coli cells that lack the SbmA transporter were inhibited by AeaTMOF (5 mM) and not by oncocin112 (1-13) (10 to 20 mM), indicating that AeaTMOF can use other bacterial transporters than SbmA that is mainly used by proline-rich antimicrobial peptides. Incubation of E. coli cells with NaAzide showed that AeaTMOF does not use ABC-like transporters that use ATP hydrolysis to import molecules into bacterial cells. Three-dimensional modeling and docking of AeaTMOF to SbmA and MdtM transporters showed that AeaTMOF can bind these proteins, and the binding location of AeaTMOF inside these protein transporters allows AeaTMOF to be transported into the bacterial cytosol. These results show that AeaTMOF can be used as a future antibacterial agent against both multidrug-resistant Gram-positive and -negative bacteria.

Activity and Synergy of Cu-ATCUN Antimicrobial Peptides

Antibiotic resistance demands innovative strategies and therapies. The pairs of antimicrobial peptides tested in this work show broad-spectrum synergy and are capable of interacting with diverse bacterial membranes. In most cases, the ATCUN motif enhanced the activity of peptides tested in combination. Our studies also show CP10A to be a multifaceted peptide, displaying both cell membrane and intracellular activity and acting as a chameleon, improving the activity of other peptides as needed. The results of the synergy experiments demonstrate the importance of varied modes of action and how these changes can affect the ability to combat pathogens, while also illustrating the value of the metal-binding domain in enhancing the activity of antimicrobial peptides in combination.

Cooperativity in Bacterial Membrane Association Controls the Synergistic Activities of Antimicrobial Peptides

Antimicrobial peptides (AMPs), or defence peptides, are compounds naturally produced during immune responses of living organisms against bacterial infections that are currently actively considered as promising alternatives to antibiotics. Recent experimental studies uncovered that in many situations, combinations of different AMPs are much more successful in eliminating the bacterial pathogens than single peptide species. However, the microscopic origin of such synergistic activities remains not fully understood. We present and investigate a possible mechanism of synergy between AMPs. It is based on the idea that due to inter-molecular interactions, the presence of an AMP of one type stimulates the association of an AMP of another type, and this accelerates the overall association to the membrane, eventually killing the bacteria. This approach allows us to fully quantify the synergistic activities of AMPs, and it is successfully applied for several experimental systems. It is found that strong cooperativity can be achieved for relatively weak inter-molecular interactions, suggesting that the application of combinations of AMPs can be further rationally optimized to make it a powerful antibacterial treatment.

Mass Spectrometry-Based Peptide Profiling of Haemolymph from Pterostichus melas Exposed to Pendimethalin Herbicide

Pendimethalin-based herbicides are used worldwide for pre-emergence selective control of annual grasses and weeds in croplands. The endurance of herbicides residues in the environment has an impact on the soil biodiversity and fertility, also affecting non-target species, including terrestrial invertebrates. Carabid beetles are known as natural pest control agents in the soil food web of agroecosystems, and feed on invertebrates and weed seeds. Here, a mass spectrometry untargeted profiling of haemolymph is used to investigate Pterostichus melas metabolic response after to pendimethalin-based herbicide exposure. Mass spectrometric data are examined with statistical approaches, such as principal component analysis, for possible correlation with biological effects. Those signals with high correlation are submitted to tandem mass spectrometry to identify the associated biomarker. The time course exposure showed many interesting findings, including a significant downregulation of related to immune and defense peptides (M-lycotoxin-Ls4a, Peptide hormone 1, Paralytic peptide 2, and Serine protease inhibitor 2). Overall, the observed peptide deregulations concur with the general mechanism of uptake and elimination of toxicants reported for Arthropods.

The Role of Gut Microbiota in Some Liver Diseases: From an Immunological Perspective

Gut microbiota is a microecosystem composed of various microorganisms. It plays an important role in human metabolism, and its metabolites affect different tissues and organs. Intestinal flora maintains the intestinal mucosal barrier and interacts with the immune system. The liver is closely linked to the intestine by the gut-liver axis. As the first organ that comes into contact with blood from the intestine, the liver will be deeply influenced by the gut microbiota and its metabolites, and the intestinal leakage and the imbalance of the flora are the trigger of the pathological reaction of the liver. In this paper, we discuss the role of gut microbiota and its metabolites in the pathogenesis and development of autoimmune liver diseases((including autoimmune hepatitis, primary biliary cirrhosis, primary sclerosing cholangitis), metabolic liver disease such as non-alcoholic fatty liver disease, cirrhosisits and its complications, and liver cancer from the perspective of immune mechanism. And the recent progress in the treatment of these diseases was reviewed from the perspective of gut microbiota.

Effects of LPS Composition in Escherichia coli on Antibacterial Activity and Bacterial Uptake of Antisense Peptide-PNA Conjugates

The physical and chemical properties of the outer membrane of Gram-negative bacteria including Escherichia coli have a significant impact on the antibacterial activity and uptake of antibiotics, including antimicrobial peptides and antisense peptide-peptide nucleic acid (PNA) conjugates. Using a defined subset of E. coli lipopolysaccharide (LPS) and envelope mutants, components of the LPS-core, which provide differential susceptibility toward a panel of bacterial penetrating peptide (BPP)-PNA conjugates, were identified. Deleting the outer core of the LPS and perturbing the inner core only sensitized the bacteria toward (KFF)₃K-PNA conjugates, but not toward conjugates carrying arginine-based BPPs. Interestingly, the chemical composition of the outer LPS core as such, rather than overall hydrophobicity or surface charge, appears to determine the susceptibility to different BPP-PNA conjugates thereby clearly demonstrating the complexity and specificity of the interaction with the LPS/outer membrane. Notably, mutants with outer membrane changes conferring polymyxin resistance did not show resistance toward the BPP-PNA conjugates, thereby eliminating one possible route of resistance for these molecules. Finally, envelope weakening, through deletion of membrane proteins such as OmpA as well as some proteins previously identified as involved in cationic antimicrobial peptide uptake, did not significantly influence BPP-PNA conjugate activity.

Bio-nano scale modifications of melittin for improving therapeutic efficacy

INTRODUCTION

Melittin (MLT), a natural membrane-active component, is the most prominent cytolytic peptide from bee venom. Remarkable biological properties of MLT, including anti-inflammatory, antimicrobial, anticancer, anti-protozoan, and antiarthritic activities, make it an up-and-coming therapeutic candidate for a wide variety of human diseases. Therapeutic applications of MLT may be hindered due to low stability, high toxicity, and weak tissue penetration. Different bio-nano scale modifications hold promise for improving its functionality and therapeutic efficacy.

AREAS COVERED

In the current review, we aimed to provide a comprehensive insight into strategies used for MLT conjugations and modifications, cellular delivery of modified forms, and their clinical perspectives by reviewing the published literature on PubMed, Scopus, and Google Scholar databases. We also emphasized the MLT structure modifications, mechanism of action, and cellular toxicity.

EXPERT OPINION

Developing new analogs and conjugates of MLT as a natural drug with improved functions and fewer side effects is crucial for the clinical translation of this approach worldwide, especially where the chemicals and synthetic drugs are more expensive or unavailable in the healthcare system. MLT-nanoconjugation may be one of the best-optimized strategies for improving peptide delivery, increasing its therapeutic efficacy, and providing minimal nonspecific cellular lytic activity. [Figure: see text].

Two Liberibacter Proteins Combine to Suppress Critical Innate Immune Defenses in Citrus

We adopted a systems-based approach to determine the role of two Candidatus Liberibacter asiaticus (CLas) proteins, LasP ₂₃₅ and Effector 3, in Huanglongbing (HLB) pathogenesis. While a published work suggests the involvement of these CLas proteins HLB pathogenesis, the exact structure-based mechanism of their action has not been elucidated. We conducted the following experiments to determine the structure-based mechanisms of action. First, we immunoprecipitated the interacting citrus protein partners of LasP ₂₃₅ and Effector 3 from the healthy and CLas-infected Hamlin extracts and identified them by Liquid Chromatography with tandem mass spectrometry (LC-MS/MS). Second, we performed a split green fluorescent protein (GFP) assay in tobacco to validate that the interactions observed in vitro are also retained in planta. The notable in planta citrus targets of LasP ₂₃₅ and Effector 3 include citrus innate immune proteins. Third, in vitro and in planta studies were performed to show that LasP ₂₃₅ and Effector 3 interact with and inhibit the functions of multiple citrus proteins belonging to the innate immune pathways. These inhibitory interactions led to a high level of reactive oxygen species, blocking of bactericidal lipid transfer protein (LTP), and induction of premature programed cell death (PCD), all of which are beneficial to CLas lifecycle and HLB pathogenesis. Finally, we performed molecular dynamics simulations to visualize the interactions of LasP ₂₃₅ and Effector 3, respectively, with LTP and Kunitz protease inhibitor. This led to the design of an LTP mimic, which sequestered and blocked LasP ₂₃₅ and rescued the bactericidal activity of LTP thereby proving that LasP ₂₃₅ , indeed, participates in HLB pathogenesis.

Targeting foodborne pathogens via surface-functionalized nano-antimicrobials

The incorporation of antibiotics and bioactive compounds into non-toxic nanoparticles has been popularly used to produce effective antimicrobial nanocarriers against foodborne pathogens. These systems can protect antimicrobials against harsh environments, control their release, and increase their antimicrobial activities; however, their functions can be decreased by some major barriers. Intracellular localization of bacteria protects them from the host immune system and antimicrobial agents. Also, bacteria can cause constant infection by nestling in professional phagocytic cells. In the last years, surface functionalization of nanocarriers by passive and active modification methods has been applied for their protection against clearance from the blood, increasing both circulation time and uptake by target cells. For achieving this objective, different functional agents such as specifically targeted peptides internalize ligands, saccharide ligands, or even therapeutic molecules (e.g., antibodies or enzymes) are used. In this review, techniques for functionalizing the surface of antimicrobial-loaded nanocarriers have been described. This article offers a comprehensive review of the potential of functional nanoparticles to increase the performance of antimicrobials against foodborne pathogens through targeting delivery.

Effect and Mechanisms of Antibacterial Peptide Fraction from Mucus of C. aspersum against Escherichia coli NBIMCC 8785

Peptides isolated from the mucus of Cornu aspersum could be prototypes for antibiotics against pathogenic bacteria. Information regarding the mechanisms, effective concentration, and methods of application is an important tool for therapeutic, financial, and ecological regulation and a holistic approach to medical treatment. A peptide fraction with MW < 10 kDa was analyzed by MALDI-TOF-TOF using Autoflex™ III. The strain Escherichia coli NBIMCC 8785 (18 h and 48 h culture) was used. The changes in bacterial structure and metabolic activity were investigated by SEM, fluorescent, and digital image analysis. This peptide fraction had high inhibitory effects in surface and deep inoculations of E. coli of 1990.00 and 136.13 mm2/mgPr/µMol, respectively, in the samples. Thus, it would be effective in the treatment of infections involving bacterial biofilms and homogenous cells. Various deformations of the bacteria and inhibition of its metabolism were discovered and illustrated. The data on the mechanisms of impact of the peptides permitted the formulation of an algorithm for the treatment of infections depending on the phase of their development. The decrease in the therapeutic concentrations will be more sparing to the environment and will lead to a decrease in the cost of the treatment.

Pathogenesis of the Pseudomonas aeruginosa Biofilm: A Review

Pseudomonas aeruginosa is associated with several human infections, mainly related to healthcare services. In the hospital, it is associated with resistance to several antibiotics, which poses a great challenge to therapy. However, one of the biggest challenges in treating P. aeruginosa infections is that related to biofilms. The complex structure of the P. aeruginosa biofilm contributes an additional factor to the pathogenicity of this microorganism, leading to therapeutic failure, in addition to escape from the immune system, and generating chronic infections that are difficult to eradicate. In this review, we address several molecular aspects of the pathogenicity of P. aeruginosa biofilms.

Development of Bactericidal Peptides against Multidrug-Resistant Acinetobacter baumannii with Enhanced Stability and Low Toxicity

Pathogenic superbugs are the root cause of untreatable complex infections with limited or no treatment options. These infections are becoming more common as clinical antibiotics have lost their effectiveness over time. Therefore, the development of novel antibacterial agents is urgently needed to counter these microbes. Antimicrobial peptides (AMPs) are a viable treatment option due to their bactericidal potency against multiple microbial classes. AMPs are naturally selected physiological microbicidal agents that are found in all forms of organisms. In the present study, we developed two tilapia piscidin 2 (TP2)-based AMPs for antimicrobial application. Unlike the parent peptide, the redesigned peptides showed significant antimicrobial activity against multidrug-resistant bacterial species. These peptides also showed minimal cytotoxicity. In addition, they were significantly active in the presence of physiological salts, 50% human serum and elevated temperature. The designed peptides also showed synergistic activity when combined with clinical antibiotics. The current approach demonstrates a fruitful strategy for developing potential AMPs for antimicrobial application. Such AMPs have potential for progression to further trials and drug development investigations.

Isolation and Chemical Characterization of an Alpha-Helical Peptide, Dendrocin-ZM1, Derived from Zataria multiflora Boiss with Potent Antibacterial Activity

Today, resistance of microorganisms to antibiotics has become a major challenge. To overcome this problem, development of new drugs, besides research on their antibacterial activity, is essential. Among chemical components, antimicrobial peptides (AMPs) exhibit antibacterial activity and can be selected as suitable antimicrobial candidates. In this study, a novel antimicrobial peptide, called dendrocin-ZM1, with a molecular weight of ~3716.48 Da, was isolated from Zataria multiflora Boiss (ZM) and purified via precipitation with ammonium sulfate and reverse-phase HPLC chromatography; it was then sequenced via Edman degradation. The in silico method was used to examine the physicochemical properties of dendrocin-ZM1. In this study, four reference strains (gram-positive and gram-negative) and one clinical vancomycin-resistant Staphylococcus aureus strain were used to survey the antimicrobial activities. Moreover, to examine cytotoxicity and hemolytic activity, a HEK-293 cell line and human red blood cells (RBCs) were used, respectively. Evaluation of the physicochemical properties of dendrocin-ZM1, as an AMP, indicated a net charge of + 7 and a hydrophobicity percentage of 54%. This peptide had an amphipathic alpha-helical conformation. It exhibited broad-spectrum antibacterial activities against the tested strains at minimum inhibitory concentrations (MICs) of 4-16 μg/mL. Besides, this peptide showed negligible hemolysis and cytotoxicity in the MIC range. It also exhibited heat stability at temperatures of 20 to 80 °C and was active in a broad pH range (from 6.0 to 10.0). Overall, the present results suggested dendrocin-ZM1 as a remarkable antimicrobial candidate.

Heterologous Expression and Functional Characterization of CAP18 from Oryctolagus cuniculus

BACKGROUND

Antimicrobial peptides belong to the innate defence system of creatures. These peptides attach to the bacterial membrane in order to die microorganisms by penetrating them. Hence, biotechnology researchers pay more attention to produce antimicrobial peptides for use in various fields. The studies showed that rabbit tissue with inflammation and skin ulcers would be producing CAP18 peptide, which belongs to the cathelicidin group.

METHODS

In this study, the optimized sequence of the cap18 gene was placed into the pPICZAα plasmid after the alpha-factor signal and transformed into Pichia pastoris (X-33 strain). Purification of the recombinant peptide was done based on its histidine tail at C-terminal, and western blotting method was used to demonstrate the purification of rCAP18. The antibacterial activity of the purified and desalted rCAP18 was investigated at different concentrations against pathogenic bacteria.

RESULTS

The maximum expression level of rCAP18 (17.5 kDa) was seen 90 h after induction of alcohol oxidase I (AOX1) promoter with methanol. The concentration of rCAP18 was 33 mg/L after purification with Ni-NTA Sepharose column. The function of rCAP18 (4.3, 5.7, 7 µg/ml) was investigated against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Results showed that %CFU/cm² reached 28% after P. aeruginosa cells treatment with 7 μg/ml of rCAP18.

CONCLUSION

This study presented the findings related to heterologous expression of cap18 gene, and evaluation of rCAP18 antibacterial effects. Our results showed that rCAP18 plays a significant role in inhibiting bacterial growth, especially Gram-negative bacteria.

Supplementation of zebrafish (Danio rerio) diet using a short antimicrobial peptide: Evaluation of growth performance, immunomodulatory function, antioxidant activity, and disease resistance

Short-chain bioactive peptides are new and promising antimicrobial, immune moderating, and antioxidant agents. Therefore, the present study was conducted to evaluate in vitro antibacterial activity of CM11, a short antimicrobial peptide (AMP), against Streptococcus iniae and Yersinia ruckeri as fish pathogenic bacteria using standard disk diffusion and microdilution assays. In addition, in vivo effects of CM11 on fish growth, immunity, antioxidant activity, and disease resistance were evaluated using zebrafish (Danio rerio) as an animal model. For in vivo study, based on in vitro susceptibility results, four diets were designed to include zero (as control), 10, 20, and 50 μg of CM11 per g diet referred to as control, P1, P2, and P3 treatments, respectively. After eight weeks of dietary trial, fish were challenged with Streptococcus iniae, and the survival rate was calculated for a period of two weeks. Results showed that CM11 effectively inhibited the growth of S. iniae and Y. ruckeri on agar plates at a concentration of eight μg/ml. Minimum inhibitory and minimum bactericidal concentrations of CM11 were measured at 8 and 32 μg/ml for S. iniae and 16 and 64 μg/ml Y. ruckeri, respectively. In vivo results showed no noticeable effects on fish growth parameters, however, feed conversion ratio (FCR) was found lower in P3 and P2 compared to control (P < 0.05). Immunological and antioxidant responses were found strongly affected by CM11 in all treatment groups in which the highest values were found in the P3 treated group. Key immune and antioxidant genes were up-regulated particularly in fish receiving the highest level of CM11 (P3). Fish receiving the CM11 peptide showed better survival when challenged with S. iniae. These findings suggest the potential of CM11 for use in aquaculture as an antibacterial and immunostimulant agent.

Antimicrobial activity, environmental sensitivity, mechanism of action, and food application of αs165-181 peptide

αs165-181 is a peptide derived from αs₂-casein of ovine milk. Herein, we report the antimicrobial activity and mechanism, and food application of the peptide. αs165-181 showed antimicrobial activity against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Listeria monocytogenes, Bacillus cereus, and Salmonella enterica serovar Enteritidis in a dose-dependent manner. The minimum inhibitory concentration of the peptide was 3.9 mg/ml for E. coli and 7.8 mg/ml for the other bacteria. The peptide did not show antimicrobial activity against Lactobacillus plantarum up to 3.9 mg/ml concentration. The minimum bactericidal concentration of αs165-181 peptide was 7.8 mg/ml for E. coli, S. aureus, L. monocytogenes, and B. cereus. The peptide was sensitive to monovalent and divalent cations, pH, and high temperatures. Transmission electron microscopy, cytoplasmic β-galactosidase leakage, and DNA electrophoresis analyses showed that αs165-181 peptide affects bacteria by damaging cell membrane and binding to the genomic DNA. When αs165-181 peptide was applied to minced beef or UHT cream, the antimicrobial activity (7.8 mg/g) was almost the same as or even better than nisin (0.5 mg/g). This study helps understand the antimicrobial mode of action of αs165-181 peptide and develop strategies for application in food products.

The Kinocidin Interleukin-26 Shows Immediate Antimicrobial Effects Even to Multi-resistant Isolates

The cationic proinflammatory cytokine Interleukin 26 (IL-26) shows antibacterial activity and inhibits the replication of cytomegalovirus and hepatitis C virus. This study evaluates the early microbicidal activities of IL-26 against major bacterial species including multi-resistant variants and Candida albicans. Recombinant IL-26 was bacterially expressed and studied for its microbicidal effects in culture. We show that IL-26 has strong 90% bactericidal activities against Enterococcus faecalis, Enterococcus faecium, Staphylococcus aureus, and Acinetobacter baumannii. Similarly, IL-26 sensitivity was also detectable in vancomycin-resistant Enterococcus species, methicillin-resistant S. aureus, and carbapenem-resistant A. baumannii clinical isolates. Additionally, a significant, albeit weak fungicidal effect against Candida albicans was observed. Activities against Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa were not detectable. The proinflammatory cytokine and kinocidin IL-26 shows strong bactericidal activities against A. baumannii and, almost selectively, against Gram-positive bacteria.

Genome-scale identification of plant defensin (PDF) family genes and molecular characterization of their responses to diverse nutrient stresses in allotetraploid rapeseed

Plant defensins (PDFs), short peptides with strong antibacterial activity, play important roles in plant growth, development, and stress resistance. However, there are few systematic analyses on PDFs in Brassica napus. Here, bioinformatics methods were used to identify genome-wide PDFs in Brassica napus, and systematically analyze physicochemical properties, expansion pattern, phylogeny, and expression profiling of BnaPDFs under diverse nutrient stresses. A total of 37 full-length PDF homologs, divided into two subgroups (PDF1s and PDF2s), were identified in the rapeseed genome. A total of two distinct clades were identified in the BnaPDF phylogeny. Clade specific conserved motifs were identified within each clade respectively. Most BnaPDFs were proved to undergo powerful purified selection. The PDF members had enriched cis-elements related to growth and development, hormone response, environmental stress response in their promoter regions. GO annotations indicate that the functional pathways of BnaPDFs are mainly involved in cells killing and plant defense responses. In addition, bna-miRNA164 and bna-miRNA172 respectively regulate the expression of their targets BnaA2.PDF2.5 and BnaC7.PDF2.6. The expression patterns of BnaPDFs were analyzed in different tissues. BnaPDF1.2bs was mainly expressed in the roots, whereas BnaPDF2.2s and BnaPDF2.3s were both expressed in stamen, pericarp, silique, and stem. However, the other BnaPDF members showed low expression levels in various tissues. Differential expression of BnaPDFs under nitrate limitation, ammonium excess, phosphorus starvation, potassium deficiency, cadmium toxicity, and salt stress indicated that they might participate in different nutrient stress resistance. The genome-wide identification and characterization of BnaPDFs will enrich understanding of their molecular characteristics and provide elite gene resources for genetic improvement of rapeseed resistance to nutrient stresses.

Virus-inspired designs of antimicrobial nanocapsules

Antimicrobial resistance is becoming a serious burden for drug design. The challenges are in finding novel approaches for effectively targeting a number of different bacterial strains, and in delivering these to the site of action. We propose here a novel approach that exploits the assembly of antimicrobial peptidic units in nanocapsules that can penetrate and rupture the bacterial membrane. Additionally, the chemical versatility of the designed units can be tailored to specific targets and to the delivery of genetic material in the cell. The proposed design exploits a β-annulus (sequence ITHVGGVGGSIMAPVAVSRQLVGS) triskelion unit from the Tomato Bushy Stunt Virus, able to self assemble in solution, and functionalised with antimicrobial sequences to form dodecahedral antimicrobial nanocapsules. The stability and the activity of the antimicrobial β-annulus capsule is measured by molecular dynamics simulations in water and in the presence of model membranes.