Multiple Mechanisms of the Synthesized Antimicrobial Peptide TS against Gram-Negative Bacteria for High Efficacy Antibacterial Action In Vivo

Interaction of Cecropin A (1-7) Analogs with DNA Analyzed by Multi-spectroscopic Methods

Cecropin A (1-7) is a cationic antimicrobial peptide which contain lots of basic amino acids. To understand the effect of basic amino acids on cecropin A (1-7), analogues CA2, CA3 and CA4 which have more arginine or lysine at the N-terminal or C-terminal were designed and synthesized. The interaction of cecropin A (1-7) and its analogs with DNA was studied using ultraviolet-visible spectroscopy, fluorescence spectroscopy and circular dichroism spectroscopy. Multispectral analysis showed that basic amino acids improved the interaction between the analogues and DNA. The interaction between CA4 and DNA is most pronounced. Fluorescence spectrum indicated that Ksv value of CA4 is 1.19 × 105  L mol-1 compared to original peptide cecropin A (1-7) of 3.73 × 104  L mol-1. The results of antimicrobial experiments with cecropin A (1-7) and its analogues showed that basic amino acids enhanced the antimicrobial effect of the analogues. The antimicrobial activity of CA4 against E. coli was eightfold higher than that of cecropin A (1-7). The importance of basic amino acid in peptides is revealed and provides useful information for subsequent studies of antimicrobial peptides.

The antibacterial activity and mechanism of a novel peptide MR-22 against multidrug-resistant Escherichia coli

Introduction

Bacterial infections have become serious threats to human health, and the excessive use of antibiotics has led to the emergence of multidrug-resistant (MDR) bacteria. E. coli is a human bacterial pathogen, which can cause severe infectious. Antimicrobial peptides are considered the most promising alternative to traditional antibiotics.

Materials and methods

The minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and hemolytic activity were determined by the microdilution method. The antimicrobial kinetics of MR-22 against E. coli were studied by growth curves and time-killing curves. The cytotoxicity of MR-22 was detected by the CCK-8 assay. The antimicrobial activity of MR-22 in salt, serum, heat and trypsin was determined by the microdilution method. The antimicrobial mechanism of MR-22 against drug-resistant E. coli was studied by Scanning Electron Microscope, laser confocal microscopy, and Flow Cytometry. The in vivo antibacterial activity of MR-22 was evaluated by the mice model of peritonitis.

Results and discussion

In this study, MR-22 is a new antimicrobial peptide with good activity that has demonstrated against MDR E. coli. The antimicrobial activity of MR-22 exhibited stability under conditions of high temperature, 10% FBS, and Ca2+. However, a decline of the activity was observed in the presence of Na+, serum, and trypsin. MR-22 had no significant cytotoxicity or hemolysis in vitro. SEM and fluorescent images revealed that MR-22 could disrupt the integrity of cell membrane. DCFH-DA indicated that MR-22 increased the content of reactive oxygen species, while it decreased the content of intracellular ATP. In mice model of peritonitis, MR-22 exhibited potent antibacterial activity in vivo. These results indicated that MR-22 is a potential drug candidate against drug-resistant E. coli.

Lacticaseibacillus paracasei fermentation broth identified peptide, Y2Fr, and its antibacterial activity on Vibrio parahaemolyticus

Although Vibrio parahaemolyticus infections cause severe diseases of large yellow croaker (Larimichthys crocea), using antibiotics and other chemical agents to treat these infections could result in antimicrobial resistance, environmental pollution, and other associated problems. This study identified seven peptides from Lacticaseibacillus paracasei fermentation broth using ultra-high-performance liquid chromatography-mass spectrometry and screened antimicrobial peptide Y2Fr (VEIKNGLLKLNGKPLLIR) through its net charge, hydrophobicity and predicted secondary structure. Antibacterial activity analysis revealed that Y2Fr had a minimum inhibitory concentration (MIC) of 125 μg/mL, minimum bactericidal concentration (MBC) of 250 μg/mL against V. parahaemolyticus and a time-kill of 3 h. In a bacterial membrane environment, the secondary structure of peptide Y2Fr changed from a random coil to a β-sheet to enhance its membrane permeability and binding to bacteria DNA to exert its antibacterial effect. Further molecular docking analysis revealed that peptide Y2Fr could bind to the membrane protein KKI11460.1 and DNA polymerase A0A0L8TVA4 of V. parahaemolyticus through hydrogen bonds. Meanwhile, treatment of Y2Fr with mammalian red blood cells and plasma revealed that it was noncytotoxic, nonhemolytic, and stable under physiological conditions. Thus, peptide Y2Fr has great potential use in treating and preventing infections caused by V. parahaemolyticus or similar bacteria in aquatic animals.

Antimicrobial peptides as drugs with double response against Mycobacterium tuberculosis coinfections in lung cancer

Tuberculosis and lung cancer are, in many cases, correlated diseases that can be confused because they have similar symptoms. Many meta-analyses have proven that there is a greater chance of developing lung cancer in patients who have active pulmonary tuberculosis. It is, therefore, important to monitor the patient for a long time after recovery and search for combined therapies that can treat both diseases, as well as face the great problem of drug resistance. Peptides are molecules derived from the breakdown of proteins, and the membranolytic class is already being studied. It has been proposed that these molecules destabilize cellular homeostasis, performing a dual antimicrobial and anticancer function and offering several possibilities of adaptation for adequate delivery and action. In this review, we focus on two important reason for the use of multifunctional peptides or peptides, namely the double activity and no harmful effects on humans. We review some of the main antimicrobial and anti-inflammatory bioactive peptides and highlight four that have anti-tuberculosis and anti-cancer activity, which may contribute to obtaining drugs with this dual functionality.

Interaction of bifunctional peptide-carbazole complexes with DNA and antimicrobial activity

Two peptide-carbazole conjugates, CTAT and CNLS, were designed and synthesized using carbazole Schiff base to modify the cell membrane penetrating peptide TAT (47-57) and the nuclear localization peptide NLS at the N terminus. The interaction with ctDNA was investigated by multispectral and agarose gel electrophoresis. And the effects of CNLS and CTAT on the G-quadruplex structure were explored by circular dichroism titration experiments. The results show that both CTAT and CNLS interact with ctDNA in a minor groove binding manner. Both conjugates bind more tightly to DNA than the individual substances CIBA, TAT and NLS. In addition, CTAT and CNLS are capable of unfolding parallel G-quadruplex structures and are potential G-quadruplex unfolding agents. Finally, broth microdilution was performed to test the antimicrobial activity of the peptides. The results showed that CTAT and CNLS had a 4-fold increase in antimicrobial activity compared with the parent peptides TAT and NLS. They could exert antimicrobial activity by disrupting the integrity of cell membrane bilayer and binding to DNA, and could be used as novel antimicrobial peptides for the development of novel antimicrobial antibiotics.

Structural Analysis and Antimicrobial Mechanism of a Protein GBSPI-A from Ginkgo Biloba Seed

Ginkgo biloba seed has antimicrobial activity. In this study, ginkgo biloba seed protein was prepared, identified, and named GBSPI-A, finding its construction was similar to 11-S globulin. Then, the influence of GBSPI-A on the cell membrane and physiological metabolism of K. pneumoniae and S. aureus were investigated. The results showed that GBSPI-A (20 mg/mL) destroyed the cell membrane, causing leakage of intracellular material and inhibited bacterial growth with an inhibition rate of approximately 80%. In addition, the GBSPI-A (10 mg/mL) caused the decreasing activity of ATPase and respiratory rate, and the respiratory depression rate was 7.24%. Furthermore, the decreasing ATP synthesis and intracellular β-galactosidase activity led to an insufficient supply of physiological metabolic energy. Therefore, the results showed that GBSPI-A could be used as a natural bacteriostatic agent to replace related drugs and also provide a new insight into the application of GBSPI-A in food safety.

The Role of Methyl-(Z)-11-tetradecenoate Acid from the Bacterial Membrane Lipid Composition in Escherichia coli Antibiotic Resistance

Background

The bacterial membrane plays a critical role in the survival of bacteria and the effectiveness of antimicrobial peptides in protecting the host. The lipid constituents of the bacterial membrane are not evenly distributed, and they could be affected by clustering anionic lipids with cationic peptides with multiple positive charges. That could be harmful to bacteria because it prevents lipids from interacting with other molecular components of the cell membrane, disrupts existing natural domains, or creates phase boundary defects between the clustered lipids and the bulk of the membrane. This preliminary quantitative study is aimed at assembling a correlation between antibiotic resistance and bacterial lipid composition in E. coli, based on the function and arrangement of the bilipid coating of the bacterial cell, intimately associated with the path of antimicrobials through membranes.

Methods

Fifteen multiresistant E. coli samples are collected from swine with enterocolitis tested for resistance levels using the disc diffusimetric method (Kirby-Bauer disc diffusion). Pathogen identification completed using the API 20E multitest system revealed the E. coli presence in 11 samples. In these samples, bacterial membrane detection of fatty acid methyl esters (FAME) operating a 240 MS Ion Trap (Varian) GC/MS (Agilent Technologies, Santa Clara, CA, USA) was performed, using the MIDI Sherlock recognition software model.

Results

Interpreting the descriptive statistical method, the correlation matrix, and regression curves and after ANOVA analysis, we ascertained that the studied E. coli population statistically confirmed different degrees of resistance in most of the samples analyzed in this test.

Conclusions

In one case, the methyl-(Z)-11-tetradecenoate acid was observed to have a relationship with the susceptibility evaluation by using the disc diffusimetric method, which has revealed the lowest rate of antimicrobial resistance, so it has importance in further resistance evaluation studies.

Diverse Mechanisms of Antimicrobial Activities of Lactoferrins, Lactoferricins, and Other Lactoferrin-Derived Peptides

Lactoferrins are an iron-binding glycoprotein that have important protective roles in the mammalian body through their numerous functions, which include antimicrobial, antitumor, anti-inflammatory, immunomodulatory, and antioxidant activities. Among these, their antimicrobial activity has been the most studied, although the mechanism behind antimicrobial activities remains to be elucidated. Thirty years ago, the first lactoferrin-derived peptide was isolated and showed higher antimicrobial activity than the native lactoferrin lactoferricin. Since then, numerous studies have investigated the antimicrobial potencies of lactoferrins, lactoferricins, and other lactoferrin-derived peptides to better understand their antimicrobial activities at the molecular level. This review defines the current antibacterial, antiviral, antifungal, and antiparasitic activities of lactoferrins, lactoferricins, and lactoferrin-derived peptides. The primary focus is on their different mechanisms of activity against bacteria, viruses, fungi, and parasites. The role of their structure, amino-acid composition, conformation, charge, hydrophobicity, and other factors that affect their mechanisms of antimicrobial activity are also reviewed.