Prediction and Characterization of Cationic Arginine-Rich Plant Antimicrobial Peptide SM-985 From Teosinte (Zea mays ssp. mexicana)

BsR1, a broad-spectrum antibacterial peptide with potential for plant protection

IMPORTANCE

This study addresses the critical need for new antibacterial drugs in the face of bacterial multidrug resistance resulting from antibiotic overuse. It highlights the significance of antimicrobial peptides as essential components of innate immunity in animals and plants, which have been proven effective against multidrug-resistant bacteria and are difficult to develop resistance against. This study successfully synthesizes a broad-spectrum antibacterial peptide, BsR1, with strong inhibitory activities against various Gram-positive and Gram-negative bacteria. BsR1 demonstrates favorable stability and a mode of action that damages bacterial cell membranes, leading to cell death. It also exhibits biological safety and shows potential in enhancing disease resistance in rice. This research offers a novel approach and potential medication for antibacterial drug development, presenting a valuable tool in combating pathogenic microorganisms, particularly in plants.

A peptide encoded by a highly conserved gene belonging to the genus Streptomyces shows antimicrobial activity against plant pathogens

The genus Streptomyces has been unceasingly highlighted for the versatility and diversity of the antimicrobial agents they produce. Moreover, it is a heavily sequenced taxon in the phylum Actinobacteria. In this study, 47 sequence profiles were identified as proteins highly conserved within the genus Streptomyces. Significant hits to the 38 profiles were found in more than 2000 Streptomyces genomes, 11 of which were further conserved in more than 90% of Actinobacterial genomes analyzed. Only a few genes corresponding to these sequence profiles were functionally characterized, which play regulatory roles in the morphology and biosynthesis of antibiotics. Here a highly conserved sequence, namely, SHC-AMP (Streptomyces highly conserved antimicrobial peptide), which exhibited antimicrobial activity against bacterial and fungal plant pathogens, was reported. In particular, Arabidopsis thaliana was effectively protected against infection with Pseudomonas syringae pv. tomato DC3000 by treatment with this peptide. Results indicated the potential application of this peptide as an antimicrobial agent for control of plant diseases. Our results suggest putative target genes for controlling Streptomyces spp., including the one exhibiting antimicrobial activity against a wide range of phytopathogens.

Antibacterial activities of coumarin-3-carboxylic acid against Acidovorax citrulli

Coumarin-3-carboxylic acid (3-CCA), previously screened from natural coumarins, was found to possess strong antibacterial activity against Acidovorax citrulli (Ac). In order to further evaluate the activity of this compound against plant bacterial pathogens and explore its potential value as a bactericidal lead compound, the activity of 3-CCA against 14 plant pathogenic bacteria in vitro and in vivo was tested. Results showed that 3-CCA exhibited strong in vitro activities against Ac, Ralstonia solanacearum, Xanthomonas axonopodis pv. manihotis, X. oryzae pv. oryzae, and Dickeya zeae with EC50 values ranging from 26.64 μg/mL to 40.73 μg/mL. Pot experiment results showed that 3-CCA had powerful protective and curative effects against Ac. In addition, the protective efficiency of 3-CCA was almost equivalent to that of thiodiazole copper at the same concentration. The results of SEM and TEM observation and conductivity tests showed that 3-CCA disrupted the integrity of the cell membrane and inhibited polar flagella growth. Furthermore, 3-CCA resulted in reductions in motility and extracellular exopolysaccharide (EPS) production of Ac while inhibiting the biofilm formation of Ac. These findings indicate that 3-CCA could be a promising natural lead compound against plant bacterial pathogens to explore novel antibacterial agents.

Identification, Screening and Antibacterial Mechanism Analysis of Novel Antimicrobial Peptides from Sturgeon (Acipenser ruthenus) Spermary

Fish is an important source of antimicrobial peptides. This study aimed to identify and screen antibacterial peptides with excellent antibacterial activity derived from sturgeon spermary peptides (SSPs) and to analyze their antibacterial activity and mechanism. Liquid chromatography-mass spectrometry/mass spectrometry methods were used to analyze and identify peptide sequences, computational prediction tool and molecular docking methods were used for virtual screening of antimicrobial peptides, and finally, candidate peptides were synthesized by solid-phase synthesis method. The results demonstrate that SSPs have excellent inhibitory activity against Escherichia coli with an inhibitory rate of 76.46%. Most parts of the SSPs were derived from the sturgeon (Acipenser ruthenus) histones, and the coverage of histone H2B was the highest (45%). Two novel peptides (NDEELNKLM and RSSKRRQ) were obtained by in silico prediction tools and molecular docking, which may interact with the DNA gyrase and dihydrofolate reductase of E. coli by forming salt bridges and hydrogen bonds. Compared to the individual peptides, the antibacterial effect was significantly improved by mixing the two peptides in equal proportions. Two novel peptides change the permeability of the E. coli cell membranes and may exert antimicrobial activity by inhibiting the metabolic process of the nucleic acids.

Evaluation of Three Antimicrobial Peptides Mixtures to Control the Phytopathogen Responsible for Fire Blight Disease

Fire blight is a severe bacterial plant disease that affects important chain-of-value fruit trees such as pear and apple trees. This disease is caused by Erwinia amylovora, a quarantine phytopathogenic bacterium, which, although highly distributed worldwide, still lacks efficient control measures. The green revolution paradigm demands sustainable agriculture practices, for which antimicrobial peptides (AMPs) have recently caught much attention. The goal of this work was to disclose the bioactivity of three peptides mixtures (BP100:RW-BP100, BP100:CA-M, and RW-BP100:CA-M), against three strains of E. amylovora representing distinct genotypes and virulence (LMG 2024, Ea 630 and Ea 680). The three AMPs' mixtures were assayed at eight different equimolar concentrations ranging from 0.25 to 6 μM (1:1). Results showed MIC and MBC values between 2.5 and 4 μM for every AMP mixture and strain. Regarding cell viability, flow cytometry and alamarBlue reduction, showed high reduction (>25%) of viable cells after 30 min of AMP exposure, depending on the peptide mixture and strain assayed. Hypersensitive response in tobacco plants showed that the most efficient AMPs mixtures and concentrations caused low to no reaction of the plant. Altogether, the AMPs mixtures studied are better treatment solutions to control fire blight disease than the same AMPs applied individually.

Antimicrobial Peptides from Plants: A cDNA-Library Based Isolation, Purification, Characterization Approach and Elucidating Their Modes of Action

Even in a natural ecosystem, plants are continuously threatened by various microbial diseases. To save themselves from these diverse infections, plants build a robust, multilayered immune system through their natural chemical compounds. Among the several crucial bioactive compounds possessed by plants’ immune systems, antimicrobial peptides (AMPs) rank in the first tier. These AMPs are environmentally friendly, anti-pathogenic, and do not bring harm to humans. Antimicrobial peptides can be isolated in several ways, but recombinant protein production has become increasingly popular in recent years, with the Escherichia coli expression system being the most widely used. However, the efficacy of this expression system is compromised due to the difficulty of removing endotoxin from its system. Therefore, this review suggests a high-throughput cDNA library-based plant-derived AMP isolation technique using the Bacillus subtilis expression system. This method can be performed for large-scale screening of plant sources to classify unique or homologous AMPs for the agronomic and applied field of plant studies. Furthermore, this review also focuses on the efficacy of plant AMPs, which are dependent on their numerous modes of action and exceptional structural stability to function against a wide range of invaders. To conclude, the findings from this study will be useful in investigating how novel AMPs are distributed among plants and provide detailed guidelines for an effective screening strategy of AMPs.

Prediction and Activity of a Cationic α-Helix Antimicrobial Peptide ZM-804 from Maize

Antimicrobial peptides (AMPs) are small molecules consisting of less than fifty residues of amino acids. Plant AMPs establish the first barrier of defense in the innate immune system in response to invading pathogens. The purpose of this study was to isolate new AMPs from the Zea mays L. inbred line B73 and investigate their antimicrobial activities and mechanisms against certain essential plant pathogenic bacteria. In silico, the Collection of Anti-Microbial Peptides (CAMP_R3), a computational AMP prediction server, was used to screen a cDNA library for AMPs. A ZM-804 peptide, isolated from the Z. mays L. inbred line B73 cDNA library, was predicted as a new cationic AMP with high prediction values. ZM-804 was tested against eleven pathogens of Gram-negative and Gram-positive bacteria and exhibited high antimicrobial activities as determined by the minimal inhibitory concentrations (MICs) and the minimum bactericidal concentrations (MBCs). A confocal laser scanning microscope observation showed that the ZM-804 AMP targets bacterial cell membranes. SEM and TEM images revealed the disruption and damage of the cell membrane morphology of Clavibacter michiganensis subsp. michiganensis and Pseudomonas syringae pv. tomato (Pst) DC3000 caused by ZM-804. In planta, ZM-804 demonstrated antimicrobial activity and prevented the infection of tomato plants by Pst DC3000. Moreover, four virulent phytopathogenic bacteria were prevented from inducing hypersensitive response (HR) in tobacco leaves in response to low ZM-804 concentrations. ZM-804 exhibits low hemolytic activity against mouse red blood cells (RBCs) and is relatively safe for mammalian cells. In conclusion, the ZM-804 peptide has a strong antibacterial activity and provides an alternative tool for plant disease control. Additionally, the ZM-804 peptide is considered a promising candidate for human and animal drug development.

Identification of a Novel Cathelicidin from the Deinagkistrodon acutus Genome with Antibacterial Activity by Multiple Mechanisms

The abuse of antibiotics and the consequent increase of drug-resistant bacteria constitute a serious threat to human health, and new antibiotics are urgently needed. Research shows that antimicrobial peptides produced by natural organisms are potential substitutes for antibiotics. Based on Deinagkistrodonacutus (known as five-pacer viper) genome bioinformatics analysis, we discovered a new cathelicidin antibacterial peptide which was called FP-CATH. Circular dichromatic analysis showed a typical helical structure. FP-CATH showed broad-spectrum antibacterial activity. It has antibacterial activity to Gram-negative bacteria and Gram-positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA). The results of transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed that FP-CATH could cause the change of bacterial cell integrity, having a destructive effect on Gram-negative bacteria and inducing Gram-positive bacterial surface formation of vesicular structure. FP-CATH could bind to LPS and showed strong binding ability to bacterial DNA. In vivo, FP-CATH can improve the survival rate of nematodes in bacterial invasion experiments, and has a certain protective effect on nematodes. To sum up, FP-CATH is likely to play a role in multiple mechanisms of antibacterial action by impacting bacterial cell integrity and binding to bacterial biomolecules. It is hoped that the study of FP-CATH antibacterial mechanisms will prove useful for development of novel antibiotics.

Isolation of Antimicrobial Genes from Oryza rufipogon Griff by Using a Bacillus subtilis Expression System with Potential Antimicrobial Activities

Antimicrobial genes are distributed in all forms of life and provide a primary defensive shield due to their unique broad-spectrum resistance activities. To better isolate these genes, we used the Bacillus subtilis expression system as the host cells to build Oryza rufipogon Griff cDNA libraries and screen potential candidate genes from the library at higher flux using built-in indicator bacteria. We observed that the antimicrobial peptides OrR214 and OrR935 have strong antimicrobial activity against a variety of Gram-positive and Gram-negative bacteria, as well as several fungal pathogens. Owing to their high thermal and enzymatic stabilities, these two peptides can also be used as field biocontrol agents. Furthermore, we also found that the peptide OrR214 (MIC 7.7-10.7 μM) can strongly inhibit bacterial growth compared to polymyxin B (MIC 5-25 μM) and OrR935 (MIC 33-44 μM). The cell flow analysis, reactive oxygen burst, and electron microscopy (scanning and transmission electron microscopy) observations showed that the cell membranes were targeted by peptides OrR214 and OrR935, which revealed the mode of action of bacteriostasis. Moreover, the hemolytic activity, toxicity, and salt sensitivity experiments demonstrated that these two peptides might have the potential to be used for clinical applications. Overall, OrR214 and OrR935 antimicrobial peptides have a high-throughput bacteriostatic activity that acts as a new form of antimicrobial agent and can be used as a raw material in the field of drug development.