Optimizing the formulation of Erwinia bacteriophages for improved UV stability and adsorption on apple leaves

Characterizations of Newly Isolated Erwinia amylovora Loessnervirus-like Bacteriophages from Hungary

This study explores alternative methods to combat bacterial infections like fire blight caused by Erwinia amylovora (Ea) using bacteriophages as potential antimicrobial agents. Two lytic phages, Ea PF 7 and Ea PF 9, were isolated from apple samples and classified as Loessnervirus-like based on their genomes. Both phages showed strong efficacy, lysing 95% of the tested 37 Ea strains. They inhibited bacterial growth for up to 10 h, even at low infection rates. The phages had a short latent period of 10 min and produced high burst sizes of 108 and 125 phage particles per infected cell. Stability tests revealed that both phages were stable at moderate temperatures (37-45 °C) and within a pH range of 4-10. However, their viability decreased at higher temperatures and extreme pH levels. Both phages exhibited notable desiccation tolerance and moderate resistance to UV-B radiation during UV testing. The phages were exposed to carefully controlled irradiation, considering factors like lamp type, radiation intensity, exposure time, and object distance. This method introduces a complex approach to research, ensuring repeatable and comparable results. These findings suggest that Ea PF 7 and Ea PF 9 hold promise as antimicrobial agents for therapeutic and biotechnological applications, potentially helping to combat antibiotic resistance in the future.

Characterization of novel Erwinia amylovora-specific phiEaSP1 phage and its application as phage cocktail for managing fire blight in apples

Erwinia amylovora (Ea) is a devastating bacterial pathogen that causes fire blight disease in Rosaceae family plants, including apples and pears. The use of bacteriophages is an alternative strategy to antibiotics for managing bacterial pathogens. In this study, the Ea-specific virulent phiEaSP1 phage was characterized, and its biocontrol efficacy against Ea was evaluated in apple seedlings. Genomic analyses revealed that phiEaSP1 belongs to the family Chaseviridae, subfamily Cleopatravirinae, and genus Loessnervirus. Most phiEaSP1 particles bound to the host cell surface within 5 min, and one virion made 68 progenies within 20 min of infection. The phage rapidly lysed Ea cells in vitro and maintained its lytic activity after incubation under different environmental conditions, including temperature, pH, and UV-A, as well as in the soil, with surfactants, and on apple seedlings. Receptor analysis using the Tn5 random mutant library of Ea TS3128 demonstrated that phiEaSP1 recognizes lipopolysaccharide as a receptor, whereas phiEaP-8 and phiEaP-21 recognize cellulose as a receptor. Protective efficacy against fire blight was tested on apple seedlings pretreated with the single phiEaSP1 or a phage cocktail containing phiEaSP1, phiEaP-8, and phiEaP-21. No or only weak symptoms were observed in the phage-treated seedlings. The application of a phage cocktail showed better control efficacy, indicating the potential of the phage cocktail, including phiEaSP1, as a preventive agent. Taken together, these results suggest that the use of a phage cocktail containing phiEaSP1 could be a potential strategy for the biocontrol of fire blight disease in apples.

Application of phytosynthesized silver nanoparticles (SNPs) against Erwinia amylovora causing fire blight disease

The bacterium Erwinia amylovora is responsible for the destructive disease known as fire blight in pear trees. This highly detrimental condition poses a significant threat to the health and vitality of these trees. The existing strategies for managing fire blight disease involve the regular use of copper compounds and streptomycin, particularly during periods when environmental factors are conducive to the spread of the infection. Silver nanoparticles, also known as SNPs, are tiny specks of silver ranging in size from 10 to 100 nm. These particles are created through various chemical and biological processes. Numerous studies have demonstrated their ability to exhibit antibacterial properties against a wide range of human and animal pathogens. In this investigation, the dimensions of SNPs were ascertained by employing aqueous extracts derived from apple, pear, and quince leaves. The average sizes of the SNPs were found to be approximately 30 nm, 38 nm, and 55 nm, apple, quince and pear respectively. The pear mature fruits successfully managed to control the rot caused by the disease-causing E. amylovora. This study shows the viability of utilizing leaves extract from apple, pear, and quince as a suitable medium for the production of silver nanoparticles. These nanoparticles hold potential for effectively managing fire blight disease.

Advancements in Bacteriophages for the Fire Blight Pathogen Erwinia amylovora

Erwinia amylovora, the causative agent of fire blight, causes significant economic losses for farmers worldwide by inflicting severe damage to the production and quality of plants in the Rosaceae family. Historically, fire blight control has primarily relied on the application of copper compounds and antibiotics, such as streptomycin. However, the emergence of antibiotic-resistant strains and growing environmental concerns have highlighted the need for alternative control methods. Recently, there has been a growing interest in adopting bacteriophages (phages) as a biological control strategy. Phages have demonstrated efficacy against the bacterial plant pathogen E. amylovora, including strains that have developed antibiotic resistance. The advantages of phage therapy includes its minimal impact on microbial community equilibrium, the lack of a detrimental impact on plants and beneficial microorganisms, and its capacity to eradicate drug-resistant bacteria. This review addresses recent advances in the isolation and characterization of E. amylovora phages, including their morphology, host range, lysis exertion, genomic characterization, and lysis mechanisms. Furthermore, this review evaluates the environmental tolerance of E. amylovora phages. Despite their potential, E. amylovora phages face certain challenges in practical applications, including stability issues and the risk of lysogenic conversion. This comprehensive review examines the latest developments in the application of phages for controlling fire blight and highlights the potential of E. amylovora phages in plant protection strategies.

Evaluation of Different Formulations on the Viability of Phages for Use in Agriculture

Bacteriophages have been proposed as biological controllers to protect plants against different bacterial pathogens. In this scenario, one of the main challenges is the low viability of phages in plants and under adverse environmental conditions. This work explores the use of 12 compounds and 14 different formulations to increase the viability of a phage mixture that demonstrated biocontrol capacity against Pseudomonas syringae pv. actinidiae (Psa) in kiwi plants. The results showed that the viability of the phage mixture decreases at 44 °C, at a pH lower than 4, and under UV radiation. However, using excipients such as skim milk, casein, and glutamic acid can prevent the viability loss of the phages under these conditions. Likewise, it was demonstrated that the use of these compounds prolongs the presence of phages in kiwi plants from 48 h to at least 96 h. In addition, it was observed that phages remained stable for seven weeks when stored in powder with skim milk, casein, or sucrose after lyophilization and at 4 °C. Finally, the phages with glutamic acid, sucrose, or skim milk maintained their antimicrobial activity against Psa on kiwi leaves and persisted within kiwi plants when added through roots. This study contributes to overcoming the challenges associated with the use of phages as biological controllers in agriculture.

Exploring the historical roots, advantages and efficacy of phage therapy in plant diseases management

In the drug-resistance era, phage therapy has received considerable attention from worldwide researchers. Phage therapy has been given much attention in public health but is rarely applied to control plant diseases. Herein, we discuss phage therapy as a biocontrol approach against several plant diseases. The emergence of antibiotic resistance in agriculturally important pathogenic bacteria and the toxic nature of different synthetic compounds used to control microbes has driven researchers to rethink the century-old strategy of phage therapy''. Compared to other treatment strategies, phage therapy offers remarkable advantages such as high specificity, less chances of drug resistance, non-harmful nature, and benefit to soil microbial flora. The optimizations and protective formulations of phages are significant accomplishments; however, steps towards a better understanding of the physiologic characteristics of phages need to be preceded to commercialize their use. The future of phage therapy in the context of plant disease management is promising and could play a significant role in sustainable agriculture. Ongoing research will likely affirm the safety of phage therapy, ensuring that it does not harm non-target organisms, including beneficial soil microbes. Phage therapy could become vital in addressing global food security challenges, particularly in regions heavily impacted by plant bacterial diseases. Efforts to create formulations that enhance the stability and shelf-life of phages will be crucial, especially for their use in varied environmental conditions.