Phage cocktail containing Podoviridae and Myoviridae bacteriophages inhibits the growth of Pectobacterium spp. under in vitro and in vivo conditions

Pangenomics to understand prophage dynamics in the Pectobacterium genus and the radiating lineages of Pectobacterium brasiliense

Bacterial pathogens of the genus Pectobacterium are responsible for soft-rot and blackleg diseases in a wide range of crops and have a global impact on food production. The emergence of new lineages and their competitive succession is frequently observed in Pectobacterium species, in particular in Pectobacterium brasiliense. With a focus on one such recently emerged P. brasiliense lineage in the Netherlands that causes blackleg in potatoes, we studied genome evolution in this genus using a reference-free graph-based pangenome approach. We clustered 1,977,865 proteins from 454 Pectobacterium spp. genomes into 30,156 homology groups. The Pectobacterium genus pangenome is open, and its growth is mainly contributed by the accessory genome. Bacteriophage genes were enriched in the accessory genome and contributed 16% of the pangenome. Blackleg-causing P. brasiliense isolates had increased genome size with high levels of prophage integration. To study the diversity and dynamics of these prophages across the pangenome, we developed an approach to trace prophages across genomes using pangenome homology group signatures. We identified lineage-specific as well as generalist bacteriophages infecting Pectobacterium species. Our results capture the ongoing dynamics of mobile genetic elements, even in the clonal lineages. The observed lineage-specific prophage dynamics provide mechanistic insights into Pectobacterium pangenome growth and contribution to the radiating lineages of P. brasiliense.

Lytic Spectra of Tailed Bacteriophages: A Systematic Review and Meta-Analysis

As natural predators of bacteria, tailed bacteriophages can be used in biocontrol applications, including antimicrobial therapy. Also, phage lysis is a detrimental factor in technological processes based on bacterial growth and metabolism. The spectrum of bacteria bacteriophages interact with is known as the host range. Phage science produced a vast amount of host range data. However, there has been no attempt to analyse these data from the viewpoint of modern phage and bacterial taxonomy. Here, we performed a meta-analysis of spotting and plaquing host range data obtained on strains of production host species. The main metric of our study was the host range value calculated as a ratio of lysed strains to the number of tested bacterial strains. We found no boundary between narrow and broad host ranges in tailed phages taken as a whole. Family-level groups of strictly lytic bacteriophages had significantly different median plaquing host range values in the range from 0.18 (Drexlerviridae) to 0.70 (Herelleviridae). In Escherichia coli phages, broad host ranges were associated with decreased efficiency of plating. Bacteriophage morphology, genome size, and the number of tRNA-coding genes in phage genomes did not correlate with host range values. From the perspective of bacterial species, median plaquing host ranges varied from 0.04 in bacteriophages infecting Acinetobacter baumannii to 0.73 in Staphylococcus aureus phages. Taken together, our results imply that taxonomy of bacteriophages and their bacterial hosts can be predictive of intraspecies host ranges.

Bacteriophage cocktail for biocontrol of soft rot disease caused by Pectobacterium species in Chinese cabbage

Pectobacterium spp. are necrotrophic plant pathogens that cause the soft rot disease in Chinese cabbage, resulting in severe yield loss. The use of conventional antimicrobial agents, copper-based bactericides, and antibiotics has encountered several limitations, such as bioaccumulation on plants and microbial resistance. Bacteriophages (phages) are considered promising alternative antimicrobial agents against diverse phytopathogens. In this study, we isolated and characterized two virulent phages (phiPccP-2 and phiPccP-3) to develop a phage cocktail. Morphological and genomic analyses revealed that two phages belonged to the Tevenvirinae and Mccorquodalevirinae subfamilies, respectively. The phiPccP-2 and phiPccP-3 phages, which have a broad host range, were stable at various environmental conditions, such as various pHs and temperatures and exposure to ultraviolet light. The phage cocktail developed using these two lytic phages inhibited the emergence of phage-resistant bacteria compared to single-phage treatments in in vitro challenge assays. The phage cocktail treatment effectively prevented the development of soft rot symptom in matured Chinese cabbage leaves. Additionally, the phage cocktail comprising three phages (phiPccP-1, phiPccP-2, and phiPccP-3) showed superior biocontrol efficacy against the mixture of Pectobacterium strains in Chinese cabbage seedlings. These results suggest that developing phage cocktails is an effective approach for biocontrol of soft rot disease caused by Pectobacterium strains in crops compared to single-phage treatments. KEY POINTS: •Two newly isolated Pectobacterium phages, phiPccP-2 and phiPccP-3, infected diverse Pectobacterium species and effectively inhibited the emergence of phage-resistant bacteria. •Genomic and physiological analyses suggested that both phiPccP-2 and phiPccP-3 are lytic phages and that their lytic activities are stable in the environmental conditions under which Chinese cabbage grows. •Treatment using a phage cocktail comprising phiPccP-2 and phiPccP-3 efficiently suppressed soft rot disease in detached mature leaves and seedlings of Chinese cabbage, indicating the applicability of the phage cocktail as an alternative antimicrobial agent.

Bacteriophage-mediated approaches for biofilm control

Biofilms are complex microbial communities in which planktonic and dormant bacteria are enveloped in extracellular polymeric substances (EPS) such as exopolysaccharides, proteins, lipids, and DNA. These multicellular structures present resistance to conventional antimicrobial treatments, including antibiotics. The formation of biofilms raises considerable concern in healthcare settings, biofilms can exacerbate infections in patients and compromise the integrity of medical devices employed during treatment. Similarly, certain bacterial species contribute to bulking, foaming, and biofilm development in water environments such as wastewater treatment plants, water reservoirs, and aquaculture facilities. Additionally, food production facilities provide ideal conditions for establishing bacterial biofilms, which can serve as reservoirs for foodborne pathogens. Efforts to combat antibiotic resistance involve exploring various strategies, including bacteriophage therapy. Research has been conducted on the effects of phages and their individual proteins to assess their potential for biofilm removal. However, challenges persist, prompting the examination of refined approaches such as drug-phage combination therapies, phage cocktails, and genetically modified phages for clinical applications. This review aims to highlight the progress regarding bacteriophage-based approaches for biofilm eradication in different settings.

A novel genus of Pectobacterium bacteriophages display broad host range by targeting several species of Danish soft rot isolates

The bacterial diseases black leg and soft rot in potatoes cause heavy losses of potatoes worldwide. Bacteria within the genus Pectobacteriaceae are the causative agents of black leg and soft rot. The use of antibiotics in agriculture is heavily regulated and no other effective treatment currently exists, but bacteriophages (phages) have shown promise as potential biocontrol agents. In this study we isolated soft rot bacteria from potato tubers and plant tissue displaying soft rot or black leg symptoms collected in Danish fields. We then used the isolated bacterial strains as hosts for phage isolation. Using organic waste, we isolated phages targeting different species within Pectobacterium. Here we focus on seven of these phages representing a new genus primarily targeting P. brasiliense; phage Ymer, Amona, Sabo, Abuela, Koroua, Taid and Pappous. TEM image of phage Ymer showed siphovirus morphotype, and the proposed Ymer genus belongs to the class Caudoviricetes, with double-stranded DNA genomes varying from 39 kb to 43 kb. In silico host range prediction using a CRISPR-Cas spacer database suggested both P. brasiliense, P. polaris and P. versatile as natural hosts for phages within the proposed Ymer genus. A following host range experiment, using 47 bacterial isolates from Danish tubers and plants symptomatic with soft rot or black leg disease verified the in silico host range prediction, as the genus as a group were able to infect all three Pectobacterium species. Phages did, however, primarily target P. brasiliense isolates and displayed differences in host range even within the species level. Two of the phages were able to infect two or more Pectobacterium species. Despite no nucleotide similarity with any phages in the NCBI database, the proposed Ymer genus did share some similarity at the protein level, as well as gene synteny, with currently known phages. None of the phages encoded integrases or other genes typically associated with lysogeny. Similarly, no virulence factors nor antimicrobial resistance genes were found, and combined with their ability to infect several soft rot-causing Pectobacterium species from Danish fields, demonstrates their potential as biocontrol agents against soft rot and black leg diseases in potatoes.

Isolation and Biological Characteristics of a Novel Phage and Its Application to Control Vibrio Parahaemolyticus in Shellfish Meat

Vibrio parahaemolyticus is a common foodborne pathogenic bacterium. With the overuse of antibiotics, an increasing proportion of drug-resistant strains are emerging, which puts enormous pressure on public health. In this study, a V. parahaemolyticus-specific phage, VP41s3, was isolated. The head length, width, and tail length of the phage were 77.7 nm, 72.2 nm, and 17.5 nm, respectively. It remained active in the temperature range of 30-50°C and pH range of 4-11. The lytic curve of phage VP41s3 showed that the host bacteria did not grow until 11 h under phage treatment at MOI of 1000, indicating that the phage had good bacteriostatic ability. When it was added to shellfish contaminated with V. parahaemolyticus (15°C, 48 h), the number of bacteria in the experimental group was 2.11 log10 CFU/mL lower than that in the control group at 24 h. Furthermore, genomic characterization and phylogenetic analysis indicated that phage VP41s3 was a new member of the Podoviridae family. The genome contained 50 open reading frames (ORFs), in which the ORF19 (thymidine kinase) was an enzyme involved in the pyrimidine salvage pathway, which might lead to the accelerated DNA synthesis efficiency after phage entered into host cells. This study not only contributed to the improvement of phage database and the development of beneficial phage resources but also revealed the potential application of phage VP41s3 in food hygiene and safety.

Antibiotic Resistance in Plant Pathogenic Bacteria: Recent Data and Environmental Impact of Unchecked Use and the Potential of Biocontrol Agents as an Eco-Friendly Alternative

The economic impact of phytopathogenic bacteria on agriculture is staggering, costing billions of US dollars globally. Pseudomonas syringae is the top most phytopathogenic bacteria, having more than 60 pathovars, which cause bacteria speck in tomatoes, halo blight in beans, and so on. Although antibiotics or a combination of antibiotics are used to manage infectious diseases in plants, they are employed far less in agriculture compared to human and animal populations. Moreover, the majority of antibiotics used in plants are immediately washed away, leading to environmental damage to ecosystems and food chains. Due to the serious risk of antibiotic resistance (AR) and the potential for environmental contamination with antibiotic residues and resistance genes, the use of unchecked antibiotics against phytopathogenic bacteria is not advisable. Despite the significant concern regarding AR in the world today, there are inadequate and outdated data on the AR of phytopathogenic bacteria. This review presents recent AR data on plant pathogenic bacteria (PPB), along with their environmental impact. In light of these findings, we suggest the use of biocontrol agents as a sustainable, eco-friendly, and effective alternative to controlling phytopathogenic bacteria.

Unique trans-kingdom microbiome structural and functional signatures predict cognitive decline in older adults

The prevalence of age-related cognitive disorders/dementia is increasing, and effective prevention and treatment interventions are lacking due to an incomplete understanding of aging neuropathophysiology. Emerging evidence suggests that abnormalities in gut microbiome are linked with age-related cognitive decline and getting acceptance as one of the pillars of the Geroscience hypothesis. However, the potential clinical importance of gut microbiome abnormalities in predicting the risk of cognitive decline in older adults is unclear. Till now the majority of clinical studies were done using 16S rRNA sequencing which only accounts for analyzing bacterial abundance, while lacking an understanding of other crucial microbial kingdoms, such as viruses, fungi, archaea, and the functional profiling of the microbiome community. Utilizing data and samples of older adults with mild cognitive impairment (MCI; n = 23) and cognitively healthy controls (n = 25). Our whole-genome metagenomic sequencing revealed that the gut of older adults with MCI harbors a less diverse microbiome with a specific increase in total viruses and a decrease in bacterial abundance compared with controls. The virome, bacteriome, and microbial metabolic signatures were significantly distinct in subjects with MCI versus controls. Selected bacteriome signatures show high predictive potential of cognitive dysfunction than virome signatures while combining virome and metabolic signatures with bacteriome boosts the prediction power. Altogether, the results from our pilot study indicate that trans-kingdom microbiome signatures are significantly distinct in MCI gut compared with controls and may have utility for predicting the risk of developing cognitive decline and dementia- debilitating public health problems in older adults.

The Safety of Bacteriophages in Treatment of Diseases Caused by Multidrug-Resistant Bacteria

Given the urgency due to the rapid emergence of multidrug-resistant (MDR) bacteria, bacteriophages (phages), which are viruses that specifically target and kill bacteria, are rising as a potential alternative to antibiotics. In recent years, researchers have begun to elucidate the safety aspects of phage therapy with the aim of ensuring safe and effective clinical applications. While phage therapy has generally been demonstrated to be safe and tolerable among animals and humans, the current research on phage safety monitoring lacks sufficient and consistent data. This emphasizes the critical need for a standardized phage safety assessment to ensure a more reliable evaluation of its safety profile. Therefore, this review aims to bridge the knowledge gap concerning phage safety for treating MDR bacterial infections by covering various aspects involving phage applications, including phage preparation, administration, and the implications for human health and the environment.

Complete genome analysis of Tequatrovirus ufvareg1, a Tequatrovirus species inhibiting Escherichia coli O157:H7

Introduction

Bacteriophages infecting human pathogens have been considered potential biocontrol agents, and studying their genetic content is essential to their safe use in the food industry. Tequatrovirus ufvareg1 is a bacteriophage named UFV-AREG1, isolated from cowshed wastewater and previously tested for its ability to inhibit Escherichia coli O157:H7.

Methods

T. ufvareg1 was previously isolated using E. coli O157:H7 (ATCC 43895) as a bacterial host. The same strain was used for bacteriophage propagation and the one-step growth curve. The genome of the T. ufvareg1 was sequenced using 305 Illumina HiSeq, and the genome comparison was calculated by VIRIDIC and VIPTree.

Results

Here, we characterize its genome and compare it to other Tequatrovirus. T. ufvareg1 virions have an icosahedral head (114 x 86 nm) and a contracted tail (117 x 23 nm), with a latent period of 25 min, and an average burst size was 18 phage particles per infected E. coli cell. The genome of the bacteriophage T. ufvareg1 contains 268 coding DNA sequences (CDS) and ten tRNA genes distributed in both negative and positive strains. T. ufvareg1 genome also contains 40 promoters on its regulatory regions and two rho-independent terminators. T. ufvareg1 shares an average intergenomic similarity (VIRIDC) of 88.77% and an average genomic similarity score (VipTree) of 88.91% with eight four reference genomes for Tequatrovirus available in the NCBI RefSeq database. The pan-genomic analysis confirmed the high conservation of Tequatrovirus genomes. Among all CDS annotated in the T. ufvareg1 genome, there are 123 core genes, 38 softcore genes, 94 shell genes, and 13 cloud genes. None of 268 CDS was classified as being exclusive of T. ufvareg1.

Conclusion

The results in this paper, combined with other previously published findings, indicate that T. ufvareg1 bacteriophage is a potential candidate for food protection against E. coli O157:H7 in foods.

Current trends in management of bacterial pathogens infecting plants

Plants are continuously challenged by different pathogenic microbes that reduce the quality and quantity of produce and therefore pose a serious threat to food security. Among them bacterial pathogens are known to cause disease outbreaks with devastating economic losses in temperate, tropical and subtropical regions throughout the world. Bacteria are structurally simple prokaryotic microorganisms and are diverse from a metabolic standpoint. Bacterial infection process mainly involves successful attachment or penetration by using extracellular enzymes, type secretion systems, toxins, growth regulators and by exploiting different molecules that modulate plant defence resulting in successful colonization. Theses bacterial pathogens are extremely difficult to control as they develop resistance to antibiotics. Therefore, attempts are made to search for innovative methods of disease management by the targeting bacterial virulence and manipulating the genes in host plants by exploiting genome editing methods. Here, we review the recent developments in bacterial disease management including the bioactive antimicrobial compounds, bacteriophage therapy, quorum-quenching mediated control, nanoparticles and CRISPR/Cas based genome editing techniques for bacterial disease management. Future research should focus on implementation of smart delivery systems and consumer acceptance of these innovative methods for sustainable disease management.

Isolation of bacteriophages infecting Xanthomonas oryzae pv. oryzae and genomic characterization of novel phage vB_XooS_NR08 for biocontrol of bacterial leaf blight of rice

Bacterial leaf blight (BLB) disease of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most destructive diseases worldwide in rice-growing regions. The Ineffectiveness of chemicals in disease management has increased the interest in phage therapy. In this study, we isolated 19 bacteriophages, infecting Xoo, from a rice field, which belonged to phage families Siphoviridae, Myoviridae, and Podoviridae on the basis of electron microscopy. Among 19 phages, Phage vB_XooS_NR08, a member of the Siphoviridae family, expressed antibacterial activity against all Xoo strains tested and did not lyse X. campestris and other unrelated bacterial hosts. Phage NR08 showed more than 80% viability at a temperature range of 4°C–40°C, pH range of 5–9, and direct exposure to sunlight for 2 h, whereas UV light and chemical agents were highly detrimental. In a one-step growth curve, NR08 has a 40-min latent period, followed by a 30-min burst period with a burst size of 250 particle/bacterium. The genome of NR08 is double-stranded DNA, linear having a size of 98,812 bp with a G + C content of 52.9%. Annotation of the whole-genome sequence indicated that NR08 encodes 142 putative open reading frames (ORFs), including one ORF for tRNA, namely, trna1-GlnTTG. Comparative genome analysis of NR08 showed that it shares maximum similarity with Pseudomonas phage PaMx42 (40% query coverage, 95.39% identity, and acc. Length 43,225) and Xanthomonas phage Samson (40% query coverage, 96.68% identity, and acc. Length 43,314). The average alignment percentage (AP) of NR08 with other Xoophages was only 0.32 to 1.25 since the genome of NR08 (98.8 kb) is almost double of most of the previously reported Xoophages (43–47 kb), thus indicating NR08 a novel Xoophage. In in vitro bacterial challenge assay, NR08 showed bacteriostasis up to 24 h and a 99.95% reduction in bacterial growth in 48 h. In rice pot efficacy trials, single-dose treatment of NR08 showed a significant reduction in disease up to 90.23% and 79.27% on 7 and 21 dpi, respectively. However, treatment using 2% skim milk-supplemented phage preparation was significantly less effective as compared to the neat phage preparation. In summary, this study characterized a novel Xoophage having the potential as a biocontrol agent in the mitigation of BLB in rice.

Bacteriophages as a Strategy to Protect Potato Tubers against Dickeya dianthicola and Pectobacterium carotovorum Soft Rot

The protective effect of bacteriophage suspensions (Ds3CZ + Ds20CZ and PcCB7V + PcCB251) on phytopathogenic bacteria causing soft rot of potato tubers, namely Dickeya dianthicola (D50, D200) and Pectobacterium carotovorum (P87, P224), was observed in ex vivo and in vitro experiments. Ex vivo tests were performed (with air access) on potato slices, on cylindrical cuts from the center of the tubers, and directly in whole potato tubers. In vitro experiments were carried out in a liquid medium using RTS-8 bioreactors, where bacterial growth was monitored as optical density. In particular, the inhibitory effects of phages were confirmed in experiments on potato slices, where suppression of rot development was evident at first glance. Phage treatment against selected bacteria positively affected potato hardness. Hardness of samples treated with bacteria only was statistically significantly reduced (p < 0.05 for D50 and p < 0.001 for D200 and P87). Ex vivo experiments confirmed significant inhibition of P87 symptom development, partial inhibition of D200 and D50 in phage-treated tubers, and no effect was observed for P224. The inhibitory effect of phages against bacteria was not observed in the in vitro experiment.

Development of a Bacteriophage Cocktail against Pectobacterium carotovorum Subsp. carotovorum and Its Effects on Pectobacterium Virulence

Pectobacterium carotovorum subsp. carotovorum is a necrotrophic plant pathogen that secretes plant cell wall-degrading enzymes (PCWDEs) that cause soft rot disease in various crops. Bacteriophages have been under consideration as harmless antibacterial agents to replace antibiotics and copper-based pesticides. However, the emergence of bacteriophage resistance is one of the main concerns that should be resolved for practical phage applications. In this study, we developed a phage cocktail with three lytic phages that recognize colanic acid (phage POP12) or flagella (phages POP15 and POP17) as phage receptors to minimize phage resistance. The phage cocktail effectively suppressed the emergence of phage-resistant P. carotovorum subsp. carotovorum compared with single phages in in vitro challenge assays. The application of the phage cocktail to napa cabbage (Brassica rapa subsp. pekinensis) resulted in significant growth retardation of P. carotovorum subsp. carotovorum (P < 0.05) and prevented the symptoms of soft rot disease. Furthermore, phage cocktail treatments of young napa cabbage leaves in a greenhouse environment indicated effective prevention of soft rot disease compared to that in the nonphage negative control. We isolated 15 phage-resistant mutants after a phage cocktail treatment to assess the virulence-associated phenotypes compared to those of wild-type (WT) strain Pcc27. All mutants showed reduced production of four different PCWDEs, leading to lower levels of tissue softening. Ten of the 15 phage-resistant mutants additionally exhibited decreased swimming motility. Taken together, these results show that the phage cocktail developed here, which targets two different types of phage receptors, provides an effective strategy for controlling P. carotovorum subsp. carotovorum in agricultural products, with a potential ability to attenuate P. carotovorum subsp. carotovorum virulence. IMPORTANCE Pectobacterium carotovorum subsp. carotovorum is a phytopathogen that causes soft rot disease in various crops by producing plant cell wall-degrading enzymes (PCWDEs). Although antibiotics and copper-based pesticides have been extensively applied to inhibit P. carotovorum subsp. carotovorum, the emergence of antibiotic-resistant bacteria and demand for harmless antimicrobial products have emphasized the necessity of finding alternative therapeutic strategies. To address this problem, we developed a phage cocktail consisting of three P. carotovorum subsp. carotovorum-specific phages that recognize colanic acids and flagella of P. carotovorum subsp. carotovorum. The phage cocktail treatments significantly decreased P. carotovorum subsp. carotovorum populations, as well as soft rot symptoms in napa cabbage. Simultaneously, they resulted in virulence attenuation in phage-resistant P. carotovorum subsp. carotovorum, which was represented by decreased PCWDE production and decreased flagellum-mediated swimming motility. These results suggested that preparations of phage cocktails targeting multiple receptors would be an effective approach to biocontrol of P. carotovorum subsp. carotovorum in crops.

Pectobacterium versatile Bacteriophage Possum: A Complex Polysaccharide-Deacetylating Tail Fiber as a Tool for Host Recognition in Pectobacterial Schitoviridae

Novel, closely related phages Possum and Horatius infect Pectobacterium versatile, a phytopathogen causing soft rot in potatoes and other essential plants. Their properties and genomic composition define them as N4-like bacteriophages of the genus Cbunavirus, a part of a recently formed family Schitoviridae. It is proposed that the adsorption apparatus of these phages consists of tail fibers connected to the virion through an adapter protein. Tail fibers possess an enzymatic domain. Phage Possum uses it to deacetylate O-polysaccharide on the surface of the host strain to provide viral attachment. Such an infection mechanism is supposed to be common for all Cbunavirus phages and this feature should be considered when designing cocktails for phage control of soft rot.

Bacteriostatic effects of phage F23s1 and its endolysin on Vibrio parahaemolyticus

Vibrio parahaemolyticus is a common foodborne pathogenic bacterium and drug-resistant strains are now widespread. Phages led by drug-resistant V. parahaemolyticus strains are promising means to decrease the pressure on public health. We isolated a V. parahaemolyticus-specific bacteriophage F23s1 that was active at wide ranges of temperature (30-60°C) and pH (4-10). Phage F23s1 exhibited a specific host range; in that, only 13 of the 23 V. parahaemolyticus strains were lysed. F23s1 effectively inhibited the growth of V. parahaemolyticus strain F23 in shrimp at 25°C within 12 h at a multiplicity of infection of 1000. We sequenced the genome of phage F23s1 which comprised a 76,648-bp DNA with 105 open reading frames (ORFs) and identified an endolysin gene ORF52 that was then cloned and successfully expressed in Escherichia coli. The recombinant ORF52 protein significantly decreased OD_600 nm of V. parahaemolyticus F23 from 0.978 to 0.249 when used at 20 µmol/L within 60 min. The endolysin also showed lytic activity against a panel of 23 drug-resistant V. parahaemolyticus and 12 Salmonella strains with a higher lytic ability for V. parahaemolyticus. The phage F23s1 and its endolysin will be useful for preventing and controlling V. parahaemolyticus in food safety.

Limitations of Phage Therapy and Corresponding Optimization Strategies: A Review

Bacterial infectious diseases cause serious harm to human health. At present, antibiotics are the main drugs used in the treatment of bacterial infectious diseases, but the abuse of antibiotics has led to the rapid increase in drug-resistant bacteria and to the inability to effectively control infections. Bacteriophages are a kind of virus that infects bacteria and archaea, adopting bacteria as their hosts. The use of bacteriophages as antimicrobial agents in the treatment of bacterial diseases is an alternative to antibiotics. At present, phage therapy (PT) has been used in various fields and has provided a new technology for addressing diseases caused by bacterial infections in humans, animals, and plants. PT uses bacteriophages to infect pathogenic bacteria so to stop bacterial infections and treat and prevent related diseases. However, PT has several limitations, due to a narrow host range, the lysogenic phenomenon, the lack of relevant policies, and the lack of pharmacokinetic data. The development of reasonable strategies to overcome these limitations is essential for the further development of this technology. This review article described the current applications and limitations of PT and summarizes the existing solutions for these limitations. This information will be useful for clinicians, people working in agriculture and industry, and basic researchers.

Uses of Bacteriophages as Bacterial Control Tools and Environmental Safety Indicators

Bacteriophages are bacterial-specific viruses and the most abundant biological form on Earth. Each bacterial species possesses one or multiple bacteriophages and the specificity of infection makes them a promising alternative for bacterial control and environmental safety, as a biotechnological tool against pathogenic bacteria, including those resistant to antibiotics. This application can be either directly into foods and food-related environments as biocontrol agents of biofilm formation. In addition, bacteriophages are used for microbial source-tracking and as fecal indicators. The present review will focus on the uses of bacteriophages like bacterial control tools, environmental safety indicators as well as on their contribution to bacterial control in human, animal, and environmental health.

Shotgun metagenomics evaluation of soil fertilization effect on the rhizosphere viral community of maize plants

The need for sustainability in food supply has led to progressive increase in soil nutrient enrichment. Fertilizer application effects both biological and abiotic processes in the soil, of which the bacterial community that support viral multiplication are equally influenced. Nevertheless, little is known on the effect of soil fertilization on the Soil viral community composition and dynamics. In this study, we evaluated the influence of soil fertilization on the maize rhizosphere viral community growing in Luvisolic soil. The highest abundance of bacteriophages were detected in soil treated with 8 tons/ha compost manure (Cp8), 60 kg/ha inorganic fertilizer (N1), 4 tons/ha compost manure (Cp4) and the unfertilized control (Cn0). Our result showed higher relative abundance of Myoviridae, Podoviridae and Siphoviridae in 8 tons/ha organic manure (Cp8) fertilized compared to others. While Inoviridae and Microviridae were the most relative abundant phage families in 4 tons/ha organic manure (Cp4) fertilized soil. This demonstrate that soil fertilization with organic manure increases the abundance and diversity of viruses in the soil due to its soil conditioning effects.

Phages for Africa: The Potential Benefit and Challenges of Phage Therapy for the Livestock Sector in Sub-Saharan Africa

One of the world’s fastest-growing human populations is in Sub-Saharan Africa (SSA), accounting for more than 950 million people, which is approximately 13% of the global population. Livestock farming is vital to SSA as a source of food supply, employment, and income. With this population increase, meeting this demand and the choice for a greater income and dietary options come at a cost and lead to the spread of zoonotic diseases to humans. To control these diseases, farmers have opted to rely heavily on antibiotics more often to prevent disease than for treatment. The constant use of antibiotics causes a selective pressure to build resistant bacteria resulting in the emergence and spread of multi-drug resistant (MDR) organisms in the environment. This necessitates the use of alternatives such as bacteriophages in curbing zoonotic pathogens. This review covers the underlying problems of antibiotic use and resistance associated with livestock farming in SSA, bacteriophages as a suitable alternative, what attributes contribute to making bacteriophages potentially valuable for SSA and recent research on bacteriophages in Africa. Furthermore, other topics discussed include the creation of phage biobanks and the challenges facing this kind of advancement, and the regulatory aspects of phage development in SSA with a focus on Kenya.

Tailed Lytic Bacteriophages of Soft Rot Pectobacteriaceae

The study of the ecological and evolutionary traits of Soft Rot Pectobacteriaceae (SRP) comprising genera Pectobacterium and Dickeya often involves bacterial viruses (bacteriophages). Bacteriophages are considered to be a prospective tool for the ecologically safe and highly specific protection of plants and harvests from bacterial diseases. Information concerning bacteriophages has been growing rapidly in recent years, and this has included new genomics-based principles of taxonomic distribution. In this review, we summarise the data on phages infecting Pectobacterium and Dickeya that are available in publications and genomic databases. The analysis highlights not only major genomic properties that assign phages to taxonomic families and genera, but also the features that make them potentially suitable for phage control applications. Specifically, there is a discussion of the molecular mechanisms of receptor recognition by the phages and problems concerning the evolution of phage-resistant mutants.

Phages in Food Industry Biocontrol and Bioremediation

Bacteriophages are ubiquitous in nature and their use is a current promising alternative in biological control. Multidrug resistant (MDR) bacterial strains are present in the livestock industry and phages are attractive candidates to eliminate them and their biofilms. This alternative therapy also reduces the non-desirable effects produced by chemicals on food. The World Health Organization (WHO) estimates that around 420,000 people die due to a foodborne illness annually, suggesting that an improvement in food biocontrol is desirable. This review summarizes relevant studies of phage use in biocontrol focusing on treatments in live animals, plants, surfaces, foods, wastewaters and bioremediation.

Phages in Food Industry Biocontrol and Bioremediation

Bacteriophages are ubiquitous in nature and their use is a current promising alternative in biological control. Multidrug resistant (MDR) bacterial strains are present in the livestock industry and phages are attractive candidates to eliminate them and their biofilms. This alternative therapy also reduces the non-desirable effects produced by chemicals on food. The World Health Organization (WHO) estimates that around 420,000 people die due to a foodborne illness annually, suggesting that an improvement in food biocontrol is desirable. This review summarizes relevant studies of phage use in biocontrol focusing on treatments in live animals, plants, surfaces, foods, wastewaters and bioremediation.

Use of a Specific Phage Cocktail for Soft Rot Control on Ware Potatoes: A Case Study

Using bacteriophages (bacterial viruses) to control pathogenic bacteria is a promising approach in horticulture. However, the application of this strategy in real conditions requires compliance with particular technological and environmental restraints. The presented paper concerns the process of phage selection to create a cocktail that is efficient against the circulating causal agents of potato soft rot. The resulting phage cocktail causes a complete lysis of a mixture of circulating pectobacterial strains in vitro. In the context of being used to treat ware potatoes during off-season storage, the protocol of phage application via the humidity maintenance system was designed. The phage cocktail was shown to reduce the population of Pectobacterium spp. 10-12-fold, achieving a population that was below a symptomatic threshold.

Pectobacterium brasiliense: Genomics, Host Range and Disease Management

Pectobacterium brasiliense (Pbr) is considered as one of the most virulent species among the Pectobacteriaceae. This species has a broad host range within horticulture crops and is well distributed elsewhere. It has been found to be pathogenic not only in the field causing blackleg and soft rot of potato, but it is also transmitted via storage causing soft rot of other vegetables. Genomic analysis and other cost-effective molecular detection methods such as a quantitative polymerase chain reaction (qPCR) are essential to investigate the ecology and pathogenesis of the Pbr. The lack of fast, field deployable point-of-care testing (POCT) methods, specific control strategies and current limited genomic knowledge make management of this species difficult. Thus far, no comprehensive review exists about Pbr, however there is an intense need to research the biology, detection, pathogenicity and management of Pbr, not only because of its fast distribution across Europe and other countries but also due to its increased survival to various climatic conditions. This review outlines the information available in peer-reviewed literature regarding host range, detection methods, genomics, geographical distribution, nomenclature and taxonomical evolution along with some of the possible management and control strategies. In summary, the conclusions and a further directions highlight the management of this species.

The future of phage biocontrol in integrated plant protection for sustainable crop production

Bacterial phytopathogens significantly reduce crop yields and hence, pose a threat to the food supply of our increasing world population. In this context, bacteriophages are investigated as potential sustainable biocontrol agents. Here, recent advances in phage biocontrol are reviewed and considered within the framework of integrated plant protection strategies. This shows that understanding the pathogen's biology is crucial to develop a targeted strategy, tailored to individual pathosystems and driven by biotechnological insights. Moreover, the potential synergy of phages in contemporary farming practices based on the Internet of Things is proposed, potentially enabling a timely and cost-efficient treatment of plants at an early stage of the disease. Finally, these prospects are placed in the regulatory context of virus-oriented integrated pest control.

Population Dynamics between Erwinia amylovora, Pantoea agglomerans and Bacteriophages: Exploiting Synergy and Competition to Improve Phage Cocktail Efficacy

Bacteriophages are viruses capable of recognizing with high specificity, propagating inside of, and destroying their bacterial hosts. The phage lytic life cycle makes phages attractive as tools to selectively kill pathogenic bacteria with minimal impact on the surrounding microbiome. To effectively harness the potential of phages in therapy, it is critical to understand the phage–host dynamics and how these interactions can change in complex populations. Our model examined the interactions between the plant pathogen Erwinia amylovora, the antagonistic epiphyte Pantoea agglomerans, and the bacteriophages that infect and kill both species. P. agglomerans strains are used as a phage carrier; their role is to deliver and propagate the bacteriophages on the plant surface prior to the arrival of the pathogen. Using liquid cultures, the populations of the pathogen, carrier, and phages were tracked over time with quantitative real-time PCR. The jumbo Myoviridae phage ϕEa35-70 synergized with both the Myoviridae ϕEa21-4 and Podoviridae ϕEa46-1-A1 and was most effective in combination at reducing E. amylovora growth over 24 h. Phage ϕEa35-70, however, also reduced the growth of P. agglomerans. Phage cocktails of ϕEa21-4, ϕEa46-1-A1, and ϕEa35-70 at multiplicities of infections (MOIs) of 10, 1, and 0.01, respectively, no longer inhibited growth of P. agglomerans. When this cocktail was grown with P. agglomerans for 8 h prior to pathogen introduction, pathogen growth was reduced by over four log units over 24 h. These findings present a novel approach to study complex phage–host dynamics that can be exploited to create more effective phage-based therapies.

Isolation and Characterization of Pectobacterium Phage vB_PatM_CB7: New Insights into the Genus Certrevirus

To date, Certrevirus is one of two genera of bacteriophage (phage), with phages infecting Pectobacterium atrosepticum, an economically important phytopathogen that causes potato blackleg and soft rot disease. This study provides a detailed description of Pectobacterium phage CB7 (vB_PatM_CB7), which specifically infects P. atrosepticum. Host range, morphology, latent period, burst size and stability at different conditions of temperature and pH were examined. Analysis of its genome (142.8 kbp) shows that the phage forms a new species of Certrevirus, sharing sequence similarity with other members, highlighting conservation within the genus. Conserved elements include a putative early promoter like that of the Escherichia coli sigma70 promoter, which was found to be shared with other genus members. A number of dissimilarities were observed, relating to DNA methylation and nucleotide metabolism. Some members do not have homologues of a cytosine methylase and anaerobic nucleotide reductase subunits NrdD and NrdG, respectively. Furthermore, the genome of CB7 contains one of the largest numbers of homing endonucleases described in a single phage genome in the literature to date, with a total of 23 belonging to the HNH and LAGLIDADG families. Analysis by RT-PCR of the HNH homing endonuclease residing within introns of genes for the large terminase, DNA polymerase, ribonucleotide reductase subunits NrdA and NrdB show that they are splicing competent. Electrospray ionization-tandem mass spectrometry (ESI-MS/MS) was also performed on the virion of CB7, allowing the identification of 26 structural proteins-20 of which were found to be shared with the type phages of the genera of Vequintavirus and Seunavirus. The results of this study provide greater insights into the phages of the Certrevirus genus as well as the subfamily Vequintavirinae.