Infection Kinetics and Phylogenetic Analysis of vB_EcoD_SU57, a Virulent T1-Like Drexlerviridae Coliphage

Potential of a newly isolated lytic bacteriophage to control Pseudomonas coronafaciens pv. garcae in coffee plants: Molecular characterization with in vitro and ex vivo experiments

Traditionally, control of coffee plant bacterial halo blight (BHB) caused by the phytopathogen Pseudomonas coronafaciens pv. garcae (Pcg) involves frequent spraying of coffee plantations with non-environmentally friendly and potentially bacterial resistance-promoting copper products or with kasugamycin hydrochloride. In this study we report a leap forward in the quest for a new ecofriendly approach, characterizing (both physicochemically and biologically) and testing both in vitro and ex vivo a new lytic phage for Pcg. An in-depth molecular (genomic and DNA structural features) characterization of the phage was also undertaken. Phage PcgS01F belongs to the class Caudoviricetes, Drexlerviridae family and genus Guelphvirus, and presents a siphovirus-like morphotype. Phage PcgS01F showed a latency period of 40 min and a burst size of 46 PFU/host cell, allowing to conclude that it replicates well in Pcg IBSBF-158. At Multiplicity Of Infection (MOI, or the ratio of phage to bacteria) 1000, the performance of phage PcgS01F was much better than at MOI 10, promoting increasing bacterial reductions until the end of the in vitro inactivation assays, stabilizing at a significant 82 % bacterial load reduction. Phage PcgS01F infected and killed Pcg cells ex vivo in coffee plant leaves artificially contaminated, with a maximum of Pcg inactivation of 7.66 log CFU/mL at MOI 1000 after 36 h of incubation. This study provides evidence that the isolated phage is a promising candidate against the causative agent of BHB in coffee plants.

The TolC and Lipopolysaccharide-Specific Escherichia coli Bacteriophage TLS-the Tlsvirus Archetype Virus

Introduction

TLS is a virulent bacteriophage of Escherichia coli that utilizes TolC and lipopolysaccharide as its cell surface receptors.

Methods

The genome was reannotated using the latest online resources and compared to other T1-like phages.

Results

The TLS genome consists of 49,902 base pairs, encoding 86 coding sequences that display considerable sequence similarity with the T1 phage genome. It also contains 18 intergenic 21-base long repeats, each of them upstream of a predicted start codon and in the direction of transcription. Data revealed that DNA packaging occurs through the pac site-mediated headful mechanism.

Conclusions

Based on sequence analysis of its genome, TLS belongs to the Drexlerviridae family and represents the type member of the Tlsvirus genus.

Genomic and biological insights of bacteriophages JNUWH1 and JNUWD in the arms race against bacterial resistance

The coevolution of bacteria and bacteriophages has created a great diversity of mechanisms by which bacteria fight phage infection, and an equivalent diversity of mechanisms by which phages subvert bacterial immunity. Effective and continuous evolution by phages is necessary to deal with coevolving bacteria. In this study, to better understand the connection between phage genes and host range, we examine the isolation and genomic characterization of two bacteriophages, JNUWH1 and JNUWD, capable of infecting Escherichia coli. Sourced from factory fermentation pollutants, these phages were classified within the Siphoviridae family through TEM and comparative genomic analysis. Notably, the phages exhibited a viral burst size of 500 and 1,000 PFU/cell, with latent periods of 15 and 20 min, respectively. They displayed stability over a pH range of 5 to 10, with optimal activity at 37°C. The complete genomes of JNUWH1 and JNUWD were 44,785 bp and 43,818 bp, respectively. Phylogenetic analysis revealed their close genetic relationship to each other. Antibacterial assays demonstrated the phages' ability to inhibit E. coli growth for up to 24 h. Finally, through laboratory-driven adaptive evolution, we successfully identified strains for both JNUWH1 and JNUWD with mutations in receptors specifically targeting lipopolysaccharides (LPS) and the lptD gene. Overall, these phages hold promise as additives in fermentation products to counter E. coli, offering potential solutions in the context of evolving bacterial resistance.

In vitro and in vivo evaluation of the biofilm-degrading Pseudomonas phage Motto, as a candidate for phage therapy

Infections caused by Pseudomonas aeruginosa are becoming increasingly difficult to treat due to the emergence of strains that have acquired multidrug resistance. Therefore, phage therapy has gained attention as an alternative to the treatment of pseudomonal infections. Phages are not only bactericidal but occasionally show activity against biofilm as well. In this study, we describe the Pseudomonas phage Motto, a T1-like phage that can clear P. aeruginosa infections in an animal model and also exhibits biofilm-degrading properties. The phage has a substantial anti-biofilm activity against strong biofilm-producing isolates (n = 10), with at least a twofold reduction within 24 h. To demonstrate the safety of using phage Motto, cytotoxicity studies were conducted with human cell lines (HEK 293 and RAW 264.7 macrophages). Using a previously established in vivo model, we demonstrated the efficacy of Motto in Caenorhabditis elegans, with a 90% survival rate when treated with the phage at a multiplicity of infection of 10.

Characterization, taxonomic classification, and genomic analysis of two newly isolated bacteriophages with potential to infect Escherichia coli

Escherichia coli is a pathogenic bacterium that is widely distributed and can lead to serious illnesses in both humans and animals. As there is rising incidence of multidrug resistance among these bacteria, it has become imperative to discover alternative therapies beyond antibiotics to effectively treat such infections. Bacteriophage (phage) therapy has the potential to treat infections caused by E. coli, as phages contain enzymes that can cause lysis or destruction of bacterial cells. Simultaneously, the easy accessibility and cost-effectiveness of next-generation sequencing technologies have led to the accumulation of a vast amount of phage sequence data. Here, phages IME177 and IME267 were isolated from sewage water of a hospital in China. Modern phylogenetic approaches and key findings from the genomic analysis revealed that phages IME177 and IME267 are classified as members of the Kayfunavirus genus, Autographiviridae family, and a newly proposed Suseptimavirus genus under subfamily Gordonclarkvirinae, respectively. Further, the Kuravirus genus reshaped into three different genera: Kuravirus, Nieuwekanaalvirus, and Suspeptimavirus, which are classified together under a higher taxonomic rank (subfamily) named Gordonclarkvirinae. No genes related to virulence were detected in the genomes of the phages IME177 and IME267. Both phages exhibited a high degree of resilience to a wide range of conditions, including pH, temperature, exposure to chloroform, and UV radiation. Phages IME177 and IME267 are promising biological agents that can infect E. coli, making them suitable candidates for use in phage therapies.IMPORTANCEBiological and taxonomic characterization of phages is essential for facilitating the development of effective strategies for phage therapy and disease control. Escherichia coli phages are incredibly diverse, and their isolation and classification help us understand the scope and nature of this diversity. By identifying new phages and grouping them into families, we can better understand the genetic and structural variations between phages and how they affect their infectivity and interactions with bacteria. Overall, the isolation and classification of E. coli phages have broad implications for both basic and applied research, clinical practice, and public health.

Targeted Single-Phage Isolation Reveals Phage-Dependent Heterogeneous Infection Dynamics

Due to rising antibiotic resistance, there is an urgent need for different treatment options for multidrug-resistant infections. One alternative under investigation is phage therapy, which uses phages to treat bacterial infections. Although phages are highly abundant in the environment, not all phages are suitable for phage therapy, and finding efficient phages that lack undesirable traits such as bacterial virulence factors is challenging. Here, we developed a targeted single-phage isolation method to detect and isolate phages of interest and to characterize their kinetics in a high-throughput manner. This assay has also revealed cell-to-cell variations at a single-cell level among cells infected with the same phage species, as well as among cells infected with different phage species. IMPORTANCE The spread of multidrug-resistant bacteria is a global human health threat, and without immediate action we are fast approaching a postantibiotic era. One possible alternative to antibiotics is the use of phages, that is, bacterial viruses. However, the isolation of phages that effectively kill their target bacteria has proven challenging. In addition, isolated phages must go through significant characterization before their efficacy is measured. The method developed in this work can isolate single phage particles on the basis of their similarity to previously characterized phages while excluding those with known undesirable traits, such as bacterial toxins, as well as characterizing their kinetics. Using this method, we revealed significant cell-to-cell variations in phage kinetics at a single-cell level among highly virulent phages. These results shed some light on unknown phage-bacterium interactions at the single-cell level.

Isolation and characterization of two homolog phages infecting Pseudomonas aeruginosa

Bacteriophages (phages) are capable of infecting specific bacteria, and therefore can be used as a biological control agent to control bacteria-induced animal, plant, and human diseases. In this study, two homolog phages (named PPAY and PPAT) that infect Pseudomonas aeruginosa PAO1 were isolated and characterized. The results of the phage plaque assay showed that PPAT plaques were transparent dots, while the PPAY plaques were translucent dots with a halo. Transmission electron microscopy results showed that PPAT (65 nm) and PPAY (60 nm) strains are similar in size and have an icosahedral head and a short tail. Therefore, these belong to the short-tailed phage family Podoviridae. One-step growth curves revealed the latent period of 20 min and burst time of 30 min for PPAT and PPAY. The burst size of PPAT (953 PFUs/infected cell) was higher than that of PPAY (457 PFUs/infected cell). Also, the adsorption rate constant of PPAT (5.97 × 10⁻⁷ ml/min) was higher than that of PPAY (1.32 × 10⁻⁷ ml/min) at 5 min. Whole-genome sequencing of phages was carried out using the Illumina HiSeq platform. The genomes of PPAT and PPAY have 54,888 and 50,154 bp, respectively. Only 17 of the 352 predicted ORFs of PPAT could be matched to homologous genes of known function. Likewise, among the 351 predicted ORFs of PPAY, only 18 ORFs could be matched to genes of established functions. Homology and evolutionary analysis indicated that PPAT and PPAY are closely related to PA11. The presence of tail fiber proteins in PPAY but not in PPAT may have contributed to the halo effect of its plaque spots. In all, PPAT and PPAY, newly discovered P. aeruginosa phages, showed growth inhibitory effects on bacteria and can be used for research and clinical purposes.

Population Dynamics of a Two Phages-One Host Infection System Using Escherichia coli Strain ECOR57 and Phages vB_EcoP_SU10 and vB_EcoD_SU57

In this study, we looked at the population dynamics of a two phages-one host system using phages vB_EcoP_SU10 (SU10) and vB_EcoD_SU57 (SU57) and the bacteria Escherichia coli, strain ECOR57. Phage-specific growth curves were observed where infections by SU10 resulted in a moderate production of phages and infections by SU57 resulted in a fast and extensive production of phage progeny. Sequentially adding SU10 followed by SU57 did not produce a significant change in growth rates, whereas adding SU57 followed by SU10 resulted in a decrease in SU10 titer The efficiency of the plating assays showed that ECOR57 exhibited a resistance spectrum after infection by both the single and combined phages. Phage-resistant bacteria exhibited four different morphotypes (i.e., normal, slimy, edgy, and pointy). The normal and edgy morphotypes had a high frequency of developing resistance. Bacterial growth and biofilm assays indicated that the edgy and pointy morphotypes reached a stationary phase faster and produced more biofilm compared to the wild type. These findings suggest that the dynamic structure of phage-bacteria communities dictate resistance evolution and development. Understanding when and how resistances arise and phage(s)-hosts interactions could aid in the design of phage therapy treatments.

Virome in Fecal Samples From Wild Giant Pandas (Ailuropoda Melanoleuca)

The giant panda (Ailuropoda melanoleuca) is one of the most endangered mammals in the world; anthropogenic habitat loss and poaching still threaten the survival of wild pandas. Viral infection has become one of the potential threats to the health of these animals, but the available information related to these infections is still limited. In order to detect possible vertebrate viruses, the virome in the fecal samples of seven wild giant pandas from Qinling Mountains was investigated by using the method of viral metagenomics. From the fecal virome of wild giant pandas, we determined six nearly complete genomes belonging to the order Picornavirales, two of which may be qualified as a novel virus family or genus. In addition, four complete genomes belonging to the Genomoviridae family were also fully characterized. This virological investigation has increased our understanding of the gut viral community in giant pandas. Whether these viruses detected in fecal samples can really infect giant panda needs further research.

Classification of In Vitro Phage-Host Population Growth Dynamics

The therapeutic use of bacteriophages (phage therapy) represents a promising alternative to antibiotics to control bacterial pathogens. However, the understanding of the phage-bacterium interactions and population dynamics seems essential for successful phage therapy implementation. Here, we investigated the effect of three factors: phage species (18 lytic E. coli-infecting phages); bacterial strain (10 APEC strains); and multiplicity of infection (MOI) (MOI 10, 1, and 0.1) on the bacterial growth dynamics. All factors had a significant effect, but the phage appeared to be the most important. The results showed seven distinct growth patterns. The first pattern corresponded to the normal bacterial growth pattern in the absence of a phage. The second pattern was complete bacterial killing. The remaining patterns were in-between, characterised by delayed growth and/or variable killing of the bacterial cells. In conclusion, this study demonstrates that the phage-host dynamics is an important factor in the capacity of a phage to eliminate bacteria. The classified patterns show that this is an essential factor to consider when developing a phage therapy. This methodology can be used to rapidly screen for novel phage candidates for phage therapy. Accordingly, the most promising candidates were phages found in Group 2, characterised by growth dynamics with high bacterial killing.

Complete Genome Sequence of vB_EcoP_SU7, a Podoviridae Coliphage with the Rare C3 Morphotype

Enterotoxigenic Escherichia coli (ETEC) strains are an important cause of bacterial diarrheal illness in humans and animals. Infections arising from ETEC could potentially be treated through the use of bacteriophage (phage) therapy, as phages encode for enzymes capable of bacterial cell lysis. vB_EcoP_SU7 was isolated from the Käppala wastewater treatment plant in Stockholm, Sweden, and propagated on an ETEC strain exhibiting the O:139 serovar. Transmission electron microscopy confirmed that vB_EcoP_SU7 belongs to the Podoviridae family and has the rare C3 morphotype of an elongated head. Bioinformatic analyses showed that the genome was 76,626 base pairs long and contained 35 genes with predicted functions. A total of 81 open reading frames encoding proteins with hypothetical function and two encoding proteins of no significant similarity were also found. A putative tRNA gene, which may aid in vB_EcoP_SU7's translation, was also identified. Phylogenetic analyses showed that compared to other Podoviridae, vB_EcoP_SU7 is a rare Kuravirus and is closely related to E. coli phages with the uncommon C3 morphotype, such as ECBP2, EK010, vB_EcoP_EcoN5, and vB_EcoP_SU10. Phage vB_EcoP_SU7 has a narrow host range, infecting 11 out of the 137 E. coli strains tested, a latency period of 30 min, a burst size of 12 PFU/cell, and an adsorption rate of 8.78 × 10-9 mL/min five minutes post infection. With a limited host range and poor infection kinetics, it is unlikely that SU7 can be a standalone phage used for therapeutic purposes; rather, it must be used in combination with other phages for broad-spectrum therapeutic success.