Search Results (149)

This study characterizes AP-20-A, a lytic podovirus infecting Sinorhizobium meliloti, isolated from agricultural chernozem. Its 49.4 kbp genome shows negligible intergenomic similarity with known rhizobiophages (<2%). Core structural proteins—the major capsid protein (MCP) and terminase large subunit (TerL)—show closest homology to podoviruses infecting Paenibacillus, rather than to alphaproteobacterial viruses, suggesting cross-phylum horizontal gene transfer. This exchange is ecologically plausible, as Paenibacillus and Sinorhizobium co-exist in the rhizosphere. Over 63% of predicted proteins are functionally uncharacterized, with structural homologs detected in bacteria, archaea, and eukaryotes. We report the first identification in a rhizobiophage of a Tad2-like domain, predicted to block the bacterial Thoeris type II anti-phage defense. AP-20-A infected 56% of native S. meliloti strains; agrocenose isolates showed higher resistance than phytocenose isolates, evidence of local co-evolution. Among susceptible strains, 60% entered putative pseudolysogeny (with one strain exhibiting growth stimulation), whereas a symbiotically elite inoculant strain was completely lysed within hours. Some host strains carry additional AbiE systems; whether these independent defense–counterdefense layers interact during infection remains unknown. We conclude that resident phages represent a selective force that can disrupt inoculant establishment, underscoring the need to integrate soil virome assessment into agricultural microbiome management. Full article

Background: Escherichia coli remains a critical multidrug-resistant nosocomial pathogen, driving interest in bacteriophage-based biocontrol. The genus Kayfunavirus (family Autotranscriptaviridae) exhibits obligately lytic replication cycles and favorable biosafety profiles, yet each new phage requires comprehensive genomic characterization to expand therapeutic candidate pools. This study aimed to isolate and genomically characterize a novel Kayfunavirus from an environmental reservoir in Vietnam. Methods: Escherichia phage vB_EcoA-Sparklingdew was isolated from Can Tho River water using host E. coli AgE9. The genome was assembled using SPAdes. The termini were resolved with PhageTerm. The annotation was done via the Pharokka pipeline and HHpred. Taxonomic classification was performed using taxMyPhage, VIRIDIC intergenomic comparisons, and maximum likelihood phylogeny of concatenated structural proteins. Results: The complete genome comprises a 37,944 bp linear dsDNA molecule (49.9% GC), encoding 51 open reading frames in a predominantly unidirectional arrangement. Key features include a virion-encoded T7-like RNA polymerase, a 723-residue T7-like DNA polymerase, a canonical lysis triad, and two putative tailspike proteins. A 212 bp direct terminal repeat and coverage profiles support a headful (pac) packaging mechanism. Comprehensive screening confirmed the absence of lysogeny, virulence, and antibiotic resistance determinants. A single synonymous SNP indicated high clonal purity. Intergenomic identity peaked at 87.7% against ICTV references, confirming placement in a novel species. Conclusions: Phage Sparklingdew represents a strictly lytic Kayfunavirus with a compact genomic architecture. Its favorable safety profile and absence of temperate markers support further evaluation for targeted therapeutic applications against pathogenic E. coli. Full article

Background/Objectives: Skin and soft tissue infections (SSTIs) represent a significant clinical challenge, largely due to the high prevalence of antibiotic-resistant Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA). Treatment is further complicated by biofilm formation, which reduces antibiotic efficacy. The limitations of conventional therapies highlight the need for alternative approaches. Phage therapy has emerged as a promising biological strategy; however, its effectiveness may be constrained by factors such as phage instability and biofilm regrowth. This study aimed to enhance phage-based treatment by combining a newly isolated phage, vB_Sau-E, with lactoferrin (Lf), a multifunctional protein of the innate immune system. Methods: Phage vB_Sau-E was characterized in terms of its infection dynamics and lytic activity. Biocompatibility was further examined using human skin cell lines. The potential effect of Lf was assessed by evaluating its impact on phage infectivity and stability under a range of environmental conditions and by checkerboard assay. Results: Phage vB_Sau-E belongs to the Silviavirus genus in the Herelleviridae family. It was shown to infect 12 out of 22 tested clinical MRSA isolates, with 10 strains identified as good hosts. The phage has a ~30 min life cycle, and ~50 progeny virions are released after bacterial cell lysis. We have also observed that Lf increased plating efficiency and enhanced phage stability at a pH of 5.5 and at −20° C. It also proved to have an additive antibacterial effect, though this was observed to be strain-dependent. Conclusions: Lactoferrin functions as a stabilizing adjuvant for phage vB_Sau-E. Its additive effect supports the development of more effective, biofilm-targeting therapies for staphylococcal SSTIs. Full article

Antimicrobial resistance (AMR) has become a major concern in the treatment of bacterial infections, and bacteriophage therapy has emerged as a promising alternative to antibiotics. Bacteriophages are highly specific to their bacterial hosts; hence, isolating phages indigenous to a specific region offers a significant advantage against various pathogen strains. We have isolated a cocktail of bacteriophages against pathogenic E. coli from sewage water at a primary healthcare centre. Characterisation of the isolated phages demonstrated their stability across a broad pH and temperature range, strong lytic activity, and effective biofilm degradation, with no cross-reactivity with Staphylococcus aureus (S. aureus). Genomic analysis and phylogenetic studies indicated that the largest phage (by genome size) in the cocktail belongs to the genus Vequintavirus (myoviruses, rV5-like phages), and its genome sequence has been deposited in NCBI (Accession ID: PX741096). The phage genome was linear, with headful (PAC) packaging, encoded lysis proteins, and lacked antibiotic-resistant or major lysogeny-associated genes, collectively suggesting a lytic lifestyle. These findings emphasize the therapeutic potential of rV5-like phages and underscore the critical need to establish phage banks in India to improve disease management. Full article

Chryseobacterium indologenes MA9 is a causative agent of root rot disease in Panax notoginseng (P. notoginseng), with its high incidence being a major manifestation of continuous cropping barriers, severely hindering the sustainable development of the P. notoginseng industry. In this study, a novel lytic bacteriophage, MA9V-3, was isolated from wastewater, targeting C. indologenes MA9. The phage produced clear plaques, ranging from 1 to 3 mm in diameter, with a surrounding halo. Phage MA9V-3 achieved an adsorption rate of up to 80% after 30 min of contact with C. indologenes MA9, a latent period of approximately 40 min, and an average burst-size if 160 PFU/cell. Transmission electron microscopy revealed that phage MA9V-3 possesses an icosahedral head and a contractile tail, exhibiting a typical myovirus-like morphology. According to the latest ICTV taxonomy, MA9V-3 belongs to the class Caudoviricetes, and the phage’s biocontrol efficacy and inhibitory capacity were evaluated at different multiplicity of infection (MOI s). The results showed that the highest titer recorded at 1.6 × 10¹⁰ PFU/mL. Whole-genome sequencing revealed that MA9V-3 is a double-stranded circular DNA virus, with a genome length of 103,203 bp, GC content of 34.29%, and 150 open reading frames (ORFs), one of which is related to tRNA. Only 13 of these ORFs encode known functional sequences, likely due to the limited available gene data for such phages in the database, with additional details on hypothetical proteins yet to be uncovered. Comparative database analysis confirmed that the phage genome contains no antibiotic resistance or toxin-related genes. Phage therapy experiments were performed using MA9V-3 and two other phages screened in our laboratory. The experimental results showed that phage MA9V-3 may be a potential candidate for effectively controlling the infection of Panax notoginseng by C. indologenes MA9, and offering valuable insights into the potential application of phage therapy for managing bacterial plant diseases. Full article

Burkholderia pseudomallei, the causative agent of melioidosis, presents significant challenges in both treatment and environmental decontamination. Bacteriophages, or phages, are increasingly being explored as potential diagnostic, therapeutic, and biocontrol agents against this bacterial pathogen. Our recent investigation has shown that most B. pseudomallei genomes contained prophage(s) associated with specific tRNA gene loci, prompting us to explore these detectable prophages as sources of temperate phages for further applications. Transcriptomic profiling of B. pseudomallei Bp82, a model strain that possesses three different prophages, revealed high expression levels of the integrase and certain transcriptional regulatory genes within its prophages during normal exponential growth. Using one of its temperate phages, namely φBP82.2, a P2-like phage, as a model, we investigated the lysogenic–lytic control mechanisms. Mutagenesis of the integrase gene, phiBP82.2_gp51, did not improve killing activity compared to the wildtype phage. In contrast, deletion of phiBP82.2_gp38, a putative transcriptional regulatory gene, and two downstream hypothetical protein genes, phiBP82.2_gp36 and phiBP82.2_gp37, resulted in significant lytic improvement. We conclude that these genes play a crucial role in the lysogenic–lytic switch of φBP82.2, suggesting a new avenue for engineering temperate phages for future applications. Full article

The escalation of bacterial resistance to existing antibiotics represents a growing global health challenge, exacerbated by the widespread misuse of antimicrobial agents. As a result, alternative antibacterial strategies are increasingly being explored, including phage-derived lytic proteins. In this study, we report a preliminary characterisation of a novel phage-derived lytic protein identified through computational screening of bacteriophage genome sequences. A putative open reading frame, designated SM07 (1383 bp), was selected from bacteriophage sequences contributed by the University of KwaZulu-Natal to a global phage repository. The gene was synthesised, sub-cloned into the pET-30b(+) vector with an N-terminal histidine tag, and recombinantly expressed in Escherichia coli BL-21(AI) cells. The protein was purified using affinity and ion-exchange chromatography. Purified SM07 exhibited in vitro antimicrobial activity against Pseudomonas aeruginosa, with a minimum inhibitory concentration of 4 µg/mL, while no significant cytotoxic effects were observed in Vero kidney cells at concentrations substantially above the effective dose. Together, these findings provide initial evidence supporting the antimicrobial potential of SM07 and highlight phage-derived lytic proteins as candidates for further investigation as alternative agents against P. aeruginosa-associated infections. Full article

Bacteriophages are powerful drivers of microbial evolution and are increasingly explored as alternatives to antibiotics against multidrug-resistant pathogens such as Pseudomonas aeruginosa. Here, we describe the isolation, phenotypic characterization and genomic, structural and evolutionary analysis of Pseudomonas phage Adele, a lytic myovirus representing a novel species within the genus Pakpunavirus (family Vandenendeviridae). Phage Adele exhibits a short latent period of 20 min, a burst size of 59 ± 11 virions per infected cell and a high virulence index, efficiently lysing non-O11 Pseudomonas aeruginosa strains and reducing biofilm biomass. In vivo, Adele confers marked protection in a Galleria mellonella infection model. Phylogenetic reconstruction, synteny analysis and structural modeling demonstrate the relatedness of Vandenendeviridae to phages of the Andersonviridae and Vequintavirinae clades, pointing to a stable, ancestral virion architecture that has undergone lineage-specific elaborations, including the duplication and divergence of tail tube proteins. The tail assembly chaperone gene employs a conserved −1 programmed ribosomal frameshift. Phage Adele encodes an elaborate set of metabolic reprogramming and anti-defense systems, reflecting extensive horizontal gene transfer. The combination of a conserved structural architecture and mosaic genome establishes Adele as an exemplary system for studying modular evolution in phages, alongside its demonstrated therapeutic efficacy. Full article

This study characterizes two novel Bacillus phages, B450T and B450C, isolated from Bacillus thuringiensis VKM B-450 via mitomycin C induction, along with their endolysin, PlyC19. Both phages, siphoviruses with 41,205 bp genomes, lysed 38% of the tested Bacillus cereus sensu lato strains, with B450C showing enhanced lytic activity due to mutations in the repressor protein. PlyC19 lysed 56% of the strains tested, including Priestia flexa, demonstrating broader efficacy. Its Amidase_2 domain and dual SH3 cell wall-binding domains enable targeted peptidoglycan hydrolysis, with optimal activity at pH 9.0 and thermal stability up to 40 °C. We propose the taxonomic designation Bquatquinnuvirus eskimopiis for these phages, with B450T and B450C representing distinct strains, based on genomic divergence in the repressor protein’s HTH_Xre domain, consistent with their turbid and clear plaque morphologies, respectively. PlyC19′s broad specificity underscores its potential as an enzybiotic against multidrug-resistant Bacillus cereus group strains in food safety and medicine. Full article

Despite being a commensal bacterium, Cutibacterium acnes has been widely considered a major opportunistic pathogen due to its capacity for biofilm production and inflammatory induction, causing device-related, post-implant infections, and skin inflammatory diseases. In this study, we isolated and characterised the novel bacteriophage Cutibacterium acnes phage KIT09 as a potential antimicrobial candidate for the treatment of Cutibacterium acnes-related infections such as acne vulgaris and postsurgical infections. Subsequently, phage-resistant bacterial mutants were generated through phage KIT09 exposure and characterised. Wastewater samples were collected for the isolation of C. acnes phages, followed by their characterisation using C. acnes National Institute of Technology and Evaluation (NITE) Biological Resources Center (NBRC) 107605 (phylotype IA1). Resistant mutants were isolated after prolonged exposure of the newly isolated phage to host bacteria and then characterised. A novel C. acnes phage, designated KIT09, was isolated, demonstrating prolonged bacteriolysis lasting up to 96 h at a multiplicity of infection of 10, and exhibiting high thermal and pH stability. Following sustained selective pressure by phage KIT09, three phage-resistant bacterial isolates were obtained, forming smaller colonies than the wild-type strain, but maintaining a high phage adsorption capacity (>90% after 20 min). Whole-genome sequencing revealed 12 nucleotide mutations across five genes, including six non-synonymous substitutions. Three genes encoding a two-component histidine kinase, DNA processing protein A (DprA), and a ThuA-containing domain protein were mutated in all resistant isolates. Characterisation of the novel phage KIT09 demonstrated its robust lytic activity and environmental stability against C. acnes phylotype IA1. Isolated resistant mutants retained high phage adsorption, accompanied by recurrent mutations in genes encoding a two-component histidine kinase, DprA, and a ThuA-domain protein, suggesting the presence of alternative, CRISPR-Cas–independent resistance mechanisms in C. acnes. Full article

Background/Objectives: Klebsiella pneumoniae is a clinically important pathogen that causes respiratory tract infections, pneumonia, wound infections, urinary tract infections, and sepsis. It is on the World Health Organization (WHO) priority pathogen list as it causes antimicrobial-resistant infections. The aim of this study was to isolate bacteriophages against pan-resistant K. pneumoniae isolated from clinical wound infections. Results: One of the isolated phages, CTF-1, possesses a linear double-stranded DNA genome that is 40,841 base pairs (bp) long and contains 44 predicted genes. Functional assignments were made for 31 of the predicted gene products, which are associated with genome replication, phage packaging, structural proteins, and host lysis, leaving 13 annotated as hypothetical proteins. Based on sequencing analysis, phage CTF-1 is a new member of the genus Przondovirus within the order Autographivirales. Phage CTF-1 was effective against 22 of 25 (88%) pan-resistant K. pneumoniae isolates. The latent period and lytic cycle of the phage were approximately 40 min, with a burst size of about 92 PFU/mL. Conclusions: Our findings suggest that Klebsiella phage CTF-1 is an excellent candidate for phage therapy due to its high lytic activity against pan-resistant K. pneumoniae strains and lack of genes encoding antibiotic resistance, toxins, virulence factors, or integrases. Full article

The emergence of multidrug-resistant Shiga toxin-producing Escherichia coli (STEC) poses a major challenge to public health and necessitates the development of alternative antimicrobial strategies. This study aimed to isolate and characterize five lytic bacteriophages belonging to the genus Mosigvirus and evaluate their potential as biocontrol against MDR STEC strains and their biofilms. The five bacteriophages, designated vB_EcoM-pJBB (ΦB), vB_EcoM-pJBC (ΦC), vB_EcoM-pJBJ (ΦJ), vB_EcoM-pJBK (ΦK), and vB_EcoM-pJBL (ΦL), were isolated from sewage treatment plant samples using STEC ATCC 43895 as host. Biological characterization included host range determination against 19 MDR STEC strains, one-step growth analysis, environmental stability assays, bacteriolytic activity assessment, and antibiofilm efficacy testing. Whole-genome sequencing and phylogenetic analyses were performed to determine genomic features and taxonomic classification. The phages demonstrated varying infectious capacities, lysing between six and 12 strains, with ΦL exhibiting the broadest spectrum of activity. All phages showed MOI-independent antibiofilm activity, preventing biofilm formation by approximately 70% and disrupting pre-formed biofilms by up to 80.3%. Genomic analysis revealed the absence of lysogeny markers, virulence factors, and antimicrobial resistance genes, while identifying putative depolymerase genes associated with tail fiber proteins. Phylogenetic analysis confirmed the taxonomic position of these phages within the Mosigvirus genus in the Straboviridae family. Our findings indicate that the newly identified Mosigvirus phages are promising candidates for phage-based biocontrol applications. Full article

Capsular polysaccharides are critical virulence factors of Klebsiella pneumoniae, enabling the bacterium to evade host immune recognition and exacerbate infection. Phage-derived depolymerases, which specifically degrade these capsular polysaccharides, are increasingly recognized as a highly promising strategy for the treatment of bacterial infections. In the present study, we isolated and characterized a lytic Klebsiella pneumoniae phage, named phiTH1, and sequenced its genome. The K30-type capsular polysaccharide was identified as the receptor for phiTH1 infection. A tail fiber protein with a pectate lyase domain, Dop5, was then recognized as a potential K30-type depolymerase. Therefore, the recombinant protein Dop5 was expressed in Escherichia coli and purified, and its in vitro capsular depolymerase activity was demonstrated. Further, by using a murine aspiration pneumonia model induced by K30-type Klebsiella pneumoniae TH1, we found that Dop5 protected 80% of mice from lethal challenge with Klebsiella pneumoniae. After Dop5 treatment, the pathological damage in multiple organs of mice was alleviated, the bacterial load was reduced, and serum levels of inflammatory cytokines and complement C3 decreased, along with a significant reduction in the pathological score of the lungs. Hence, this study revealed the potential of the depolymerase Dop5 for the treatment of Klebsiella pneumoniae infections. Full article

The focus of this study was to explore phage display systems employing bacteriophage lambda (λ) gene fusions to its capsid decoration protein gpD as reagent tools for tackling disease. The biological activity of gpD-fusions was examined by testing for the retained antimicrobial toxicity of cathelicidins or defensins fused to gpD. Our previous finding that only COOH fusions of either cathelicidins or defensins to gpD were toxigenic was expanded to show that only the reduced form of fused defensin antimicrobial polypeptides was found to be toxigenic. Compared in review are gene-fusion lytic display systems (where the fusion-display gene is integrated within the viral genome) with a surrogate system, employed herein, that exogenously provides the fusion-display protein for addition to phage capsid. It is easily possible to produce fully coated lambda display particles (LDP) serving as single epitope vaccines (SEV), or antimicrobials, or to produce partially coated LDP without any complex bacteriophage genetic engineering, making the system available to all. The potential to build vaccine vector phage particles (LDNAP) comprising essentially sheathed DNA vaccines encapsulated within an environmentally protective capsid is described. LDNAP are produced by introducing a cassette into the phage genome either by phage–plasmid recombination or cloning. The cassette carries a high-level eukaryotic expression promoter driving transcription of the vaccine candidate gene and is devoid of plasmid resistance elements. Full article

Bacteriophages, or phages, are sophisticated nanomachines that efficiently infect bacteria. Their infection of lactic acid bacteria (LAB) used in fermentation can lead to significant industrial losses. Among phages that infect monoderm bacteria, those with siphovirion morphology characterized by a long, non-contractile tail are predominant. The initial stage of phage infection involves precise host recognition and binding. To achieve this, phages feature host adhesion devices (HADs) located at the distal end of their tails, which have evolved to recognize specific proteinaceous or saccharidic receptors on the host cell wall. Ceduovirus represents a group of unique lytic siphophages that specifically infect the LAB Lactococcus lactis by targeting proteinaceous receptors. Despite having compact genomes, most of their structural genes are poorly annotated and the architecture and function of their HADs remain unknown. Here we used AlphaFold3 to explore the Ceduovirus HADs and their interaction with the host. We show that Ceduovirus HADs exhibit unprecedented features among bacteriophages infecting Gram⁺, share structural similarities with bacterial secretion system VI, and combine both saccharide and protein-binding modules. Moreover, we could annotate the majority of Ceduovirus genes encoding structural proteins by leveraging their predicted structures, highlighting AlphaFold’s significant contribution to phage genome annotation. Full article