Search Results (62)

The spread of antibiotic-resistant pathogenic Escherichia coli poses a serious threat to calf health on livestock farms. With the decline in antibiotic therapy effectiveness, alternative approaches such as phage therapy are urgently needed. This study aimed to isolate lytic E. coli bacteriophages, characterize their properties, and evaluate the synergistic effects of their combined use with veterinary antibiotics against colibacillosis pathogens in calves. As a result of the work, 4 bacteriophages were isolated from wastewater from various cities of Kazakhstan: vB_EcoS_ABO/4, vB_EcoM_PL/4, vB_Eco_CWW/26, vB_EcoM_ShWW/46. Morphological, biological, and genomic analyses showed that the phages belong to different genera of the Caudoviricetes class, possess high lytic activity, broad host range, environmental stability, and lack genes associated with lysogeny, antibiotic resistance, or virulence. Interaction studies with antibiotics revealed synergistic or additive effects in over 75% of cases. These findings highlight the strong potential of the isolated bacteriophages for independent or adjunctive use in the treatment and prevention of colibacillosis in calves. However, further in vivo studies are required to definitively confirm their therapeutic efficacy. Full article

The emergence of multidrug-resistant Salmonella poses a significant threat to global public health and food safety, necessitating the urgent search for new strategies to replace conventional antibiotics. Phages are viruses that can directly target bacteria and have garnered attention in recent years for their development as antibiotic alternatives. In this study, 4458 samples were collected from farms, supermarkets, and human feces, yielding 65 strains of Salmonella, which were serotyped using multiplex PCR. Subsequently, a lytic phage was isolated and identified using the dominant serotype of Salmonella as the host bacterium. We further explored the biological characteristics of this phage through host range, growth properties, and genomic analysis. Finally, we analyzed the potential of the phage to block the cross-host transmission of Salmonella, combining PFGE Salmonella classification, strain sources, and phage lytic phenotypes. The results showed that phage gmqsjt-1 could lyse 69.23% (45/65) of Salmonella, of which 75.56% (34/45) were resistant strains. The optimal multiplicity of infection (MOI) for gmqsjt-1 was 0.01, with a latent period of about 10 min, maintaining high activity within the temperature range of 30 to 60 °C and pH range of 2 to 13. No virulence or resistance genes were detected in the gmqsjt-1 genome, which carries two tail spike proteins (contain FAD binding_2 superfamily, the Tail spike TSP1/Gp66 N-terminal domain, and the Pectin lyase fold) and a holin–lysozyme–spanin lytic system. Phylogenetic classification indicates that phage gmqsjt-1 belongs to a new genus and species of an unnamed family within the class Caudoviricetes. PFGE classification results show a high genetic relationship among human, farm animal, and food source Salmonella, and the comprehensive lytic phenotype reveals that phage gmqsjt-1 can lyse Salmonella with high genetic correlation. These results suggest that this novel lytic Salmonella phage has the potential to inhibit cross-host transmission of Salmonella, making it a promising candidate for developing alternative agents to control Salmonella contamination sources (farms), thereby reducing the risk of human infection with Salmonella through ensuring food system safety. Full article

Acinetobacter baumannii (A. baumannii) is an opportunistic pathogen responsible for a range of severe infections and nosocomial outbreaks. Phage-based therapy and biocontrol represent effective strategies to combat the prevalence of A. baumannii. This study reports a novel phage, BUCT775, capable of specifically lysing A. baumannii, and investigates its physiological properties, genomic characteristics, in vivo therapeutic efficacy, and environmental disinfection performance. Phage BUCT775 is a podovirus that forms clear, well-defined plaques with an average diameter of 2.5 ± 0.52 mm. It exhibits a broad range of temperature stability (4–55 °C) and pH stability (pH 3–12). The optimal multiplicity of infection (MOI) for phage BUCT775 is 0.01. At an MOI of 0.01, it demonstrates a latent period of approximately 10 min and exhibits a high burst size. Genomic sequencing and bioinformatics analysis revealed that phage BUCT775 belongs to the order Caudoviricetes and the family Autographiviridae. Its genome has a G + C content of 39.3% and is not known to contain virulence genes or antibiotic resistance genes. Phage BUCT775 exhibited significant therapeutic effects on A. baumannii-infected G. mellonella larvae, increasing the 120 h survival rate of the larvae by 20%. Additionally, phage BUCT775 efficiently eliminated A. baumannii in the environment, with an average clearance rate exceeding 98% within 3 h. These studies suggest that phage BUCT775 holds significant potential for application in phage therapy and environmental disinfection. Full article

Three novel Aeromonas phages vB_AerVS_332-Yuliya, vB_AerVM_332-Vera, and vB_AerVM_332-Igor and their host Aeromonas veronii CEMTC7594 were found in the same water + sediments sample collected in a freshwater pond. Complete genome sequencing indicated that vB_AerVS_332-Yuliya (43,584 bp) is a siphophage, whereas vB_AerVM_332-Vera (294,685 bp) and vB_AerVM_332-Igor (237,907 bp) are giant phages. The host strain can grow at temperatures from 5 °C to 37 °C with an optimum of 25–37 °C; siphophage vB_AerVS_332-Yuliya effectively reproduced at temperature ≤ 25 °C, the optimal temperature for giant phage vB_AerVM_332-Igor was 25 °C, and giant phage vB_AerVM_332-Vera infected host cells at 5–10 °C. The genomes of these phages differed significantly from known phages; their level of nucleotide identity and values of intergenomic similarity with the corresponding neighboring phages indicated that each of these phages is a member of a new genus/subfamily. Giant phage vB_AerVM_332-Vera is a member of the proposed Chimallinviridae family, which forms Cluster D of giant phages that possibly evolved from phages with shorter genomes. Giant phage vB_AerVM_332-Igor is part of Cluster E, the known members of which preserve the size of genomes. Phages from Cluster F, containing Aeromonas phages among others, show a gradual decrease and/or increase in genomes during evolution, which indicates different strategies for giant phages. Full article

Bacteriophages (phages) are one of the critical biotic drivers of prokaryotic community dynamics, functions, and evolution. Despite their importance in aquatic ecosystems, very few phages have been isolated from freshwater lakes, hampering our understanding of their ecological importance and usage in a variety of biotechnological applications. Limnohabitans, with a ubiquitous distribution, is a metabolically versatile, fast-growing, morphologically diverse freshwater lake bacterial genera. It is especially abundant in pH-neutral and alkaline aquatic habitats, where it represents an average of 12% of freshwater bacterioplankton and plays an important role in funneling carbon from primary producers to higher trophic levels. However, no phages infecting Limnohabitans have been reported to date. Here, we describe, for the first time, three phages infecting Limnohabitans, DC31, DC33, and YIMV22061, isolated from two freshwater lakes in China and characterized using genome content analysis and comparative genomics. DC31 and DC33, recovered from the eutrophic Dianchi Lake, with auxiliary metabolic genes (AMGs), associated with nucleotide metabolism, whereas YIMV22061, isolated from the oligotrophic Fuxian Lake, carried AMGs involved in antibiotic resistance. The AMGs they carried highlight their impacts on Limnohabitans in different environments. Comparative genomic analyses indicate that DC31, DC33, and YIMV22061 represent three novel species in the Caudoviricetes class. IMG/VR database alignment further reveal that these phages are widely distributed across diverse aquatic and terrestrial ecosystems globally, suggesting their ecological significance. This study provides a basis for better understanding Limnohabitans–phage interactions. Full article

Sichuan paocai, a microbial food predominantly fermented by lactic acid bacteria and hosting a complex and diverse microbial ecosystem, serves as an ideal habitat for bacteriophages. However, relatively few studies have been conducted on isolating bacteriophages from fermented vegetables and their application in vegetable fermentation. In this study, three staphylococcal bacteriophages, ΦSx-2, ΦSs-1, and ΦSs-2, were isolated and purified from Sichuan paocai using the spot test method. The morphological features of the phages were characterized using transmission electron microscopy (TEM), while key biological properties such as one-step growth kinetics were systematically evaluated, ultimately verifying their taxonomic placement within the Caudoviricetes class. Furthermore, the potential effects of these phages on the microbial community structure and physicochemical properties during paocai fermentation were investigated using high-throughput sequencing and standard physicochemical assays. Microbial community analysis demonstrated that introducing the phages significantly increased the relative abundance of lactic acid bacteria while reducing the prevalence of spoilage bacteria such as Erwinia, Pantoea, and Enterobacter. Physicochemical assessments revealed that adding phages accelerated the acidification process of paocai, effectively reduced nitrite levels, and increased the concentrations of lactic and acetic acids. Additionally, notable differences in color and flavor were observed between the two groups of paocai during the fermentation process. In summary, the inoculation of bacteriophages ΦSx-2, ΦSs-1, and ΦSs-2 optimized the microbial community structure, enhanced the fermentation process, and improved the quality of Sichuan paocai. Full article

Pseudomonas aeruginosa is a major pathogen associated with hospital-acquired infections, and the spread of carbapenem-resistant isolates highlights the urgency of developing non-conventional therapies, such as phage therapy. For this alternative to be effective, understanding phage–host interactions is crucial for the selection of candidate phages and offers new insights into these dynamics. Background/Objectives: This study aimed to characterize prophage diversity in clinical P. aeruginosa genomes, assess the relationship between phages and the CRISPR/Cas system, and investigate the potential role of prophages in disseminating resistance genes. Methods: A total of 141 genomes from Brazilian hospitals were analyzed. Prophage detection was performed using VIBRANT, and in silico analyses were conducted to evaluate taxonomic diversity, the presence of resistance genes, phage life cycle, genomic distribution, and the presence of the CRISPR/Cas system. Results: A total of 841 viral sequences were identified by the VIBRANT tool, of which 498 were confirmed by CheckV, with a predominance of the class Caudoviricetes and high overall phage diversity. No statistically significant difference was observed in the number of prophages between isolates with and without CRISPR/Cas systems. Prophages carrying resistance genes such as rsmA, OXA-56, SPM-1, and others were detected in isolates harboring the type I-C CRISPR/Cas system. Additionally, prophages showed no preference for specific insertion sites along the bacterial genome. Conclusions: These findings provide evidence of a well-established phage–host relationship. The dual role of prophages—as vectors of antimicrobial resistance and as potential therapeutic agents—reflects their dynamic impact on bacterial communities and reinforces their importance in developing new strategies to combat antimicrobial resistance. Full article

The problem of the multidrug resistance of pathogenic bacteria is a serious concern, one which only becomes more pressing with every year that passes, motivating scientists to look for new therapeutic agents. In this situation, phage therapy, i.e., the use of phages to combat bacterial infections, is back in the spotlight of research interest. Bacterial viruses are highly strain-specific towards their hosts, which makes them particularly valuable for targeting pathogenic variants amidst non-pathogenic microflora, represented by such commensals of animals and humans as E. coli, S. aureus, etc. However, selecting phages for the treatment of bacterial infections is a complex task. The prospective candidates should meet a number of criteria; in particular, the selected phage must not contain potentially dangerous genes (e.g., antibiotic resistance genes, genes of toxins and virulence factors etc.)—or be capable of transferring them from their hosts. This work introduces a new approach to selecting T4-related coliphages; it allows one to identify strains which may be safer in terms of involvement in the horizontal gene transfer. The approach is based on the search for genes that reduce the frequency of genetic transduction. Full article

This study aims to isolate and characterize the lytic phage XC1 targeting Acinetobacter nosocomialis and systematically analyze its biological properties and genomic structure, providing theoretical support for developing novel treatments against antibiotic-resistant infections. Phage XC1 was isolated and purified from lake water. Its morphology, optimal multiplicity of infection (MOI), thermal stability, and pH tolerance were analyzed. Genomic sequencing and functional annotation were performed to identify its lysis-associated genes. Phage XC1 demonstrated a short latent period (20 min) and high burst size (310 plaque-forming units per cell, PFU/cell). It remained stable under temperatures of 50–60 °C and at pH 7, indicating good environmental stability. Genomic analysis revealed a 45,324 bp genome with a GC content of 38.21%, including 84 open reading frames (ORFs), without any lysogenic, virulence, or antibiotic-resistance genes, confirming its safety. Average Nucleotide Identity (ANI) analysis shows that the ANI values between phage XC1 and other phages range from 80% to 95%. As the ANI value between strains of the same species is typically ≥95%, this suggests that phage XC1 may be a previously undiscovered new phage. Classified within the genus Obolenskvirus (class Caudoviricetes), phage XC1 is a virulent bacteriophage with rapid lytic activity and extreme environmental tolerance. Its therapeutic potential against multidrug-resistant infections, either as a monotherapy or in synergy with antibiotics, warrants further investigation. Full article

Bacteriophages are the most numerous, ubiquitous, and diverse biological entities on the planet. Prior studies have identified bacteriophages associated with pathogenic and commensal microbiota of honeybees. In this study we expand on what is known about bacteriophages from the lineages Caudoviricetes, Inoviridae, and Microviridae, which are associated with honeybees (Apidae, Apis mellifera), solitary bees of the genus Nomia (Halictidae, Nomia), and hoverflies (Syrphidae). The complete genomes of seven caudoviruses, seven inoviruses, and 288 microviruses were assembled from honeybees (n = 286) and hoverflies in Arizona (n = 2). We used bacterial host predictive software and sequence read mapping programs to infer the commensal and transient bacterial hosts of pollinating insects. Lastly, this study explores the phylogenetic relationships of microviruses sampled from bees, opportunistically sampled pollinating insects such as hoverflies, and blackflies. Full article

Background/Objectives: This study explores the genome sequencing data from the infection of Pseudomonas fluorescens UFV 041 by the bacteriophage Pijolavirus UFJF_PfSW6, aiming to identify and characterize prophages induced in the host bacterium during the infection. Methods: Scaffolds from sequencing data were analyzed, and reads were mapped to identify potential prophages using phage-to-host coverage metrics. The putative prophage scaffold was annotated, taxonomically classified, and its integration in the host bacterium was verified by PCR amplification of two target genes. We also tested whether mitomycin treatment could induce the prophage to enter the lytic cycle. Results: The prophage UFJF_PfPro was identified with a high phage-to-host coverage ratio. Its genome is 32,700 bp in length, containing 42 genes, 3 terminators, and 11 promoters, with 98.84% completeness. PCR confirmed its integration into P. fluorescens UFV 041, but mitomycin treatment did not induce the lytic cycle. The UFJF_PfPro genome shares 38.60% similarity with the closest lytic phages in the Phitrevirus genus, below genus and species assignment thresholds. A viral proteomic tree clustered UFJF_PfPro with Phitrevirus in a clade representing the Peduoviridae family. Conclusions: The UFJF_PfPro is a prophage integrated into the P. fluorescens UFV 041 genome, but we were unable to induce it to enter the lytic cycle using mitomycin treatment. The genome of UFJF_PfPro encodes all structural proteins typical of the Caudoviricetes class and shares low genomic similarity with species of the genus Phitrevirus, suggesting that UFJF_PfPro represents a new genus and species within the Peduoviridae family. Full article

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. Full article

Salmonella is one of the main foodborne pathogens. Irrational antibiotic management has led to an increase in the incidence of multidrug-resistant strains. Bacteriophages may be an alternative method of food biopreservation and contribute to reducing the number of food poisonings requiring pharmacotherapy. This study aimed to isolate a bacteriophage (phage) targeting indigenous multidrug-resistant (MDR) Salmonella strains, followed by their biological, morphological, and genomic characterization. In this study we isolated Salmonella phage KKP_3822, targeting MDR Salmonella Manchester strain KKP 1213. Salmonella phage KKP_3822 retained high activity in the temperature range from −20 °C to 40 °C and active acidity from pH 3 to 11. Temperatures of 70 °C and 80 °C and extreme pH values (2 and 12) significantly reduced the phage titer. Its activity decreased proportionally to the time of UV exposure. Genome analysis (linear dsDNA with a length of 114,843 bp) revealed the presence of 27 tRNA genes. Proteins encoded by the vB_Sen-IAFB3822 phage were divided into functional modules related to (i) phage structure/assembly, (ii) DNA replication/modification/regulation, (iii) phage lysis, and (iv) DNA packaging into the capsid. No genes associated with antibiotic resistance or integration into the host genome, markers of temperate bacteriophages, were annotated in the Salmonella phage KKP_3822 genome. Based on morphological features and whole-genome sequence analysis, the newly isolated Salmonella phage KKP_3822 shows the greatest similarity to representatives of tailed phages from the Caudoviricetes class, Demerecviridae family, and Epseptimavirus genus. Genome analysis confirmed the virulent nature of the Salmonella phage KKP_3822, making it a potential candidate for food biocontrol. Full article

Bacteriophage (phage) AP1 has been reported to effectively lyse Acidovorax oryzae, the causative agent of bacterial brown stripe in rice. However, phage AP1 exhibits strain-specific lysis patterns. In order to enhance the potential of phages for biological control of rice bacterial brown stripe, this study investigated the possible mechanism of strain-specific infection by characterizing phage AP1 and its susceptible (RS-2) and resistant (RS-1) strains. Based on the current classification standards and available database information, phage AP1 was classified into the class Caudoviricetes, and it is a kind of podophage. Comparative analysis of the susceptible and resistant strains showed no significant differences in growth kinetics, motility, biofilm formation, or effector Hcp production. Interestingly, the resistant strain demonstrated enhanced virulence compared to the susceptible strain. Prokaryotic expression studies indicated that six putative structural proteins of phage AP1 exhibited varying degrees of binding affinity (1.90–9.15%) to lipopolysaccharide (LPS). However, pull-down assays and bacterial two-hybrid analyses revealed that only gp66 can interact with four host proteins, which were identified as glycosyltransferase, RcnB, ClpB, and ImpB through immunoprecipitation and mass spectrometry analyses. The role of LPS in the specific infection mechanism of phage AP1 was further elucidated through the construction of knockout mutant strains and complementary strains targeting a unique gene cluster (wbzB, wbzC, wbzE, and wbzF) involved in LPS precursor biosynthesis. These findings provide novel insights into the mechanisms of phage-host specificity, which are crucial for the effective application of phage AP1 in controlling rice bacterial brown stripe. Full article