Synergistic effects of commensals and phage predation in suppressing colonization by pathogenic Vibrio parahaemolyticus.

Colonization resistance is a fundamental mechanism by which microbiomes suppress pathogen invasion; however, the ecological and mechanistic determinants of its efficacy remain incompletely understood. Here, we constructed a defined microbial consortium and employed in vivo shrimp infection models to investigate the synergistic interaction between commensal microbes and a pathogen-specific phage in suppressing the pathogen Vibrio parahaemolyticus. Our in vitro experiment revealed that combining key taxa, particularly with phage integration, markedly enhanced pathogen exclusion.

Summary of taxonomy changes ratified by the International Committee on Taxonomy of Viruses (ICTV) from the Bacterial Viruses Subcommittee, 2025.

This article summarises the activities of the International Committee on Taxonomy of Viruses Bacterial Viruses Subcommittee, detailing developments in the classification of bacterial viruses. We provide here an overview of all new, abolished, moved and renamed taxa proposed in 2024, approved by the Executive Committee, and ratified by membership vote in 2025. Through the collective efforts of 74 international contributors of taxonomy proposals in this round, 43 ratified proposals have led to the creation of one new phylum, one class, four orders, 33 families, 14 subfamilies, 194 genera and 995 species.

Distinct effects of mucin on phage-host interactions in model systems of beneficial and pathogenic bacteria.

Phage-host interactions that occur in host-associated microbiomes are influenced by a plethora of environmental factors. Mucins are glycoproteins that represent the main component of mucus, which is found in the animal digestive tract and on the surface of certain organs, serving as the first line of defense against toxins and pathogens. Previous studies have shown that lytic phages have an important influence on the microbial composition in mucosal areas.

Prophage-encoded chitinase gene supports growth of its bacterial host isolated from deep-sea sediments.

Auxiliary metabolic genes encoded by bacteriophages can influence host metabolic function during infection. In temperate phages, auxiliary metabolic genes (AMGs) may increase host fitness when integrated as prophages into the host genome. However, little is known about the contribution of prophage-encoded AMGs to host metabolic properties.

Diversification of Biofilm Populations under Repeated Phage Exposures Decreases the Efficacy of the Treatment.

Phage therapy has been proposed as a therapeutic alternative to antibiotics for the treatment of chronic, biofilm-related infections. To gain a deeper insight into the complex biofilm-phage interactions, we investigated in the present study the effect of three successive exposures to lytic phages of biofilms formed by the reference strains PAO1 and PA14 as well as of two sequential clinical isolates from the sputum of a patient with cystic fibrosis (CF). The Calgary device was employed as a biofilm model and the efficacy of phage treatment was evaluated by measurements of the biomass stained with crystal violet (CV) and of the cell density of the biofilm bacterial population (CFU/mL) after each of the three phage exposures.

Evolution of Specific Phages Infecting the Fish Pathogen .

Background: is the causative agent of the bacterial cold-water disease and rainbow trout fry syndrome. Owing to the issues associated with increasing use of antibiotics to control the diseases, phage therapy has been proposed as an alternative method to control infection within the industry.

Materials And Methods: We explored two simple and fast strategies for the isolation of evolved phages, using three well-characterized phages FpV4, FpV9, and FPSV-S20.

Strain-specific quorum-sensing responses determine virulence properties in Vibrio anguillarum.

Bacterial populations communicate using quorum-sensing (QS) molecules and switch on QS regulation to engage in coordinated behaviour such as biofilm formation or virulence. The marine fish pathogen Vibrio anguillarum harbours several QS systems, and our understanding of its QS regulation is still fragmentary. Here, we identify the VanT-QS regulon and explore the diversity and trajectory of traits under QS regulation in Vibrio anguillarum through comparative transcriptomics of two wildtype strains and their corresponding mutants artificially locked in QS-on (ΔvanO) or QS-off (ΔvanT) states.

Reversible mutations in gliding motility and virulence genes: A flexible and efficient phage defence mechanism in Flavobacterium psychrophilum.

Flavobacteria are among the most important pathogens in freshwater salmonid aquaculture worldwide. Due to concerns regarding development of antibiotic resistance, phage therapy has been proposed as a solution to decrease pathogen load. However, application of phages is challenged by the development of phage resistance, and knowledge of the mechanisms and implications of phage resistance is therefore required.

The Gut Microbiota of Healthy and -Infected Rainbow Trout Fry Is Shaped by Antibiotics and Phage Therapies.

In the aquaculture sector, there is an increased interest in developing environmentally friendly alternatives to antibiotics in the treatment and prevention of bacterial infections. This requires an understanding of the effects of different treatments on the fish microbiota as a measure for improving the fish health status. In this study, we focused on the freshwater pathogen and investigated the effects of antibiotics (florfenicol) and phage therapies on the gut microbiota of healthy and infected rainbow trout fry (1-2 g).

Prevalence of genetically similar Flavobacterium columnare phages across aquaculture environments reveals a strong potential for pathogen control.

Intensive aquaculture conditions expose fish to bacterial infections, leading to significant financial losses, extensive antibiotic use and risk of antibiotic resistance in target bacteria. Flavobacterium columnare causes columnaris disease in aquaculture worldwide. To develop a bacteriophage-based control of columnaris disease, we isolated and characterized 126 F.

Interactions between the Prophage 919TP and Its Host: Implications of Mutation for Phage Resistance, Cell Auto-Aggregation, and Motility.

Prophage 919TP is widely distributed among and is induced to produce free φ919TP phage particles. However, the interactions between prophage φ919TP, the induced phage particle, and its host remain unknown. In particular, phage resistance mechanisms and potential fitness trade-offs, resulting from phage resistance, are unresolved.

Comparison of Delivery Methods in Phage Therapy against Infections in Rainbow Trout.

Viruses of bacteria, bacteriophages, specifically infect their bacterial hosts with minimal effects on the surrounding microbiota. They have the potential to be used in the prevention and treatment of bacterial infections, including in the field of food production. In aquaculture settings, disease-causing bacteria are often transmitted through the water body, providing several applications for phage-based targeting of pathogens, in the rearing environment, and in the fish.

Genomic Analysis of Provides Insight on Its Virulence Factors and Phylogeny and Highlights the Potential of Reverse Vaccinology in Aquaculture.

Pasteurellosis in farmed lumpsuckers, , has emerged as a serious disease in Norwegian aquaculture in recent years. Genomic characterization of the causative agent is essential in understanding the biology of the bacteria involved and in devising an efficient preventive strategy. The genomes of two clinical isolates were sequenced (≈2.

Dynamics of Baltic Sea phages driven by environmental changes.

Phage predation constitutes a major mortality factor for bacteria in aquatic ecosystems, and thus, directly impacts nutrient cycling and microbial community dynamics. Yet, the population dynamics of specific phages across time scales from days to months remain largely unexplored, which limits our understanding of their influence on microbial succession. To investigate temporal changes in diversity and abundance of phages infecting particular host strains, we isolated 121 phage strains that infected three bacterial hosts during a Baltic Sea mesocosm experiment.

Bacteriophage Resistance Affects Flavobacterium columnare Virulence Partly via Mutations in Genes Related to Gliding Motility and the Type IX Secretion System.

Increasing problems with antibiotic resistance have directed interest toward phage therapy in the aquaculture industry. However, phage resistance evolving in target bacteria is considered a challenge. To investigate how phage resistance influences the fish pathogen Flavobacterium columnare, two wild-type bacterial isolates, FCO-F2 and FCO-F9, were exposed to phages (FCO-F2 to FCOV-F2, FCOV-F5, and FCOV-F25, and FCO-F9 to FCL-2, FCOV-F13, and FCOV-F45), and resulting phenotypic and genetic changes in bacteria were analyzed.

Genome-informed approach to identify genetic determinants of Flavobacterium psychrophilum phage susceptibility.

The fish pathogen Flavobacterium psychrophilum infects farmed salmonids worldwide, and application of bacteriophages has been suggested for controlling disease outbreaks in aquaculture. Successful application of phages requires detailed knowledge about the variability in phage susceptibility of the host communities. In this study, we analysed the genetic diversity of F.

Interactions between Rainbow Trout Eyed Eggs and spp. Using a Bath Challenge Model: Preliminary Evaluation of Bacteriophages as Pathogen Control Agents.

The microbial community surrounding fish eyed eggs can harbor pathogenic bacteria. In this study we focused on rainbow trout () eyed eggs and the potential of bacteriophages against the pathogenic bacteria and . An infection bath method was first established, and the effects of singular phages on fish eggs was assessed (survival of eyed eggs, interaction of phages with eyed eggs).

Phage-Mediated Control of in Aquaculture: Experiments to Compare Delivery Methods.

Phage-based approaches have gained increasing interest as sustainable alternative strategies to antibiotic treatment or as prophylactic measures against disease outbreaks in aquaculture. The potential of three methods (oral, bath, and injection) for delivering a two-component phage mixture to rainbow trout fry for controlling infections and reduce fish mortality was investigated using bacteriophages FpV4 and FPSV-D22. For the oral administration experiment, bacteriophages were applied on feed pellets by spraying (1.

Bacteriophages as Biocontrol Agents for Biofilms and Rainbow Trout Infections.

Bacteriophages (phages) have been proposed as an alternative to antibiotics and surface disinfectants for treatment of biofilms and fish infections in aquaculture settings. The aim of the study was to estimate the minimal phage:host ratio (PHR) required for the control of biofilm formation and mortalities caused by in experimentally infected fish. cells in different stages of biofilm formation were exposed to the lytic phage FPSV-D22 at different PHRs.

Beyond Cholera: Characterization of -Encoding Filamentous Phages in the Marine Fish Pathogen .

Zonula occludens toxin (Zot) is a conserved protein in filamentous vibriophages and has been reported as a putative toxin in . Recently, widespread distribution of encoding prophages was found among marine species, including environmental isolates. However, little is known about the dynamics of these prophages beyond .

High cell densities favor lysogeny: induction of an H20 prophage is repressed by quorum sensing and enhances biofilm formation in Vibrio anguillarum.

Temperate ϕH20-like phages are repeatedly identified at geographically distinct areas as free phage particles or as prophages of the fish pathogen Vibrio anguillarum. We studied mutants of a lysogenic isolate of V. anguillarum locked in the quorum-sensing regulatory modes of low (ΔvanT) and high (ΔvanO) cell densities by in-frame deletion of key regulators of the quorum-sensing pathway.