Use of Bacteriophages to Control Vibrio Contamination of Microalgae Used as a Food Source for Oyster Larvae During Hatchery Culture

Isolation and characterization of a novel bacteriophage ST1749 and its effectiveness against Vibrio parahaemolyticus and Salmonella spp

Bacteriophages are extensively employed across various fields, including medicine, veterinary medicine, the food industry, agriculture, biotechnology, and pharmacy, owing to their numerous advantages. These advantages include rapid clearance of pathogens, self-propagation at the infection site, host specificity, potential for genetic modification, ease of isolation, stability, and low production costs. This study isolated a bacteriophage from shrimp pond wastewater in the Mekong Delta region. The bacteriophage was identified as a lytic bacteriophage belonging to the genus Bruyoghevirus, class Caudoviricetes, with the ability to effectively lyse three bacterial strains: V. parahaemolyticus, Salmonella enteritidis, and Salmonella typhimurium. Growth curve analysis revealed variations in the latency period and the number of phages produced during the life cycle across all three hosts. Bacteriophage Produced 117, 176, and 52 PFU/cell against V. parahaemolyticus, S. enteritidis, and S. typhimurium, respectively. Phage ST1749 demonstrated activity across a broad range of temperatures (-20 °C to 70 °C) and pH levels (2 to 10), with optimal stability observed at pH 5 to 7. Furthermore, phage ST1749 exhibited biofilm-degrading and lytic capabilities against the three bacterial strains studied. These findings suggest that phage ST1749 has the potential to serve as a biocontrol agent for treating infections caused by antibiotic-resistant bacteria.

Bacteriophage Therapy in Freshwater and Saltwater Aquaculture Species

Bacteriophages, or phages, which are viruses with specifically restricted tropism for bacteria, have regained interest in the last few decades as alternative therapeutic agents against antibiotic-resistant pathogenic bacteria in animals and humans worldwide. In this context, bacteriophage therapy has been developed to treat bacterial infections of cultured fish, shellfish, and crustaceans. Nowadays, aquaculture is the only feasible solution to meet the continuously growing global demand for high-quality seafood. As such, it is crucial to focus on controlling the spread of pathogenic bacteria, as they have a significant economic impact on aquaculture systems. Overall, the documented research supports the application of bacteriophage therapy in aquaculture, but also underlies the need for additional studies, as it is still mostly in the scientific stage. This review aims to highlight and critically examine recent advancements in the application of bacteriophages to treat the most common bacterial infectious diseases in both freshwater and saltwater aquaculture species, providing topical perspectives and innovative advances.

Taxonomic diversity and functional potential of microbial communities in oyster calcifying fluid

Creating and maintaining an appropriate chemical environment is essential for biomineralization, the process by which organisms precipitate minerals to form their shells or skeletons, yet the mechanisms involved in maintaining calcifying fluid chemistry are not fully defined. In particular, the role of microorganisms in facilitating or hindering animal biomineralization is poorly understood. Here, we investigated the taxonomic diversity and functional potential of microbial communities inhabiting oyster calcifying fluid. We used shotgun metagenomics to survey calcifying fluid microbial communities from three different oyster harvesting sites. There was a striking consistency in taxonomic composition across the three collection sites. We also observed archaea and viruses that had not been previously identified in oyster calcifying fluid. Furthermore, we identified microbial energy-conserving metabolisms that could influence the host's calcification, including genes involved in sulfate reduction and denitrification that are thought to play pivotal roles in inorganic carbon chemistry and calcification in microbial biofilms. These findings provide new insights into the taxonomy and functional capacity of oyster calcifying fluid microbiomes, highlighting their potential contributions to shell biomineralization, and contribute to a deeper understanding of the interplay between microbial ecology and biogeochemistry that could potentially bolster oyster calcification.

IMPORTANCE

Previous research has underscored the influence of microbial metabolisms in carbonate deposition throughout the geological record. Despite the ecological importance of microbes to animals and inorganic carbon transformations, there have been limited studies characterizing the potential role of microbiomes in calcification by animals such as bivalves. Here, we use metagenomics to investigate the taxonomic diversity and functional potential of microbial communities in calcifying fluids from oysters collected at three different locations. We show a diverse microbial community that includes bacteria, archaea, and viruses, and we discuss their functional potential to influence calcifying fluid chemistry via reactions like sulfate reduction and denitrification. We also report the presence of carbonic anhydrase and urease, both of which are critical in microbial biofilm calcification. Our findings have broader implications in understanding what regulates calcifying fluid chemistry and consequentially the resilience of calcifying organisms to 21st century acidifying oceans.

Interactions of Vibrio phages and their hosts in aquatic environments

Bacteriophages (phages) are viruses that specifically infect bacteria. These viruses were discovered a century ago and have been used as a model system in microbial genetics and molecular biology. In order to survive, bacteria have to quickly adapt to phage challenges in their natural settings. In turn, phages continuously develop/evolve mechanisms for battling host defenses. A deeper understanding of the arms race between bacteria and phages is essential for the rational design of phage-based prophylaxis and therapies to prevent and treat bacterial infections. Vibrio species and their phages (vibriophages) are a suitable model to study these interactions. Phages are highly ubiquitous in aquatic environments and Vibrio are waterborne bacteria that must survive the constant attack by phages for successful transmission to their hosts. Here, we review relevant literature from the past two years to delve into the molecular interactions of Vibrio species and their phages in aquatic niches.

Role of Bacteriophages in the Evolution of Pathogenic Vibrios and Lessons for Phage Therapy

Viruses of bacteria, i.e., bacteriophages (or phages for short), were discovered over a century ago and have played a major role as a model system for the establishment of the fields of microbial genetics and molecular biology. Despite the relative simplicity of phages, microbiologists are continually discovering new aspects of their biology including mechanisms for battling host defenses. In turn, novel mechanisms of host defense against phages are being discovered at a rapid clip. A deeper understanding of the arms race between bacteria and phages will continue to reveal novel molecular mechanisms and will be important for the rational design of phage-based prophylaxis and therapies to prevent and treat bacterial infections, respectively. Here we delve into the molecular interactions of Vibrio species and phages.

Novel RNA viruses in oysters revealed by virome

Eighteen novel RNA viruses were found in Crassostrea hongkongensis. Phylogenic analysis shows evidence of recombination between major genes of viruses. Picobirnaviruses are ubiquitous and abundant in oysters.

Isolation and Characterization of a Lytic Vibrio parahaemolyticus Phage vB_VpaP_GHSM17 from Sewage Samples

Vibrio parahaemolyticus is a major foodborne pathogen and the main cause of diarrheal diseases transmitted by seafood such as fish, shrimp, and shellfish. In the current study, a novel lytic phage infecting V. parahaemolyticus, vB_VpaP_GHSM17, was isolated from the sewage of a seafood market, Huangsha, Guangzhou, and its morphology, biochemistry, and taxonomy features were identified. Morphological observation revealed that GHSM17 had an icosahedral head with a short, non-contractile tail. The double-stranded DNA genome of GHSM17 consisted of 43,228 bp with a GC content of 49.42%. In total, 45 putative ORFs were identified in the GHSM17 genome. Taxonomic analysis indicated GHSM17 belonging to genus Maculvirus, family Autographiviridae. In addition, GHSM17 was stable over a wide range of temperatures (20-60 °C) and pH (5-11) and was completely inactivated after 70 min of ultraviolet irradiation. The bacterial inhibition assay revealed that GHSM17 could inhibit the growth of V. parahaemolyticus within 8 h. The results support that phage GHSM17 may be a potential candidate in the biological control of V. parahaemolyticus contamination in aquaculture.

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.

Isolation and Characterization of Six Vibrio parahaemolyticus Lytic Bacteriophages From Seafood Samples

Vibrio parahaemolyticus is a foodborne pathogen that is frequently isolated from a variety of seafood. To control this pathogenic Vibrio spp., the implementation of bacteriophages in aquaculture and food industries have shown a promising alternative to antibiotics. In this study, six bacteriophages isolated from the seafood samples demonstrated a narrow host range specificity that infecting only the V. parahaemolyticus strains. Morphological analysis revealed that bacteriophages Vp33, Vp22, Vp21, and Vp02 belong to the Podoviridae family, while bacteriophages Vp08 and Vp11 were categorized into the Siphoviridae family. All bacteriophages were composed of DNA genome and showed distinctive restriction fragment length polymorphism. The optimal MOI for bacteriophage propagation was determined to be 0.001 to 1. One-step growth curve revealed that the latent period ranged from 10 to 20 min, and the burst size of bacteriophage was approximately 17 to 51 PFU/cell. The influence of temperature and pH levels on the stability of bacteriophages showed that all bacteriophages were optimally stable over a wide range of temperatures and pH levels. In vitro lytic activity of all bacteriophages demonstrated to have a significant effect against V. parahaemolyticus. Besides, the application of a bacteriophage cocktail instead of a single bacteriophage suspension was observed to have a better efficiency to control the growth of V. parahaemolyticus. Results from this study provided a basic understanding of the physiological and biological properties of the isolated bacteriophages before it can be readily used as a biocontrol agent against the growth of V. parahaemolyticus.

Use of bacteriophage vB_Pd_PDCC-1 as biological control agent of Photobacterium damselae subsp. damselae during hatching of longfin yellowtail (Seriola rivoliana) eggs

AIMS

This study describes the effect of phage therapy on hatching of longfin yellowtail (Seriola rivoliana) eggs challenged with Photobacterium damselae subsp. damselae.

METHODS AND RESULTS

A lytic phage (vB_Pd_PDCC-1) against P. damselae subsp. damselae was isolated and characterized. The use of phage vB_Pd_PDCC-1 increased the hatching rate of eggs, and reduced presumptive Vibrio species to non-detectable numbers, even in non-disinfected eggs. High-throughput 16S rRNA gene sequencing analysis revealed that phage vB_Pd_PDCC-1 caused significant changes in the composition and structure of the associated microbiota, allowing that members (e.g. those belonging to the family Vibrionaceae) of the class Gammaproteobacteria to be displaced by members of the class Alphaproteobacteria.

CONCLUSIONS

To the best of our knowledge, this represents the first study evaluating phage therapy to control potential negative effects of P. damselae subsp. damselae during hatching of longfin yellowtail eggs.

SIGNIFICANCE AND IMPACT OF THE STUDY

The Seriola genus includes several important commercial fish species due to its rapid growth and easy adaptability to confinement conditions. However, bacterial infections (especially those caused by Vibrio and Photobacterium species) are among the main limiting factors for the intensification of marine fish aquaculture, particularly during early development stages. Therefore, the use of phages, which are natural killers of bacteria, represents a promising strategy to reduce the mortality of farmed organisms caused by pathogenic bacteria.