Structure of anguibactin, a unique plasmid-related bacterial siderophore from the fish pathogen Vibrio anguillarum

ABSTRACT To study the possible use of probiotics in fish farming, we evaluated the in vitro and in vivo antagonism of antibacterial strainPseudomonas fluorescens strain AH2 against the fish-pathogenic bacterium Vibrio anguillarum. As iron is important in virulence and bacterial interactions, the effect ofP. fluorescens AH2 was studied under iron-rich and iron-limited conditions. Sterile-filtered culture supernatants from iron-limited P. fluorescens AH2 inhibited the growth ofV. anguillarum, whereas sterile-filtered supernatants from iron-replete cultures of P. fluorescens AH2 did not.P. fluorescens AH2 inhibited the growth of V. anguillarum during coculture, independently of the iron concentration, when the initial count of the antagonist was 100 to 1,000 times greater that of the fish pathogen. These in vitro results were successfully repeated in vivo. A probiotic effect in vivo was tested by exposing rainbow trout (Oncorynchus mykissWalbaum) to P. fluorescens AH2 at a density of 105 CFU/ml for 5 days before a challenge with V. anguillarum at 104 to 105 CFU/ml for 1 h. Some fish were also exposed to P. fluorescens AH2 at 107 CFU/ml during the 1-h infection. The combined probiotic treatment resulted in a 46% reduction of calculated accumulated mortality; accumulated mortality was 25% after 7 days at 12°C in the probiotic-treated fish, whereas mortality was 47% in fish not treated with the probiont.

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Large Phenotypic and Genetic Diversity of Prophages Induced from the Fish Pathogen Vibrio anguillarum

Viruses ◽

10.3390/v11110983 ◽

2019 ◽

Vol 11 (11) ◽

pp. 983 ◽

Cited By ~ 2

Author(s):

Castillo ◽

Andersen ◽

Kalatzis ◽

Middelboe

Keyword(s):

Vibrio Anguillarum ◽

Fish Pathogen ◽

Pcr Assay ◽

Phenotypic Properties ◽

Specific Element ◽

Group Iii ◽

Multiplex Pcr Assay ◽

Prophage Sequence ◽

Fish And Shellfish ◽

Efficient Transfer

Vibrio anguillarum is a marine pathogenic bacterium that causes vibriosis in fish and shellfish. Although prophage-like sequences have been predicted in V. anguillarum strains, many are not characterized, and it is not known if they retain the functional capacity to form infectious particles that can infect and lysogenize other bacterial hosts. In this study, the genome sequences of 28 V. anguillarum strains revealed 55 different prophage-related elements. Chemical and spontaneous induction allowed a collection of 42 phage isolates, which were classified in seven different groups according to a multiplex PCR assay. One shared prophage sequence, p41 (group III), was present in 17 V. anguillarum strains, suggesting that this specific element is very dynamically exchanged among V. anguillarum populations. Interestingly, the host range of genetically identical phages was highly dependent on the strains used for proliferation, indicating that phenotypic properties of phages were partly regulated by the host. Finally, experimental evidence displayed that the induced phage ɸVa_90-11-287_p41 was able to lysogenize V. anguillarum strain Ba35, and subsequently spontaneously become released from the lysogenized cells, demonstrating an efficient transfer of the phage among V. anguillarum strains. Altogether, the results showed large genetic and functional diversity and broad distribution of prophages in V. anguillarum, and demonstrated the potential of prophages as drivers of evolution in V. anguillarum strains.

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