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

Castillo Castillo,Kalatzis Kalatzis,Andersen Andersen,Middelboe Middelboe

doi:10.3390/v11110983

Abstract

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.

Highlights

Temperate phages can integrate into the host chromosome upon infection
Prophages were found in both chromosomes and all the V. anguillarum strains contained at least one prophage-like element with a maximum 12 prophages in one strain (DSM21597) (Figure 1)
In addition to the genetic diversity of the prophages, large differences in host range patterns between genomically identical phages were proliferated in two different V. anguillarum hosts, suggested that phage host range was affected by host-specific, non-genomic mechanisms, which affected phage functional properties, expanding phage diversity beyond genetic variation (Figure 2)

Summary

Introduction

Temperate phages can integrate into the host chromosome upon infection. Here, they become prophages and are replicated along with the rest of the bacterial genome when the cell divides [1].Temperate phages play a major role in the evolution of bacterial communities by transferring genetic information between their bacterial hosts. Temperate phages can integrate into the host chromosome upon infection. They become prophages and are replicated along with the rest of the bacterial genome when the cell divides [1]. Temperate phages play a major role in the evolution of bacterial communities by transferring genetic information between their bacterial hosts. Temperate phages have direct influence on the genetic composition and architecture of the host and potentially enrich the host cell with new beneficial genes (lysogenic conversion), for example by encoding virulence and other fitness factors in pathogenic bacteria [3]. A number of phage-derived bacterial traits (e.g., toxins and gene transfer agents) originate from conserved prophages, which contribute significantly to bacterial evolution [5]

Methods

Results

Discussion

Conclusion