Abstract
Bacteriophages or phages—viruses of bacteria—are abundant and considered to be highly diverse. Interestingly, a particular group of lytic Vibrio cholerae–specific phages (vibriophages) of the International Centre for Diarrheal Disease Research, Bangladesh cholera phage 1 (ICP1) lineage show high levels of genome conservation over large spans of time and geography, despite a constant coevolutionary arms race with their host. From a collection of 67 sequenced ICP1 isolates, mostly from clinical samples, we find these phages have mosaic genomes consisting of large, conserved modules disrupted by variable sequences that likely evolve mostly through mobile endonuclease-mediated recombination during coinfection. Several variable regions have been associated with adaptations against antiphage elements in V. cholerae; notably, this includes ICP1’s CRISPR-Cas system. The ongoing association of ICP1 and V. cholerae in cholera-endemic regions makes this system a rich source for discovery of novel defense and counterdefense strategies in bacteria-phage conflicts in nature.
Highlights
As a waterborne pathogen and causative agent of the infectious diarrheal disease cholera, Vibrio cholerae must persist in aquatic reservoirs and flourish in the human gut
This review focuses on one such lytic phage, International Centre for Diarrheal Disease Research, Bangladesh cholera phage 1 (ICP1), which has emerged as a persistent and pervasive phage shaping the evolution of epidemic V. cholerae (Figure 1)
Substantial progress has been made in characterizing ICP1, and these efforts have uncovered some fascinating features of this lytic phage, yet much remains unknown
Summary
As a waterborne pathogen and causative agent of the infectious diarrheal disease cholera, Vibrio cholerae must persist in aquatic reservoirs and flourish in the human gut. This review focuses on one such lytic phage, International Centre for Diarrheal Disease Research, Bangladesh cholera phage 1 (ICP1), which has emerged as a persistent and pervasive phage shaping the evolution of epidemic V. cholerae (Figure 1). Robust replication of toxigenic V. cholerae results in shedding of the pathogen in stool This reseeds the aquatic environment and leads to transmission of disease from person to person via fecal-oral contamination and contributes to the explosive nature of cholera outbreaks (7). International Centre for Diarrheal Disease Research, Bangladesh cholera phage 1 (ICP1) and epidemic Vibrio cholerae coexist and persist in nature. Counteradaptations in the phage lead to selection of new ICP1 variants (light teal) This reciprocal coevolution continues (emergence of dark gray bacteria) in the aquatic and intestinal environments.
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