Inoviridae prophage and bacterial host dynamics during diversification, succession, and Atlantic invasion of Pacific-native Vibrio parahaemolyticus

The epidemiology of Vibrio parahaemolyticus, the leading cause of seafood-borne bacterial gastroenteritis of humans worldwide, dramatically changed in the United States following the establishment of a Pacific-native lineage called sequence type (ST) 36 in the Atlantic. In this study, we used phylogeography based on traceback to environmental source locations and comparative genomics to identify features that promoted evolution, dispersal, and competitive dominance of ST36. The major genomic differentiation and competitive success of ST36 were associated with a striking succession of filamentous prophage in the family Inoviridae (inoviruses), including loss of an inovirus prophage that had been maintained for decades in the endemic north Pacific population. Subsequently, at least five distinct progenitors arising from this diversification translocated from the Pacific into the Atlantic and established four geographically defined clonal subpopulations with remarkably low migration or mixing. Founders of two prevailing Atlantic subpopulations each acquired new stable and diagnostic inoviruses while other subpopulations that apparently declined did not. Broader surveys indicate inoviruses are common and active among the global population of V. parahaemolyticus, and though inovirus replacements, such as in ST36, appear to be infrequent, they are notable in pathogenic lineages that dispersed.