Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8395
Title: Genomic evidence of adaptive evolution in emergent Vibrio parahaemolyticus ecotypes
Author: Jeffrey W. Turner, Chris T. Berthiaume, Rhonda Morales, E. Virginia Armbrust, Mark S. Strom
Publication Year: 2016
Journal: Elementa: Science of the Anthropocene
Volume: 4
Pages: 000117
DOI: 10.12952/journal.elementa.000117
Keywords: vibrio parahaemolyticus, adaptation, evolution,

The ubiquitous marine bacterium Vibrio parahaemolyticus is a leading cause of illness associated with seafood consumption. The emergence of two genetically distinct ecotypes (ST3 and ST36) has led to an alarming increase in the size and frequency of disease outbreaks. We conducted a genomic comparison of 30 V. parahaemolyticus genomes that represent a diverse collection of 15 genetically distinct ecotypes, including newly sequenced representatives of ST3 and ST36, isolated from both clinical and environmental sources. A multistep evolutionary analysis showed that genes associated with sensing and responding to environmental stimuli have evolved under positive selection, identifying examples of convergent evolution between ST3 and ST36. A comparison of predicted proteomes indicated that ST3 and ST36 ecotypes laterally acquired tens of novel genes associated with a variety of functions including dormancy, homeostasis and membrane transport. Genes identified in this study play an apparent role in environmental fitness and may confer cross protection against stressors encountered in the human host. Together, these results show the evolution of stress response is an important genetic mechanism correlated with the recent emergence of the ST3 and ST36 ecotypes.


Given that V. parahaemolyticus is an environmental bacterium and the human host is an alternate and novel ecological niche, we hypothesized that the evolution of dual-purpose genes, integral to both environmental fitness and human pathogenesis, would correlate with the recent emergence of the ST3 and ST36 ecotypes. To test this hypothesis, we conducted a genomic analysis of 30 V. parahaemolyticus genomes to identify the evolutionary forces correlated with clinically predominant ecotypes (ST3 and ST36). We dissected two mechanisms of adaptive evolution: the mutation of genes comprising the core genome and the lateral acquisition of genes comprising the accessory genome. 

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Theme: Sustainable, safe and secure seafood for healthy populations and vibrant communities
Foci: Provide scientific support to ensure safe seafood for healthy populations and characterize how human activities and climate affect risks from pathogens, chemical contaminants and biotoxins