Occurrence and functional consequence of a novel prophage linked to non-pathogenic conversion in pandemic O3:K6 Vibrio parahaemolyticus - Over the past two decades, the number of Vibrio parahaemolyticus infections worldwide has increased
dramatically. In the United States (U.S.), V. parahaemolyticus has emerged as the leading cause of seafood-
borne gastroenteritis. A majority of these illnesses have been attributed to the appearance and expansion of a
pandemic serotype (O3:K6). However, in the Pacific Northwest (PNW) region of the U.S., this highly virulent
serotype is very rarely associated with outbreaks (with only three reported cases), despite its alarming
abundance in the environment. Although no explanation for this curious etiology has materialized we have
previously shown that environmental O3:K6 from this region exhibited decreased virulence in zebrafish.
Subsequent genome sequencing has revealed that environmental O3:K6 from the PNW carry a novel
prophage (Vibrio prophage NW1) that has displaced seven genes: VP1884-VP1890. To better understand
pandemic V. parahaemolyticus dynamics we propose to investigate the genetic mechanisms that underlie the
unique etiology of this pathogen in the PNW. Our central hypothesis is that prophage NW1 depresses
virulence through the displacement of 7 genes including the cold-shock transcriptional regulator cspA
(VP1889), the virulence-associated vacB (VP1890), and the hypothetical protein VP1888. The recent dramatic
increase in the number of V. parahaemolyticus infections, the continued expansion of the range and seasonal
window of infections (owing to climate warming), and the increasing reliance of the global population on
seafood as a major source of animal protein all provide strong rationale for this study. The long-term goal of
our research is to understand how prophage NW1 affects the virulence of pandemic V. parahaemolyticus
O3:K6. To accomplish this goal, the investigators will address three specific aims using a combination of
traditional and cutting-edge approaches: 1) screen a large collection of environmental isolates, including O3:K6
isolates, to determine the prevalence of prophage NW1, 2) quantify the virulence of O3:K6 isolates carrying
prophage NW1 by intraperitoneal challenge in zebrafish and 3) investigate the mechanisms underpinning
virulence by quantifying virulence in wild-type and prophage mutants. Results are expected to answer open
questions about virulence and evolution in a pandemic bacterial pathogen that poses a significant threat to
human health and food security. This study aligns closely with the NIAID mandate to respond to emerging
public health threats as well as the NIAID mission to better understand, treat and ultimately prevent infectious
diseases. Further, this study aligns closely with the goals of the AREA program in that it will strengthen the
research environment at a minority-serving institution and expose underrepresented students to meritorious
research.
