Developing novel models to understand threats from Vibrio pathogens for safeguarding aquatic food supply under future climates

Climate change, leading to ocean warming, is affecting the frequency, intensity and duration of extreme weather events affecting nearshore ecosystems that will make our UK coastal shellfisheries more vulnerable to new and emerging microbial diseases, and with potentially greater associated human health concerns. When bacteria encounter extreme or unfavourable environmental conditions they enter a state of dormancy to protect themselves, however, they can re-awaken when favourable environmental conditions return. For bacterial pathogens these re-emergent blooms can be hazardous to the environment and in some cases to human health. A major problem in the prevention of bacterial diseases is that dormant cells are not detectable by routine tests making them difficult to study. In this project, we will exploit new approaches to understand the ways (mechanisms) by which dormant bacterial Vibrio cells (our study organism) emerge as active disease-causing pathogens in the environment to provide a springboard for future projects for predicting and preventing Vibrio disease establishment in wild shellfisheries and farmed shellfish, and the protection of human health.

Vibriosis is a disease responsible for numerous mass mortality events in managed and wild shellfisheries, and globally Vibrio pathogens are the leading causes of seafood related gastroenteritis in humans. In our coastal waters, sediment and shellfish, Vibrio parahaemolyticus is found during the summer months but is not detected in the winter. It had been assumed that these bacteria die due to the cold-water temperatures, however, we know now that a small proportion enter dormancy in order to survive cooler (winter) conditions. When summer conditions return and, nutrient levels and sea temperatures increase these dormant cells reawaken, growing into bacterial populations that can infect shellfish and cause adverse human health impacts.

In this project, we will first detect and quantify Vibrio in its various functional states in relation to environmental abiotic factors in water, sediment, and shellfish from a coastal site in Dorset, England. The cell sorting and staining methods we will apply, will allow us to separate dormant Vibrio cell populations from those that are metabolically active and those that are non-viable. We will then assess the ability to resuscitate the dormant cells collected from the environmental samples through manipulating the salt and temperature to simulate summer conditions and with the addition of sodium lactate (we have shown that lactate can resuscitate Vibrio dormant cells for our laboratory induced dormant cells). We will also test the virulence potential of the resuscitated Vibrio cells derived from our environmental samples through their injection to an established moth larvae disease model. Finally, we will develop analytical protocols (using mass spectrophotometry methods) to determine the fate of lactate in environmental dormant cells and identify metabolism mechanisms as the dormant cells switch to the actively growing cell population.

Collectively these studies will be a major step forward in establishing the factors that allow Vibrio cells to emerge from dormancy and establish as a growing population under favourable climate conditions to cause disease. Improving our ability to predict when Vibrio bacterial populations are established will help prevent disease reinfections and avoidance of seasonal epidemics through adoption of mitigation strategies such as depuration of the shellfish, and/or early and/or selective harvesting.