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NAERINGSPH-Nærings-phd

Mechanisms and mode of action for probiotic enhancements in Atlantic salmon.

Alternative title: Virkningsmekanismer bak probiotika til atlantisk laks.

Awarded: NOK 1.8 mill.

Project Number:

322983

Application Type:

Project Period:

2021 - 2024

Funding received from:

Organisation:

Partner countries:

Norway is the biggest producer of Atlantic salmon in the world. One of the main challenges are diseases, which limit the industry growth. In order to control and limit disease outbreaks, new approaches to fish health are needed. The microbiome has a well-known potential to inhibit pathogens but is rarely used in aquaculture. Like all other mucosal surfaces of animals, the skin of Atlantic salmon also has a resident microbial community. This microbiota plays a role in development of host immunity and competes with pathogens for sustenance, which contributes to a healthy host. Recent studies have shown that certain bacterial strains of the Aliivibrio genus have a great potential to increase fish health. Fewer ulcers, increased growth and reduced mortality has been documented after probiotic enhancement with selected Aliivibrio strains. Atlantic salmon exposed to probiotic baths have a significant uptake of bacteria, but little is known about where the bacteria are transported and reside after they reach the circulatory system and how the bacteria and host interact. The mechanisms of these bacteria are still unknown. As are the tissues where they reside execute these effects. The main goal of this thesis is to identify activity and interaction between Atlantic salmon and bacteria in various tissues, both in freshwater and saltwater. The location of bacteria in tissues and how it affects the host are key areas of this thesis. Hence, the first objective of this doctoral thesis is to locate where these bacteria are transported. The second objective is to explore the possible effects of these probiotic Aliivibrio strains in terms of location, effector mechanisms and inate immune function. The third objective is a study on Atlantic salmon exposed to a series of probiotic and pathogenic bacteria where the purpose is to study bacteria-host interaction in the field. Successive methods from objective one and two will be employed and compared to relevant field data. Several infection trials will also be conducted in order to explore the Aliivibrio probiotic specter

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A major challenge in the salmon farming industry is disease and new health managment tools are needed. A good microbiome has a well-known potential to outcompete and inhibit pathogens and represents an untapped potetnial to sustain fish health. Interventions with probiotic bacteria enhance a healthy microbiome balance, but the specific mechanisms of this are still largely unknown. Fish skin constitutes a mechanical barrier, however, it is a mucosal membrane like gut and other mucosal surfaces of other animals and bacterial uptake occurs over intact skin. Like all other mucosal surfaces of animals, the skin of Atlantic salmon has a resident microbial community. This robustness of this microbiota plays a role in development of host immunity and competes with pathogens for sustenance, which contributes to a healthy host. Atlantic salmon given probiotic baths have a significant uptake of bacteria through the skin, but little is known about where the bacteria are transported and reside after they reach the blood and how the bacteria and host interact. This project will identify activity and interaction between Atlantic salmon and bacteria in various tissues in both in freshwater and saltwater. The location and tissue distribution microbiota in wild salmon and farmed salmon will be determined. Host response (gene expression studies and effector cell responses) will be characterized. Atlantic salmon exposed to a series of probiotic and pathogenic bacteria will be studies over all life stages. We will inform on the correlation of host responses microbiota in lab on field studies on and productive measures of probiotic interventons resulting in improved growth, ulcer development, sea lice infection, amoebic gill disease (AGD), and other production data, all of which lead to increased knowledge for the underlying mechanisms of action of probiotics and their increased application for sustainablility in salmon aquacutlure.

Funding scheme:

NAERINGSPH-Nærings-phd