Master defence by Søren B Hansen
Master student Søren B Hansen will defend his master thesis:
Analysis of epigenetic variation associated with tenacibaculosis and microbiome composition in Atlantic salmon (Salmo salar).
Host associated microorganisms, its microbiota, affect a variety of host phenotypes, and correspondingly host factors can affect its microbiota. Development in the methods for profiling and analysing biomolecules enables researchers to elucidate the complex interactions between the host and its microbiota. Understanding of these interactions are not only important for basic research questions, but may also have a great applied potential. Aquaculture produces fish for a large part of the world's populations, however, the industry is challenged by occasional disease outbreaks, impairing fish welfare and hindering a more sustainable production. This study builds on a previous finding of strong correlation between the skin ulcer disease tenacibaculosis and the microbiome composition in a cohort of industrial farmed Atlantic salmon (Salmo salar). To investigate host epigenetics as a potential platform for host-microbiome interactions, we characterised and analysed the DNA methylation profile of fish from the cohort. We identified profound DNA methylation differences in fish with tenacibaculosis compared to healthy fish. The difference was evident genome-wide and manifested in many individual differentially methylated sites, frequently aggregated in promoter regions of annotated genes. We identified a potential bias, compromising the conclusions of an often used method to systematically evaluate the attributes of genes containing methylation differences. We found specific genes, located near regions with great methylation differences, involved in processes potentially linked to the disease e.g. heme recycling and feeding behaviour. We utilised a new method for targeted methylation profiling of specific regions, which may be an improvement for future studies. Our results show DNA methylation is linked to tenacibaculosis and suggests that knowledge about epigenetics can expand our understanding of how phenotypes are shaped and can be manipulated.