Master of Science Typhaine Le Doujet will Friday October 31st, 2025, at 10:00 hold her Thesis Defense for the PhD degree in Science. The title of the thesis is:
« The intestinal microbiome of the Northeast Arctic Cod (Gadus morhua) »
The Northeast Arctic cod, also known as the migrating Atlantic cod or "skrei," is one of the most important fish species in the world. Every year, these extraordinary fish swim more than one thousand kilometers from the cold waters of the Barents Sea to the Norwegian coast to lay their eggs. Their long journey, large size, and vital role in the marine food web make them especially interesting to scientists.
In this study, we explored the bacteria living inside the intestines of cod to understand who they are and what they do. These microscopic organisms play important roles in the fish’s health by aiding in food digestion, nutrient absorption, and protection against harmful microbes. Understanding these microbes not only benefits the fish but also offers practical applications, such as improving fish farming practices, promoting healthier oceans, and discovering new products for human use, including medicines and food preservatives.
Overall, we found that the gut of cod hosted two distinct bacterial communities. The first, found in the feces, was dominated by a single group of bacteria called Photobacterium, which was present in all the fish studied. The second, found in the mucus lining of the intestinal wall, was much more diverse and varied between individual fish. Depending on the fish, the dominant bacteria included Pseudomonas, Photobacterium, or Escherichia-related strains.
One particularly exciting discovery was the presence of proteins capable of functioning at icy cold temperatures, which hold potential applications in various sectors, including the food industry, pharmaceuticals, medicine, and waste management. This is because such proteins can operate efficiently in cold environments, reducing the need for energy-intensive heating processes, thereby lowering costs and minimizing environmental impact.
In this study, we identified 57 chitinases in the feces of six cod. Chitinases are enzymes that break down chitin, a tough material found in the exoskeletons of shellfish such as shrimp and crabs. These enzymes degrade chitin into valuable compounds that have applications in the food industry, medicine, and environmental cleanup. Moreover, the chitinases found in the gut of cod are particularly interesting because they are expected to function at low temperatures, as the intestines of cod are in direct contact with the cold environment.
To test the chitinases we identified, we took the genes responsible for producing these enzymes from bacteria in the cod's gut and inserted them into another cold-loving bacterium called Aliivibrio wodanis. This bacterium is great for producing proteins at low temperatures. As a result, we successfully produced five different chitinases, and two of them were able to break down chitin in laboratory tests. However, more work is needed to improve the process and produce larger amounts of these working chitinases.
In conclusion, our research highlights the unexploited potential of the Northeast Arctic cod’s intestines, which are often discarded as waste during food production. Microbial communities and enzymes hold immense value for science, industry, and environmental sustainability. From natural food processing to waste reduction and sustainable aquaculture, the microbes in these fish intestines may soon provide benefits far beyond the ocean.
1st Opponent: Dr. Sean P. Kennedy, Institute Pasteur, France
2nd Opponent: Profesor Simen Rød Sandve, Norwegian University of Life Sciences
Internal member and leader of the committee: Dr. Edda Marie Rainer, UiT, IK, UiT
The defence and trial lecture will be streamed from these following links at Panopto:
Defence (31.10.2025 10:00 - 13:00)
Trial Lecture (30.10.2025 14:00 - 14:45)
The thesis is available Here