Ph.d trial lecture and public defence: Lokesh Jeppinamogeru - FBA

03 November 2016 10:15 - 03 November 2016 15:30

Auditorium Elsa Laula Renberg (A12), Nord universitet, Bodø

Lokesh Jeppinamogeru will hold a trial lecture and defend his thesis on microbiota of Atlantic salmon for the degree Philosophiae Doctor (PhD) at the Faculty of Biosciences and Aquaculture.

Title of thesis:

Microbiota of Atlantic salmon (Salmo salar L.), during their early and adult life

Title of trial lecture:

"Comparative aspects of the microbiota in fish immunity"

Time for trial lecture:
10:15 - 11:15
Time for defence: 12:15 - 15:30

Main supervisor: Professor Kiron Viswanath, FBA
Co-supervisor: Professor Jorge Fernandes, FBA
Co-supervisor: Professor Truls Moum, FBA

Members of the Evaluation Committee:
- Professor Axel Kornerup Hansen, Section Experimental Animal Models, Institute for Veterinary Diseases, University of Copenhagen
- Research Scientist Trond M. Kortner, Department of Basic Sciences and Aquatic Medicine, Norwegian University of Life Sciences
- Associate Professor Margarita Novoa Garrido, FBA, Nord University

PhD trial lecture and defence are open for the public. The thesis is available, contact Kristine Vevik,, tel +47 75 51 74 37.  

About the thesis:

Atlantic salmon is a high-value fish that is farmed for food. The production of the fish has been steadily increasing over the years; correspondingly there is a constant need for developing sustainable management strategies, including those for improving health. Manipulation of the host microbial communities is a potential strategy to achieve the goal, but this requires an in-depth knowledge on the community. In the present thesis a 16S ribosomal RNA (16S rRNA) gene sequencing technique was employed to study the early-life, intestinal and skin microbiota of Atlantic salmon.

Early-life bacterial communities (of eggs and hatchlings) of Atlantic salmon had 17 different phyla, though the most abundant OTUs belonged to the phylum Proteobacteria. The egg-associated microbiota was relatively less diverse compared to the hatchlings. Interestingly, there was a shift in the bacterial community composition of the eggs during the incubation period. Hatching coincided with a rapid rise in the community richness. The phylogenetic content of the early intestinal communities was affected by feeding. The intestinal communities of the fish in freshwater were dominated by Firmicutes, whereas the fish in seawater had Proteobacteria as the dominant phylum. The core presumptive metabolic pathways did not differ much between the groups, but some pathways were characteristic of certain stages.

The transfer from freshwater to seawater was found to have a significant effect on the skin communities, even at one week after transfer. The genus Oleispira (Proteobacteria) was more abundant in the seawater group, four weeks after the transfer. In addition, the skin communities also revealed the presence of some opportunistic bacteria. The metabolic potential of the community in the freshwater fish was abundant with pathways involved in the degradation of common water pollutants, whereas the bacteria of the seawater fish were associated with the pathways responsible for extracting energy required for their metabolism, and biosynthesizing compounds needed for structural changes that facilitates their survival in the changing environment.

The composition of the intestinal communities of the adult fish from different sources revealed that the abundant bacteria were distinct in the different populations, even at the phylum-level. Proteobacteria was abundant in the wild fish from freshwater, whereas the fish in sea cages and controlled environment were abundant with Tenericutes. 

Collectively, this thesis catalogues the microbes present in the early life stages, skin and intestine of Atlantic salmon. In addition, the variations in the abundant phylotypes are also mapped.  The information will be helpful for manipulating the communities in order to improve the health of farmed Atlantic salmon.