Skin responses in Atlantic salmon post-smolts during exposure to Tenacibaculum finnmarkense

Tenacibaculum finnmarkense is a novel Gram-negative, aerobic bacterial strain causing skin ulcers in Atlantic salmon. This is an emerging pathogen, which may cause serious problems to aquaculture. The study was designed to compare the life stages (smolt and posmolt) and to assess effects of environment (fresh and brackis water) on the course of disease and salmon responses to the pathogen. The experiment was conducted at ILAB Bergen, Norway. The facility includes two units. Fish kept in the holding unit in fresh or brackish water is referred to as holding controls. Smolts and postsmolts were moved to the challenge unit and full-strength seawater (34 ppt) was applied 24 hours prior to the challenge with Tenacibaculum finnmarkense strain HFJT. Groups from the challenge unit are referred to as control and infected. To follow the development of the challenged skin, samples were taken three days post challenge. Ventral skin samples for microarray analysis were selected based on ulcer scoring. For each sample, RNA from epidermis and dermis was isolated separately. Total RNA was extracted using the automated Biomek 4000 (Beckman Coulter).