Metabolic perturbations and bacterial communities dysbiosis associated with skin ulcer disease progression in Sepia pharaonis

Skin ulcer disease causes massive mortalities during the culture of the cuttlefish Sepia pharaonis. In the present study, metabolomic and 16S rRNA sequence were used to investigate the variation in metabolites and bacterial communities in the skin tissue of S. pharaonis with skin ulcer symptom. S. pharaonis were collected at the undiseased stage (UDS), early diseased stage (EDS), and agonal stage (AS) during a severe and highly contagious skin ulcer disease on the fin. Significantly lysis of the epidermal cells in the skin tissue at both the AS and EDS groups were observed under microscope. Specific metabolic changes responding to disease were identified using metabolomic analysis. Choline continually increased while osmotic chemicals including betaine, homotaurine, and trehalose, decreased; variable levels of phosphocholine and AMP related to energy, and decreased GSH/ GSSG ratio related to intense oxidative stress disturbed the balance of osmoregulators, energy and redox equilibrium. 16S rRNA sequence showed a significant decrease in Pseudomonas spp. and Acinetobacter spp., but an increase in Vibrio spp. as the disease progressed. Gammaproteobacteria and Bacillus spp. can be used as biomarkers for the skin ulcer disease, while Pseudomonas spp. and Acinetobacter spp. were the potential probiotics for S. pharaonis culturing. Our present results indicated the characteristic changes in metabolic profile and bacterial community as the disease progressed, which would offer basic information for the further understanding of the disease occurrence in S. pharaonis culturing.