Proteomic profiling of salmon skin mucus for the comparison of sampling methods.

The epidermal mucus protects fish against harmful environmental factors and the loss of physiological metabolites and water. It is an efficient barrier between the fish and the biosphere. The integrity of the skin mucus is thus of vital importance for the welfare and survival of the fish. Since excreted proteins and small molecules in the mucus can mirror the health status of the fish, it is a valuable matrix for monitoring stress, pathogen exposure, and nutritional effects. Several methods for sampling epidermal mucus from different fish species have previously been described, but information about their efficiency or the comparability of mucus analyses is lacking. In the present study, skin mucus from farmed Atlantic salmon was therefore sampled by three methods, including absorption or wiping with tissue paper, and scraping with a blunt blade, and the mucus proteome was analyzed by ultra-high pressure liquid chromatography high-resolution mass spectrometry. The measured protein contents, numbers, compositions and the observed data quality were compared between sampling methods. Furthermore, functional annotation and classification of the identified proteins was performed. The results showed that the three skin mucus sample types differed qualitatively as well as quantitatively. The absorbed mucus was the least tainted by proteins resulting from damage inflicted to the fish epidermis by the sampling procedure. Wiped mucus showed a better protein yield than absorbed and delivered a larger proteome of identifiable proteins, with less contamination from epithelial proteins than observed for scraped mucus. We recommend that future research of mucus should use the absorption method in cases, where it is important that the mucus is devoid of proteins from the underlying epithelium, and the wiping method, when protein yield is crucial or when the proteome of the outer epithelium is of interest.

Effects on mortality and stress response in European sea bass, Dicentrarchus labrax (L.), fed mannan oligosaccharides (MOS) after Vibrio anguillarum exposure.

The effects of dietary mannan oligosaccharides (MOS; 4 g kg(-1) ; Bio-Mos, Alltech Inc, USA) in diets for European sea bass, Dicentrarchus labrax (L.), juveniles in relation to disease and stress resistance, combining intestinal infection with Vibrio anguillarum and stress challenge by confinement, were assessed in this study. After 8 weeks of MOS supplementation, fish were exposed to a pathogen challenge test against V. anguillarum by direct gut inoculation combined with a confinement stressor panel. Cumulative mortality of fish fed MOS caused by anally inoculated V. anguillarum decreased from 66% to 12.5% and from 54.1% to 25% in infected and infected + stressed fish, respectively, compared to fish fed control diet. Results for European sea bass revealed a positive effect of MOS dietary inclusion on disease resistance, in terms of cumulative mortality, against gut inoculated V. anguillarum, as well as reduced effects of stress on microbiota diversity. Both of these findings, together with the enhanced innate immune response and the higher gut mucus production and density of eosinophil granulocytes in gut mucosa obtained in previous studies after MOS supplementation (Torrecillas et al. 2007, 2011a,b) suggest that general reinforcement of the innate immune system, and particularly of the intestinal barrier efficiency, is the main defence mechanism of European sea bass fed MOS against pathogenic microorganisms.

Novel application of nitrifying bacterial consortia to ease ammonia toxicity in ornamental fish transport units: trials with zebrafish.

AIMS: To evaluate whether two commercial nitrifying bacterial consortia can function as biocontrol agents in ornamental fish transporting systems. METHODS AND RESULTS: The consortia were applied in a simulated set-up using zebrafish as the model organism in three trials. The efficacy of the bacterial consortia in controlling the ammonia level was validated by measuring water quality parameters such as total ammonia, nitrate and pH of the transport water. The bacterial community structure in the transport unit was studied using denaturing gradient gel electrophoresis. The consortia tested improved the nitrifying activity that in turn facilitated the reduction of ammonia that had accumulated during the transport. Bacterial profiles revealed the presence of both ammonia-oxidizing and nitrite-oxidizing bacteria in the transport bags. CONCLUSIONS: The application of the consortia during the transportation of zebrafish could profoundly improve the water quality by curbing ammonia accumulation. SIGNIFICANCE AND IMPACT OF THE STUDY: The potential of applying nitrifying bacteria as a bioremediation practice during the transport of ornamental fish has been demonstrated and this innovative approach contributes to the amelioration of current fish welfare in ornamental fish trade.