The effects of amino acids and fatty acids on the disease resistance of Epinephelus fuscoguttatus in response to Vibrio vulnificus infection.

Mass mortality resulting from bacterial infection poses a major problem in the grouper aquaculture industry. The purpose of this study was to profile the metabolites released in challenged fish and to reconstruct the metabolic pathways of brown marble grouper (Epinephelus fuscoguttatus) in response to Vibrio vulnificus infection. Metabolite profiles from control and challenged treatment groups after feeding were determined using gas chromatography-mass spectrometry (GC-MS). Forty metabolites were identified from the GC-MS analysis. These metabolites comprised of amino acids, fatty acids, organic acids and carbohydrates. The profiles showed the highest percent area (33.1%) for leucine from the amino acid class in infected fish compared to the control treatment group (12.3%). Regarding the fatty acid class, a higher percent area of the metabolite 8,11-eicosadienoic acid (27.04%) was observed in fish infected with V. vulnificus than in the control treatment group (22.5%). Meanwhile, in the carbohydrate class, glucose (47.0%) was the metabolite in the carbohydrate class present at highest percentage in the control treatment group compared to infected fish (30.0%). Our findings highlight the importance of a metabolic analysis for understanding the changes of metabolites in E. fuscoguttatus in response to bacterial infections.

Metabolite profiling of Epinephelus fuscoguttatus infected with vibriosis reveals Omega 9 as potential metabolite biomarker.

In this study, we report the starvation effect and vibriosis infection on a tropical fish, the tiger grouper (Epinephelus fuscoguttatus). The tiger groupers were infected with Vibrio vulnificus for 21 days. Gas chromatography-mass spectrometry combined with multivariate analysis was used to assess the variation in metabolite profiles of E. fuscoguttatus. Metabolite productions in infected fishes were significantly influenced by fatty acid production. The Omega 9 (ω-9) was abundant under the challenged conditions compared to Omega 3 (ω-3) and Omega 6 (ω-6). A total of six fatty acids from the ω-9 group were detected in high concentration in the infected fishes compared to the control groupers. These metabolites are Oleic acid, Palmitoleic acid, 6,9-Octadecenoic acid, 8,11-Eicosadienoic acid, cis-Erucic acid and 5,8,11-Eicosatrienoic acid. The production of ω-9 differed significantly (p ≤ 0.001) in the challenged samples. The detected ω-9 compounds were quantified based on three different extraction techniques with Supelco 37-component FAME mix (Supelco, USA). The highest concentration of ω-9 groups compared to the other fatty acids detected is 1320.79 mg/4 g and the lowest is 939 mg/4 g in challenged-starved; meanwhile, in challenged-fed, the highest concentration detected is 1220.87 mg/4 g and the lowest is 917.25 mg/4 g. These changes demonstrate that ω-9 can be used as a biomarker of infection in fish.

Homogeneous Nature of Malaysian Marine Fish Epinephelus fuscoguttatus (Perciformes; Serranidae): Evidence Based on Molecular Markers, Morphology and Fourier Transform Infrared Analysis.

Taxonomic confusion exists within the genus Epinephelus due to the lack of morphological specializations and the overwhelming number of species reported in several studies. The homogenous nature of the morphology has created confusion in the Malaysian Marine fish species Epinephelus fuscoguttatus and Epinephelus hexagonatus. In this study, the partial DNA sequence of the 16S gene and mitochondrial nucleotide sequences of two gene regions, Cytochrome Oxidase Subunit I and III were used to investigate the phylogenetic relationship between them. In the phylogenetic trees, E. fuscoguttatus was monophyletic with E. hexagonatus species and morphology examination shows that no significant differences were found in the morphometric features between these two taxa. This suggests that E. fuscoguttatus is not distinguishable from E. hexagonatus species, and that E. fuscoguttatus have been identified to be E. hexagonatus species is likely attributed to differences in environment and ability to camouflage themselves under certain conditions. Interestingly, this finding was also supported by Principal Component Analysis on Attenuated Total Reflectance-Fourier-transform Infrared (ATR-FTIR) data analysis. Molecular, morphological and meristic characteristics were combined with ATR-FTIR analysis used in this study offer new perspectives in fish species identification. To our knowledge, this is the first report of an extensive genetic population study of E. fuscoguttatus in Malaysia and this understanding will play an important role in informing genetic stock-specific strategies for the management and conservation of this highly valued fish.

Application of 16s rDNA and cytochrome b ribosomal markers in studies of lineage and fish populations structure of aquatic species.

The most economically important form of aquaculture is fish farming, which is an industry that accounts for an ever increasing share of world fishery production. Molecular markers can be used to enhance the productivity of the aquaculture and fish industries to meet the increasing demand. Molecular markers can be identified via a DNA test regardless of the developmental stage, age or environmental challenges experienced by the organism. The application of 16s and cytochrome b markers has enabled rapid progress in investigations of genetic variability and inbreeding, parentage assignments, species and strain identification and the construction of high resolution genetic linkage maps for aquaculture fisheries. In this review, the advantages of principles and potential power tools of 16s and cytochrome b markers are discussed. Main findings in term of trend, aspects and debates on the reviewed issue made from the model of aquatic species for the benefit of aquaculture genomics and aquaculture genetics research are discussed. The concepts in this review are illustrated with various research examples and results that relate theory to reality and provide a strong review of the current status of these biotechnology topics.