Coral reefs are the most diverse of all marine ecosystems, harboring about 25 % of all ocean biodiversity. The coral population has been an approximately 30% worldwide decline, over the past 30 years, largely due to emerging diseases such as coral bleaching, which is the most serious disease threatening coral reefs. Coral bleaching may be caused by a number of stress factors, including bacterial infections. Despite the impact of bleaching, the mechanism that initiates the infection and the agents involved is not completely elucidated. Only a few infective agents have been identifying, including Vibrio species, which are widely distributed in the marine environment. However, the pathogenesis of these bacteria was only observed with temperatures above 26°C. Among the main pathogenic species described in the literature, is highlight: V. alginolyticus, V. coralliilyticus, and V. shiloi. Although of the several studies described in the literature, the relationships between bacteria infections and the bleaching coral remain unclear. Therefore, the present work investigated if the effect of culture temperature (22 and 28 0C) would have significant influence on the secondary metabolism of V. alginolyticus in order to correlate them with the pathogenesis in corals. V. alginolyticus (A-407) was cultured in two 2 L erlenmeyer flasks each containing 1 L of the culture medium (10 g/L of soluble starch, 2 g/L of yeast, 4 g/L of peptone, dissolved in 750 mL of artificial seawater and 250 mL of distilled water) at 22 and 28 °C with shaking. After seven days, the broth was extracted with EtOAc and evaporated under reduced pressure to yield the organic extract. Both extracts were analyzed in HPLC/DAD for obtaining the chemical profile. The extract at 28 °C (156,8 mg) was subjected to open-column chromatography on C18-reversed phase silica gel, eluted with a step gradient of methanol and water. Four fractions were obtained (FR1 to FR4) and the FR3 fraction (31,2 mg) contained a mixture of metabolites, which was further fractionated by reversed-phase HPLC (Phenomenex Luna C18(2), 250 × 100 mm, 3 mL/min, 5 μm, UV = 210 nm) using an isocratic solvent system of 10% CH3OH in H2O to afford a dipeptide cyclo-L-prolyl-L-tyrosine (3,0 mg - retention time 28.77 min). Up to now, the literature has not yet reported the isolation of this dipeptide from bacteria of the genus Vibrio.
Keywords: Coral reef, Vibrio, dipeptide.
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