Isolation, cultivation and identification of bacteria with potential probiotic use in the cultivation of aquatic organisms: case study with bacteria from the gastrointestinal tract of the sole Paralichthys orbignyanus (Valenciennes, 1839)
By definition, probiotic organisms are those that improve the health of the host, either assisting in the digestion of food and assimilation of nutrients, stimulating the immune system, or acting in the control of pathogenic microorganisms. However, the use of commercial probiotics poses risks to the health of farmed animals and the environment that need to be considered. Bacteria used in commercial products can have antibiotic resistance genes, which can be transferred to pathogenic microorganisms present in the culture environment. Thus, isolation of strains from the host itself would be an alternative to solve this problem. The objective of this work was to isolate, cultivate and identify bacteria, with potential probiotic use in aquatic animals.In this study, the bacteria were obtained from the sole gastrointestinal tractParalichthys orbignyanus(Valenciennes, 1839) grown at the Marine Aquaculture Station of the Federal University of Rio Grande - FURG. Dilutions of material extracted from the gastrointestinal tract were sown in four culture media (TCBS, MRS, MA and NA), incubated and the colonies were isolated and purified. UFC values were low (104 UFC ml -1), probably due to the long period between the collection of intestinal tracts and seeding of bacteria, or due to the transport of this material on ice. Despite this, 94 bacteria were isolated, whose colonies presented in eight different morphotypes. The genomic DNA of 46 isolates from the TCBS and MRSA media was extracted, amplified and purified, and the coding region of the 16S rRNA gene of these microorganisms was sequenced. The bacteria were grouped and identified by the construction of phenograms. The results showed the presence of the genera Brachybacterium , Brevibacterium , Photobacterium and Staphylococcus. Nineteen isolates have not grouped with any existing type lineage, allowing us to suppose that they are species that are not described. As future perspectives, it is proposed to carry out in vitro and in vivo tests to verify the possible action of isolated bacteria as inhibitors of pathogenic bacteria, or in improving the zootechnical performance of P. orbignyanus . In addition, it is intended to obtain probiotic microorganisms isolated from other cultured aquatic organisms.