Microbial diversity in the intestine of olive flounder (Paralichthys olivaceus)

The gastrointestinal tract is colonized by micro-organisms which have either beneficial or harmful effects on the host. In spite of the economic importance of olive flounder, Paralichthys olivaceus, there is, only limited information on microbial diversity in the intestine. In order to examine microbial diversity and richness in the gut of olive flounder, we collected intestinal mucus from both farmed and wild fish in order to examine the micro-organisms present. All the isolates were equated into four phyla, Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes. Overall, there was significant difference between wild and farmed fish in terms of microbial richness. In particular, 13 species of lactic acid bacteria (LAB): Pediococcus lolii, Streptococcus salivarius, Lactococcus lactis, Enterococcus durans, Leuconostoc lactis, Weissella cibaria, Lactobacillus sakei, Pediococcus pentosaceus, Lactococcus chungangensis, Weissella thailandensis, Lactobacillus brevis, Lactobacillus crustorum, and Lactobacillus oligofermentans, were isolated from the intestine. Species richness and abundance of LAB in the intestine of wild fish are significantly greater than that of farmed fish (which had been fed with industrially formulated feeds), suggesting that formulated diets are not as favorable some components for LAB as those diets encountered in nature. This indicates that wild fish may be an important source of potentially beneficial micro-organisms including LAB.