The fish gut microbiota plays an important role in overall health. However, few reports have described the changes in the composition of gut microbiota following infection with pathogenic bacteria in olive flounder (Paralichthys olivaceus). Here, we reported the changes in the gut microbiota composition of flounder after treatment with each of the three pathogenic bacteria (Edwardsiella tarda, Streptococcus iniae, and Vibrio harveyi). Edwardsiella tarda infection decreased the relative abundance of Verrucomicrobia and increased Proteobacteria abundance at the phylum level of the gut microbiota over time. Similarly, Streptococcus iniae infection reduced the relative abundance of Verrucomicrobia. Vibrio harveyi infection caused a decrease in the relative abundance of Firmicutes and Verrucomicrobia and increased Proteobacteria. At the genus level, infection with all three pathogens increased the relative abundance of Ralstonia and Sphingomonas species. Conversely, this infection decreased the relative abundances of Rubritalea, Saccharimonas, and Bacillus species. Therefore, reducing the abundance of Ralstonia and Sphingomonas and increasing the abundance of Rubritalea, Saccharimonas, and Bacillus in the gut microbiota composition of flounder might help maintain a healthy gut microbiota balance. This research might be useful for future studies on improving the health of flounder through gut microbiota regulation.

So Young Park, Jin Won Choi, Dong Nyoung Oh, Eun Ji Lee, Dong Pil Kim, Sun Jay Yoon, Won Je Jang, Sang Jun Han, Seungjun Lee, and Jong Min Lee. J. Microbiol. Biotechnol. 2023;33:621-33. https://doi.org/10.4014/jmb.2212.12005

Yun Young Kang, Hyo Jeong Song, So Young Park, Dong Nyoung Oh, Ga Yeong Kim, Na Yeong Been, Da Yeong Kim, Eun Ji Lee, Bo-Hye Nam, and Jong-Min Lee. J. Microbiol. Biotechnol. 2025;35:1-13. https://doi.org/10.4014/jmb.2411.11045

This study investigated the properties of Latilactobacillus curvatus MS2 isolated from Korean traditional fermented seafood as probiotics and the effect of reducing cholesterol as a synbiotic with isomalto-oligosaccharide (IMO) in BALB/c mice. The isolated strain showed high resistance to acids and bile acids and exhibited a high DPPH scavenging capacity of 72.27 ± 0.38 %. In the intestinal adhesion test using HT-29 cells, the adhesion rate of MS2 was 17.10 ± 1.78 %, which was higher than the adhesion rate of the other investigated probiotics. MS2 showed good antimicrobial activity against food-borne pathogens, especially Staphylococcus aureus, S. epidermidis, Escherichia coli, and Vibrio vulnificus. This strain had high availability for IMO among the prebiotics of fructo-oligosaccharide, inulin and IMO. Oral administration of MS2 and IMO to BALB/c mice for 5 weeks resulted in a significant reduction in blood cholesterol levels by regulating liver lipid metabolism. These results suggest that the combination of MS2 and IMO has potential for application in functional foods.