The Isolation, Identification, and Whole-Genome Sequencing of a Potential Probiotic, Clostridium butyricum YF1, Isolated from the Intestine of the Ricefield Eel (Monopterus albus)

<i>Clostridium butyricum</i>, recognized as a probiotic, is widely distributed in the intestines of various animals. In this study, the <i>C. butyricum</i> strain YF1 was isolated from the intestine of the ricefield eel (<i>Monopterus albus</i>) using an anaerobic culture method and was identified through morphological, physiological, biochemical, and 16S rRNA sequence analyses. Notably, <i>C. butyricum</i> YF1 exhibited a rapid growth rate and was found to produce ten types of short-chain fatty acids, particularly high-yield acetic acid and butyric acid. Additionally, YF1 demonstrated a high tolerance to elevated temperatures (70 °C), bile salts (0.1% to 0.5%), artificial intestinal fluid, and artificial gastric fluid, while being sensitive to most antibiotics. Further whole-genome sequencing revealed that <i>C. butyricum</i> YF1 has a total genome size of 4,314,266 bp and contains 3853 coding genes. Specifically, 82 tRNAs, 21 rRNAs, 288 repeat sequences, 13 prophages, and two gene islands were detected. Moreover, gene function analysis indicated that the highest number of genes were annotated to metabolic processes, and the butyric acid metabolism pathway was found to be complete. Meanwhile, 598 virulence genes and 186 resistance genes were predicted. In conclusion, the findings from this study contribute to probiotic development and provide innovative approaches for the sustainable and healthy cultivation of ricefield eels.