Abstract:[Background] The probiotic and pathogenic properties of Enterococcus faecalis are strain-specific, and probing into the physiological characteristics and genomic features is of great significance for evaluating the application value of E. faecalis.[Objective] To investigate the physiological characteristics and genomic features of a strain of E. faecalis isolated from the intestine of Large-Tailed Han sheep. [Methods] The strain was isolated by anaerobic culture in the modified GAM medium and identified by 16S rRNA gene sequencing. Its physiological characteristics were analyzed through growth and acid production curves. The genomic sequence of this strain was obtained by Illumina and PacBio high-throughput sequencing, which was followed by sequence assembly and analysis by bioinformatics tools. Additionally, the antibiotic resistance of this strain was examined. [Results] A non-spore- forming, gram-positive coccus was successfully isolated and identified as E. faecalis based on 16S rRNA gene sequencing results. The strain entered the logarithmic phase at the time point of 2 h, reached its growth peak at the time point of 6 h, and exhibited acid production from the early stage of the experiment. The genome of the strain consisted of one circular chromosome and two circular plasmids, with a total length of 2 992 873 bp, G+C content of 37.26%, and 2 810 genes. Functional analysis indicated that the genes were primarily involved in key biological processes, such as carbohydrate transport and metabolism, translation, ribosome structure and biogenesis, and transcription. The genome contained five genomic islands, three prophages, and six CRISPR/Cas systems, which played significant roles in the adaptive evolution of the strain. Additionally, gene clusters related to the synthesis of secondary metabolites were identified, closely associated with the production of antimicrobial substances. The strain carried 413 genes, which can reduce its virulence by interfering with the expression of resistance and pathogenic genes, thereby inhibiting its pathogenicity. Antimicrobial susceptibility test results showed that the strain was highly sensitive to ampicillin, piperacillin, and penicillin, moderately sensitive to streptomycin and erythromycin, and resistant to cefalexin and cefuroxime sodium. [Conclusion] We successfully isolated a sheep-derived strain E. faecalis LTHS1, whose genome was rich in metabolism-related genes. This strain can aid in the digestion and absorption of nutrients in the animal gut and exert antimicrobial effects through secondary metabolites. These findings provide a theoretical basis for the research and application of this strain in microbiology, medicine, and animal husbandry.
