## 3 Results and Discussion
### Analysis of Plasmid Presence and Antibiotic Resistance Genes  
The genome of _Lentzea_ sp. JNUCC 0626 contains a second circular contig measuring 177,940 bp with a GC content of 70.12%, harboring 197 predicted proteins (Figure 2b). This study aims to investigate the potential presence of plasmids or bacteriophages in _L. jejuni_. In microbial genome analysis, differentiating between plasmids and bacteriophages is achieved by identifying specific genes unique to each entity. Although both plasmids and phages are classified as mobile genetic elements, they can be distinguished by their distinct protein expression profiles. The genomic analysis of _Lentzea_ sp. JNUCC 0626 revealed essential genes for plasmid functionality within the second circular DNA contig. These genes encode homologous proteins critical for plasmid transfer, including a Type IV secretory system conjugative DNA transfer protein from _Alloactinosynmema_ sp. L-07 (XJI)19586.1; identity 81%), a Type IV secretion system protein from _Amycolatopsis sai/feldensis_ (XJI)19590.1; identity 60%), and a ParA family protein from _Pseudonocardiaceae bacterium_ YIM PH 21723 (XJI)19448.1; identity 54%) (GenBank: CP171636.1). Type IV secretion system (T4 SS) proteins play a critical role in plasmid functionality by initiating plasmid DNA transfer through conjugation, enabling horizontal gene transfer between adjacent cells [40]. They also form the essential components of the machinery that translocate plasmid DNA across the cell membrane from donor to recipient cells [41]. ParA proteins ensure stable plasmid maintenance by facilitating the proper partitioning of plasmid DNA during cell division. Without ParA or its partner proteins, plasmids may be lost or unequally distributed to daughter cells, leading to instability [42]. Importantly, the second circular contig of _Lentzea_ sp. JNUCC 0626 contains a gene homologous to L,D-transpeptidase, which may function as an antibiotic resistance gene. L,D-transpeptidase is an enzyme involved in bacterial cell wall synthesis and is particularly linked to resistance against \(\beta\)-lactam antibiotics. Unlike conventional D,D-transpeptidases, L,D-transpeptidases can form crosslinks between peptides containing both L- and D-amino acids. While \(\beta\)-lactam antibiotics inhibit D,D-transpeptidases, L,D-transpeptidases remain unaffected, enabling bacteria to sustain their antibiotic resistance. In conclusion, the presence of these genes strongly supports the existence of plasmids within _Lentzea_ sp. JNUCC 0626, suggesting that these plasmids may play a significant role in gene transfer and contribute to the genetic diversity of microbial populations. Furthermore, the identification of plasmids could pave the way for developing host-vector systems in _Lentzea_ sp. JNUCC 0626, facilitating the application of combinatorial biosynthesis in actinobacterial hosts for the production of novel bioactive compounds. In Silico Prediction of Secondary Metabolites and Biosynthetic Gene Cluster Analysis of Lentzea sp. JNUCC 0626  
Genome mining and the antiSMASH program are powerful tools for discovering novel secondary metabolites derived from microorganisms. Genome mining involves exploring microbial genomes to identify potential compounds, while antiSMASH supports this exploration through efficient and automated means. Together, these approaches significantly advance the discovery and understanding of new secondary metabolites [43; 44; 45]. In this study, we performed a comprehensive genome analysis and an antiSMASH analysis of _Lentzea_ sp. JNUCC 0626. As shown in Table 1, we identified 34 BGCs including those related to terpenes, indolocarbazoles, nucleosides, peptides, polyketides, and peptidyl-polyketide hybrids. Subsequently, we conducted a homologous protein analysis of these individual BGCs using the National Center for Biotechnology Information (NCBI) databases. The protein structural characteristics were further analyzed using prediction programs such as AlphaFold, SWISS-MODEL, and HHPred.