## 3 Results and Discussion
### Analysis of Plasmid Presence and Antibiotic Resistance Genes
#### 3.6.5 NRPS and PKS Gene Clusters  
BGC Region 8 Derived from _Lentzea_ sp. JNUCC 0626  
We conducted an antiSMASH analysis of the complete genome of _Lentzea_ sp. JNUCC 0626 and identified two secondary metabolite BGCs for NRP and enediyne sporolide A/B within a large BGC, region 8, which is composed of approximately 100 genes. Based on these findings, we aimed to estimate the BGC boundary by investigating the transcriptional orientation, operon potential, and functions of the biosynthetic enzymes involved. The first BGC is related to siderophore biosynthesis. Protein XJJ15775, which shows homology to the SidA/IucD/PvdA family of monooxygenases, likely plays a critical role in siderophore biosynthesis. These enzymes are primarily involved in the N-hydroxylation of L-ornithine or L-lysine, essential reactions for the formation of hydroxamate siderophores. For example, SidA, found in _A. fumigatus_, hydroxylateds L-ornithine to synthesize hydroxamate-based siderophores such as ferriccin and fusarinine. IucD is involved in the biosynthesis of hydroxamate siderophores such as aerobactin, primarily hydroxylating L-lysine. PvdA is essential for the biosynthesis of pyoverdine, a siderophore in _P. aeruginosa_, and catalyzes the hydroxylation of amino acids. These enzymes are critical in siderophore biosynthesis because they mediate the formation of hydroxamate groups, which are essential for strong iron-binding properties [59]. On the other hand, protein XJ15774, which shows similarity to FAD-dependent tricarballylate dehydrogenase, is an enzyme involved in oxidizing tricarballylate to aconitate in the TCA cycle and does not appear to be directly associated with siderophore biosynthesis [60]. Additionally, protein XJ15790, which shows homology to 2,3-dihydroxybenzoyl al adenylate synthase, may play a significant role in siderophore biosynthesis. It utilizes 2,3-dihydroxybenzoate (2,3-DHB) and ATP as substrates to form an adenylate intermediate (2,3-DHB-AMP), a key step observed in the biosynthesis of catechol siderophores [61]. In contrast, protein XJ15792 shows similarity to pyridoxal kinase, an enzyme that phosphorylates pyridoxal into pyridoxal-5\({}^{\prime}\)-phosphate (PLP), a form of vitamin B6 [62]. However, it has no known direct role in siderophore biosynthesis. In conclusion, the NRP of BGC region 8 likely corresponds to a siderophore compound, with the BGC boundary consisting of seventeen enzymes, including two NRPSs, six transporters, two siderophore-interacting proteins, an MbtH family NRPS accessory protein, a phosphopantethe-binding protein, decarboxylase, methyltransferase, a lysine N(6)-hydroxy/L-ornithine N(5)-oxygenase protein, and (2,3-dihydroxybenzoylyl) adenylate synthase. These enzymes are predicted to span from protein XJ1J5775 to XJ1J5790, including XJ15779 (Figure S13, Table S22). The second BGC is associated with enediyne biosynthesis. Protein XJ1J5814.1 shows homology to NAD-dependent epimerase/dehydratase and shares 46.68% identity and 55.53% similarity with Sporolide SpoT8 [63]. Additionally, proteins XIJ15813 (maleylpyruvate isomerase), XIJ19084.1 (acetyl-CoA carboxylase), and XIJ15814.1 are translationally coupled, suggesting their inclusion within the Ene gene cluster of _Lentzea_ sp. JNUCC 0626. Meanwhile, protein XIJ15811 shows the highest similarity to carotenoid oxygenase, an enzyme involved in the oxidative reactions of carotenoids, which is crucial for generating various bioactive compounds through the degradation and modification of carotenoids [64]. However, no evidence suggests that carotenoid oxygenase directly participates in enediyne biosynthesis. Protein XIJ15812, located between proteins XIJ15811 and XIJ15813, shows similarity to the TetR/AcrR transcriptional regulator, with the transcriptional direction of the two adjacent proteins being reversed. Interestingly, the stop codon of protein XIJ15813 overlaps with the coding region of protein XIJ15812.