## 3 Results and Discussion
### Analysis of Plasmid Presence and Antibiotic Resistance Genes
#### 3.6.4 Indole-Related Gene Clusters  
The antiSMASH analysis predicted the presence of an indolocarbazole BGC in _Lentzea_ sp. JNUCC 0626 BGC region 7, which shares 85% of the biosynthetic genes found in BE-54017, a natural product derived from uncultured bacterium AB1650 that belongs to the indolotryptoline family and exhibits potent activity against tumor cell lines [53]. As shown in Figure 6, Table 2 and Table S20, proteins XJIJ15613 through 1138 in BGC region 7 display high amino acid identity with the corresponding proteins from the BE-54017 BGC, including AbeC (89.87%), AbeO (90.27%), AbeY (86.74%), AbeF (89.38%), AbeT (84.93%), AbeH (95.15%), AbeM3 (89.32%), AbeX2 (92.03%), AbeD (93.10%), AbeM1 (90.91%), AbeX1 (93.43%), and AbeM2 (91.30%). However, we observed the absence of two key proteins, AbeR and AbeP, in _Lentzea_ sp. JNUCC 0626 BGC region 7. Further analysis revealed that protein XJIJ15613 is located at the terminus of BGC region 7, prompting us to search the full genome contig for downstream proteins. Upon comparison with the BE-54017 BGC, we identified protein XJIJ15611, which shares 71.37% amino acid identity with the LuxR-like transcription regulator AbeR, and protein XJIJ15612, which shares 86.60% amino acid identity with the RebP-like cytochrome P450 AbeP. This study provides two key insights: first, that antiSMASH results may miss certain BGC components when homology is low or when the BGC is located at the genomic region's boundary, underscoring the importance of in silico walking; and second, that a complete BE-54017 BGC is indeed present in the _Lentzea_ sp. JNUCC 0626 BGC region. BGC Region 20 Derived from _Lentzea_ sp. JNUCC 0626  
The antiSMASH analysis predicted that region 20 is associated with an indole-related BGC based on the homology of protein XJIJ18501 to tryptophan dimethylyltransferase. The structural comparison of protein XJIJ18501 with crystal structures from the PDB, conducted using SWISS-MODEL and HHPred, confirmed its high similarity to _Micromospora olivastrospona_ 6-dimethylallyl tryptophan synthase (PDB: 6 ZRY) and _Marinactinosoma metrololearans_ indole prenyltransferase MpnD (PDB: 4 YLA). Furthermore, the structure of protein XJJ18502 was analyzed in comparison to PDB crystal structures using HHPred, revealing significant similarity to _Proteus vulgaris_ tryptophan indole-lyase (PDB: 9 BNJ), _Butyricococcus_ sp. BIOML-A1 tryptophananese (PDB: 8 SL7), and _Fusobacterium variant_ tryptophanase (PDB: 8 SIJ). Recently, the Mara1 enzyme, which contains indole preyltransferase and tryptophan indole-lyase domains, has been identified as a key player in maramycin biosynthesis. Thus, it is proposed that the putative indole prenyltransferase MarA and tryptophan indole-lyase MarB in BGC region 20 may be instrumental in the production of maramycin intermediates [54]. Downstream of MarA and MarB, five proteins (XJJ18494 to XJ18498) exhibit homology to glycosyltransferases, while protein XJ18499 shows homology to an FAD-dependent oxidoreductase, and protein XJ18500 is similar to lysyl oxidase. In contrast, the upstream proteins (XJJ18503 to XJ18506) resemble ATP/GTP-binding proteins, DUF742 domain-containing proteins, roadblock/LC7 domain-containing proteins, and nitrate- and nitrite-sensing domain-containing proteins (see Figure S12 and Table S21). Ultimately, these proteins do not appear to be involved in the biosynthesis of maramycin and mansouramycin. An intriguing aspect is the presence of the IS30 family transposase gene XJJ19173, located adjacent to the tryptophanase upstream region. According to the BLASTP analysis, three proteins--XJJ19304, XJJ19318, and XJJ19371--were identified within the genome of _Lentzea_ sp. JNUCC 0626, all sharing 100% amino acid identity with XJ19173 and consisting of 375 amino acids. The phenomenon of multiple instances of IS30 family transposases within microbial genomes may arise from various transposition and genomic evolution