## 3 Results
### Prediction of Antibiotic Gene Cluster Similarities  
The potential of the _Streptomyces_ isolates to produce antibiotics and other secondary metabolites was predicted using antiSMASH (version 4), which compared our unknown gene sequences with previously documented antibiotic/secondary metabolite biosynthetic gene clusters (BGC). These BGCs contain the genes necessary to produce secondary metabolites, including enzymes and pathway-specific regulatory genes.  
We identified many BCGs in the genomes of the six strains of _Streptomyces_ from the Blessed clay using antiSMASH. Many of the gene cluster similarities identified are common in _Streptomyces_, including albaflavenone (a sesquiterpene antibiotic) [25], alkylresorcinol [26], desferrioxamine (a siderophore that mitigates cytotoxicity to doxorubicin) [27], ectoine [28], isorenieratene (a bacterial chlorophyll) [29], and melanin [30]. These compounds are recorded here because of their potential synergy with antibiotics [31]. Most importantly, there were also similarities between the gene sequences we identified in these _Streptomyces_ and several antibiotic gene synthesis clusters, including those for polycyclic tetramate macrolactams (SGR PTM), candicidin, griseochelin, cypemycin, and cyslabdan [31; 32; 33; 34; 35].  
AntiSMASH identified several gene clusters in whole genome sequences of _Streptomyces_ isolates McG1 and McG5 with similarities to the lantibiotic cypemycin (77%) (Figure 2a).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Isolate** & **Size (Mb)** & \begin{tabular}{c} **Config** \\ **Numbers** \\ \end{tabular} & \begin{tabular}{c} **Contig N50** \\ **(Kb)** \\ \end{tabular} & \
\begin{tabular}{c} **Longest** \\ **Contig (Kb)** \\ \end{tabular} &
\begin{tabular}{c} **Biosynthetic** \\ **Gene Clusters** \\ \end{tabular} \\ \hline McG2 & 6.912 & 1189 & 9.0 & 70.7 & 25 \\ McG3 & 8.720 & 586 & 23.6 & 125.6 & 39 \\ McG5 & 7.026 & 1079 & 11.8 & 70.7 & 27 \\ McG6 & 6.874 & 1524 & 7.3 & 62.2 & 24 \\ McG7 & 7.143 & 465 & 26.0 & 82.9 & 12 \\ McG8 & 7.304 & 653 & 18.3 & 62.7 & 12 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Summary statistics of the genomes of _Streptomyces_ isolates. Number of biosynthetic gene clusters is based on antiSMASH analysis.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Gene Cluster** & **Shared** & **BGC Data Link** & \multicolumn{6}{c}{_Streptomyces_** **Isolates McG**} \\ \hline  & & & **1 \({}^{*}\)** & **2** & **3** & **5** & **6** & **7** & **8** \\ \hline Cypemycin & 77\% & BGC0000582\_cl & \(\blacktriangledown\) & & \(\blacktriangledown\) & & & \\ Candicidin A & 66\% & BGC0000034\_cl & & \(\blacktriangledown\) & & \(\blacktriangledown\) & & \\ Griseochelin & 84\% & BGC0001821\_cl & \(\blacktriangledown\) & & \(\blacktriangledown\) & & & \\ SGR\_PTMs & 83\% & BGC0001043\_cl & & \(\blacktriangledown\) & & & & \\ Cyslabdan & 81\% & BGC0001910\_cl & & & & & \(\blacktriangledown\) & \(\blacktriangledown\) \\ \hline \hline \end{tabular}
\end{table}
Table 5: Biosynthetic gene cluster (BGC) similarities between _Streptomyces_ isolates and known antimicrobial synthesis genes. The biosynthetic gene clusters are hyperlinked to their corresponding matches in the Minimum Information about a Biosynthetic Gene cluster (MIBiG) repository. Abbreviation: _Streptomyces griseus_ polycyclic tetramate macrolactam (SGR PTM). \({}^{*}\)_Streptomyces_ sp. McG1 [14].  
Genes from _Streptomyces_ sp. McG3 showed similarities to the griseochelin (zincophorin) biosynthesis cluster (Figure 2b). Boho _Streptomyces_ sp. isolates McG1 and McG3 had similar gene sequences to biosynthesis clusters for SGR PTM, a polytetramic macrolactam [36] (Figure 2c). _Streptomyces_ strains McG2, 5, and 6 had gene similarities to biosynthesis clusters for candicidin, an antifungal antibiotic [37] (Figure 2d). Finally, the WGS of _Streptomyces_ isolates McG7 and McG8 showed similarities to gene clusters for cyslabdan [32].