Vasciaveo, Sara;
(2025)
Genome mining for novel sactipeptides.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
The continuing rise of antimicrobial resistance poses a challenge for medicine. The emerging class of natural products ribosomally synthesised and post-translationally modified peptides (RiPPs) are a diverse group of biologically active antibacterial molecules and therefore an encouraging addition to antibiotics. Increasing numbers of RiPP natural products have been identified in recent decades thanks to the advances in genome sequencing. The biosynthetic gene clusters (BGCs) of known RiPP classes such as lanthipeptides, ranthipeptides, and sactipeptides, are identified by the presence of conserved genes, and the product’s structure can be predicted depending on the type of enzymes encoded in the cluster. Previous research on genome mining has shown that the use of bioinformatics tools such as BLAST and RODEO can be used in mapping of RiPP classes such as sactipeptides via the radical S-adenosylmethionine (rSAM) enzymes, uncovering hundreds of new BGCs. In this study, the promiscuity of the rSAM enzyme AlbA was investigated to explore its potential to create a sactipeptide library. Enzymatic studies proved challenging and thus genome mining was employed to identify putative sactipeptides and their BGCs. This led to the discovery of a novel sactipeptide named SVP1 in the bacteriocin-producing bacterium Bacillus smithii DSM 4216. SVP1 was extracted and purified, and its structure was characterised through high-resolution mass spectrometry, tandem mass spectrometry, and circular dichroism spectroscopy. Its antimicrobial activity was also tested against a panel of Gram-positive bacteria. Furthermore, the svpA gene was heterologously expressed in subtilosin producer Bacillus subtilis 168, successfully leading to the production of the peptide SVP1. This exciting result indicates the promiscuity of the post-translational modifying enzymes in the subtilosin biosynthetic pathway, including the thioether forming radical SAM enzyme, AlbA. The promiscuity of these enzymes is contrary to that reported in recent literature and opens new avenues raising important questions regarding sactipeptide biosynthetic pathways.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Genome mining for novel sactipeptides |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2025. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > Div of Biosciences |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10203744 |
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