Hobson, Christian (2019) Biosynthesis and bioengineering of antibiotics in Burkholderia species. PhD thesis, University of Warwick.

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Abstract

The emergence of antibiotic resistance combined with the decline in the discovery of novel antibiotic scaffolds has led to an urgent need for the development of effective antimicrobial treatments. Recently a Gram-negative genus of bacteria, Burkholderia, has been shown to be an untapped source of antimicrobial compounds. Two such compounds produced by Burkholderia are gladiolin and enacyloxin IIa (figure 1), which are active against the multidrug resistant pathogens Mycobacterium tuberculosis and Acinetobacter baumannii respectively. Both compounds are assembled by polyketide synthases, but there are parts of the biosynthesis of both natural products that are not well understood.

Figure 1 The structures of gladiolin and enacyloxin IIa.

The installation of the E,Z-diene motif in gladiolin (red, figure 1) was investigated using an intact protein MS-based assay with chemically synthesized polyketide intermediate mimics. The diene was shown to be installed by an unprecedented double dehydration, which appears to be conserved for the installation of dienes in some other polyketide natural products based on bioinformatics analyses. The biosynthesis of the dihydroxycyclohexanecarboxylic acid (DHCCA) unit of enacyloxin IIa (blue, figure 1) was also investigated using in vitro biochemical assays. The initial hypothesis for the pathway was shown to be incorrect, and the elucidation of the correct pathway also led to the discovery of a new potential biocatalyst.

Using multiple biosynthetic engineering strategies that rely upon a thorough understanding of enacyloxin IIa biosynthesis, a library of enacyloxin IIa analogues was generated. This provided useful structure-activity relationship (SAR) data with regards to the binding of enacyloxin IIa to its target, EF-Tu. Five enacyloxin IIa analogues were also generated which had improved biological activity. These analogues may provide a platform for the rational engineering of improved enacyloxin IIa analogues harboring more complex structural changes.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	Q Science > QD Chemistry
Library of Congress Subject Headings (LCSH):	Burkholderiales, Biosynthesis, Antibiotics -- Synthesis, Drug resistance in microorganisms
Official Date:	June 2019
Dates:	Date Event June 2019 UNSPECIFIED
Institution:	University of Warwick
Theses Department:	Department of Chemistry
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Challis, Gregory L.
Format of File:	pdf
Extent:	xiv, 284 leaves : illustrations
Language:	eng

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