A synthetic biology approach to the biosynthesis of novel pyrrole-amide antibiotics

• Main Author: Cortés Sánchez, Antonio Emilio
• Published: University of Strathclyde 2016
• Subjects: 615.3
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.720314

Novel antibiotics are desperately needed. We are on the verge of the pre-antibiotic era, with bacteria resistant to last resort drugs spreading quickly worldwide. Natural products, or chemical molecules produced by living organisms, evolved over time to interact with biological targets following rules that researchers have not yet outlined fully. However microorganisms, once the source of most of the drugs we use today, were abandoned in favor of synthetic chemistry, under the false premise that natural sources were depleted. When pursuing novel antimicrobials, two options are in hand, either drug discovery or drug functionalisation. In this thesis, approaches that were left on the golden era of antibiotic discovery due to technological limitations are revisited to produce derivatives of congocidine and distamycin. These two natural products are pyrrole-amide peptide antibiotics, characterised by antibiotic, antifungal, antiviral and antitumoral properties, which arise from their non-covalent DNA-binding properties. Since both antibiotics are chemically very close, this thesis explores the combinatorial biosynthetic opportunities to exploit between the pathways that encodes them. Their chemical outline enables them to bind rich AT sequences in the minor groove of the DNA, with different preferred motifs according to specific differences in peptide length and functional groups. Research on synthetic compounds imitating these two natural products, have shown that the DNA binding affinity can be modulated by peptide length and heterocycle content. As synthetic chemistry represents an inefficient approach for the production of these derivatised compounds based on the natural scaffold of concocidine, the in-vivo substitution of the pyrrole rings for other heterocycles such as imidazole or thiazole is pursued through a mutasynthetic approach. The last part of this study focuses on the resistance mechanism present in both clusters. Since both antibiotics are closely related, the study of their resistance mechanism can help understand how natural antimicrobial evolution shapes natural antibiotic resistance, and the structure to activity relationship of novel compounds are explored.