Identification and characterisation of biosynthetic gene clusters from subsection V cyanobacteria

Abstract

Cyanobacteria are well known producers of natural products, many of which display bioactivities with potential pharmaceutical interest. Cyanobacteria are classified into five subsections based on their morphology, of which the Subsection V are considered to be the most morphologically advanced. Recent genome sequencing projects have led to an increase in the number of publically available Subsection V cyanobacterial genomes, however, the secondary metabolite potential of the majority of these organisms remains elusive. The overall aim of this thesis was to increase the knowledge of the secondary metabolite potential of the Subsection V cyanobacteria, through identification and characterisation of natural product biosynthetic gene clusters from whole genome sequences. This thesis builds upon the recent identification and characterisation of the ambiguine (amb) and welwitindolinone (wel) biosynthetic gene clusters, as well as the identification of NRPS/PKS, PRPS and terpene biosynthetic gene clusters from publically available Subsection V cyanobacterial genomes. The aim of this thesis was to demonstrate the diversity and potential of the Subsection V cyanobacteria to produce secondary metabolites from a range of natural product classes. Furthermore, the aim of this thesis was to characterise the early stages of hapalindole biosynthesis through heterologous expression, and characterise the expression of the mycosporine-like amino acid (MAA) gene cluster under UV-A and UV-B radiation. Genome mining for all classes of natural products was performed within the 11 publically available Subsection V cyanobacteria, in addition to two cyanobacterial genomes sequenced in this study, W. intricata UH strain HT-29-1 and H. welwitschii Uh strain IC-52-3. A biosynthetic gene cluster for hapalosin was identified within three Subsection V cyanobacterial genomes, however, hapalosin has previously only been identified within the cyanobacterium H. welwitschii UH strain IC-52-3. In total, 17 complete orphan NRPS/PKS gene clusters were identified from the Subsection V cyanobacteria. Biosynthetic gene clusters for a number of PRPS (including cyanobactin, microviridin and bacteriocin gene clusters), MAAs, scytonemin, hydrocarbons, terpenes and the hapalindole family of natural products were also identified. Genome mining has revealed the diversity, abundance and complex nature of secondary metabolite potential of the Subsection V cyanobacteria.

Date of Award	2015
Original language	English