The role of microorganisms in shaping the nectar chemistry of mānuka plants (Leptospermum scoparium) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Ecology at Massey University, Manawatū, New Zealand. EMBARGOED until 9 September 2024.

Embargoed until 9 September 2024Mānuka (Leptospermum scoparium) honey is one of the main export products from New Zealand. The distinctiveness of this honey comes from the floral nectar, which possesses dihydroxyacetone, a carbohydrate with UV protection capabilities, which converts to methylglyoxal, usually during the honey maturation process. Methylglyoxal gives mānuka honey its biological activity (antimicrobial and antioxidant properties) and is often used as a quality marker. While it is acknowledged that microorganisms play an important role in plant ecology, their abundance and impact on nectar chemistry remain understudied. Microorganisms can arrive in the nectar by pollinator activity or through the phloem and can change nectar chemical properties. This thesis aims to fill a gap in the knowledge of the microbial diversity of the nectar; the impact of pollinators in the microbial nectar community, and the effect of bacteria on dihydroxyacetone production and sugar content in mānuka nectar. To achieve this aim, a combination of metagenomics, bacterial cultivation, chemical analyses, and biological in vivo and in vitro assays was conducted.--Shortened abstrac