UC Davis

Host-microbe interactions underlie the development and fitness of many macroorganisms; microbial symbionts can facilitate digestion, mitigate pathogens, and even produce essential developmental cues. My dissertation focuses on the impacts of microbes within the plant-pollinator system, investigating the crucial and complex interactions between bees, plants, and microbes- with a focus on how microbes use specialized tools to influence pollen processes, bee development, and the wider microbial community. Through use of classical natural history observations combined with entirely novel experimental and sampling approaches, I have been able to discover unique phenomena in microbial ecology that not only have important implications for pollinator systems but have changed broader perception and understanding of ecology and evolution. Chapter 1 explores the role of nectar-associated bacteria, particularly Acinetobacter pollinis, in facilitating pollen digestion. By inducing pollen germination and bursting, these bacteria access critical nutrients, with implications for pollinator nutrition and the role of flower associated microbes in pollinator systems. Chapter 2 examines the developmental microbiome of a solitary bee, revealing that immature stages of Anthophora bomboides standfordiana host a distinct core microbiome dominated by Actinobacteria and a yeast-like fungus, Moniliella spathulata. Data from microbial community profiling, qPCR, and functional experiments support the hypothesis that the bee’s microbial community may provide critical fitness advantages, such as pathogen protection (Streptomyces) and enhanced cold tolerance (M. spathulata) during the bees’ diapausing larval stage- suggesting that microbes play a vital role in the bees’ overwintering success and long-term survival. Chapter 3 builds on these findings by describing two novel species, Streptomyces solapis sp. nov. and Streptomyces nidicoloris sp. nov., isolated from the brood of A. bomboides. These new bee- associated species display unique biosynthetic gene clusters that correlate with antifungal activity, underscoring the potential of leveraging the diversity of microbial symbionts to support discovery of new bioactive compounds. Collectively, this dissertation highlights the profound influence of microbes on macroorganisms, offering broader insights into the dynamics of pollination ecology, host-microbe symbioses, and the unique evolutionary strategies of microbes in these environments.