Microbial Communities Associated with Ambrosia Beetles and the European Honey Bee, Apis mellifera.

摘要

Symbiosis has shaped most, if not all, living organisms. For example, beneficial microbes influence the nutrition, development, reproduction and defense of their hosts. In this dissertation I examine the microbial communities associated with ambrosia beetles and honey bees. I begin by briefly introducing key concepts and terms in the field of symbiosis, and proceed by reviewing the basic biology of both ambrosia beetles and honey bees, and what is known about their associated microbial communities. In the second chapter, I investigate ambrosia beetles for Actinobacteria-based defensive mutualisms. I consistently isolated one actinobacterial lineage from the two ambrosia beetle species examined, a representative of which could inhibit the growth of a putatively antagonistic fungus, but not the mutualistic fungus via production of the natural product cycloheximide. In chapter three, I further investigate Actinobacteria based defensive mutualisms of honey bees. I isolated a high diversity of Streptomyces Actinobacteria from bees and their hive components, several of which inhibited the growth of common insect pathogens. One common isolate was shown to produce a novel antibiotic compound, named apinimycin, that specifically inhibits growth of the most common and devastating honey bee bacterial pathogen, American foulbrood (Paenibacillus larvae ). The identification of actinobacterial-derived natural products that inhibit the growth of parasites supports the hypothesis of bacterial defensive mutualisms in ambrosia beetles and honey bees. In the fourth chapter, lipid composition is used to describe the broad microbial communities associated with honey bees and their hives. I show that the communities associated with honey bees appear to be structured more by hive component (e.g., worker bees, pupae, honey, comb, propolis and pollen stores), than hive, geographic location, or collecting year. My thesis work suggests that insect symbioses with antibiotic-producing bacteria are more widespread than currently recognized, and underscores the complexity of microbial-insect associations.