Parasaccharibacter apium, gen. nov., sp. nov., Improves Honey Bee (Hymenoptera: Apidae) Resistance to Nosema.

The honey bee, Apis mellifera L., is host to a variety of microorganisms. The bacterial community that occupies the adult worker gut contains a core group of approximately seven taxa, while the hive environment contains its own distribution of bacteria that is in many ways distinct from the gut. Parasaccharibacter apium, gen. nov., sp. nov., is a hive bacterium found in food stores and in larvae, worker jelly, worker hypopharyngeal glands, and queens. Parasaccharibacter apium increases larval survival under laboratory conditions. To determine if this benefit is extended to colonies in the field, we tested if P. apium 1) survives and reproduces in supplemental pollen patty, 2) is distributed throughout the hive when added to pollen patty, 3) benefits colony health, and 4) increases the ability of bees to resist Nosema. Parasaccharibacter apium survived in supplemental diet and was readily consumed by bees. It was distributed throughout the hive under field conditions, moving from the pollen patty to hive larvae. While P. apium did not significantly increase colony brood production, food stores, or foraging rates, it did increase resistance to Nosema infection. Our data suggest that P. apium may positively impact honey bee health.

Alternative measures of response to Pseudomonas aeruginosa infection in Drosophila melanogaster.

Studies of invertebrate immune defence often measure genetic variation either for the fitness cost of infection or for the ability of the host to clear the parasite. These studies assume that variation in measures of resistance is related to variation in fitness costs of infection. To test this assumption, we infected strains of the fruit fly, Drosophila melanogaster, with a pathogenic bacterium. We then measured the correlation between host bacterial load and the ability to survive infection. Despite the presence of genotypic variation for both traits, bacterial load and survival post-infection were not correlated. Our results support previous arguments that individual measures of immune function and the host's ability to survive infection may be decoupled. In light of these results, we suggest that the difference between tolerance and resistance to infection, a distinction commonly found in the plant literature, may also be of value in studies of invertebrate immunity.