Honey bees (Apis mellifera) are globally important pollinators, providing pollination services worth over $15 billion/year in the US alone. However honey bee populations are currently impacted by a wide range issues, including a large number of pathogens and parasites. Nosema species (N. ceranae and N. apis) are common microsporidian parasites of honey bees. Nosema infect honey bee midgut endothelial cells, where they produce spores that subsequently infect additional midgut cells or are shed in the faeces. This lifecycle in the midgut ensures that the parasite interacts with the honey bee gut microbiome. The honey bee microbiome has been well characterised due to its relatively simple structure, with 8-10 dominant bacterial taxa. This study aimed to identify microbiome-parasite interactions that may be involved in the establishment or resistance of Nosema infection following low dose exposure. Known-aged honey bees from three different hives were experimentally exposed to a low dose of Nosema spores in laboratory cage experiments following the natural establishment of their gut microbiome in hives. Two days post exposure, Nosema levels were quantified through qPCR, and a subset of individuals were further analysed to investigate gut microbiome structure.
Results/Conclusions
Bees varied in their response to low dose (100 spore) experimental exposures. Some bees following experimental exposure had no sign of infection (0 – 10 ge), while some bees clearly developed an infection (70-900 ge). This range of infection levels allowed investigations into the variation in gut microbiome communities between these groups. Preliminary metagenomic analysis of a subset of individuals has shown that, control bees (uninfected) harboured more microbial diversity than bees with relatively high Nosema loads. Among isolates that were common across treatments, we find that infected bees exhibited increases in the abundance of particular microbes, relative to controls, after count normalization. These differences could indicate a role for the gut microbiome in controlling bees ability to resist Nosema infection following exposure.