Gut symbionts and the role they play in fungal pathogen suppression of honey bee brood

Social insects have multiple levels of defense that include: individual innate immune responses; a collective colony-level immune response known as social immunity; and finally, the full set of recently discovered gut symbionts that can generate an additional level of immune response. So far there has been limited research showing how these gut microbial communities contribute to honey bee immunity and overall health; making this an important yet underexploited topic in understanding honey bee biology. We studied the ecological and genetic basis of interactions between honey bee larvae, their associated gut microbes, and pathogens. Using an in vitro rearing approach, honey bee larvae were removed from colonies several hours post hatching and kept in incubators under constant temperature and humidity. The larvae were exposed to recently identified gut microbiota in combination with obligate and facultative brood fungal pathogens that are known to cause chalkbrood and stonebrood disease. We were able to demonstrate that honey bee larval survival was positively affected by the presence of gut mictobiota and we suggest possible targeted immune genes that might be involved in these symbionts interactions.