Social communication between microbes colonizing the social honey bee Apis mellifera
The European honey bee (Apis mellifera) is a charismatic species that plays a critical role in the pollination of agriculturally important crops and native flora. One emerging field of research is that of the host-associated honey bee microbiome: a group of bacterial phylotypes consistently found within the honey bee, which may play critical roles such as protection from pathogens and nutrient acquisition. In other model systems, host-associated microbial communities are known to participate in a form of bacterial communication known as quorum sensing. This type of communication allows bacteria to sense their environment and respond with changes in gene expression, controlling a number of factors including virulence, biofilm formation, and cell motility. Here, we have investigated the production of a specific quorum sensing molecule by honey bee microbes in vivo and in vitro. We specifically focused on the inter-species signaling molecule, autoinducer-2 (AI-2). We identified the production of AI-2 by both the entire community (using honey bee gut homogenates) and by cultured isolates, using a Vibrio harveyi biosensor. By comparing newly emerged and adult bees, we showed this signal is likely coming from the core microbial community. Finally, using honey bee specific bacterial isolates, we identified changes in biofilm production when isolates are exposed to increased levels of exogenous AI-2. Altogether, these data provide multiple lines of evidence for the presence of quorum sensing inside the honey bee host. The effect of AI-2 on biofilm formation by honey bee specific bacteria identifies one potential avenue for quorum sensing to affect host health.\n\nAuthor summaryMicrobial communities associate with every animal on the planet and can have dramatic effects on the health of their host. The honey bee is one such animal, home to a characteristic community of bacteria, which may provide various benefits. Here, we show that these microbes are producing quorum sensing molecules which could support interactions between bacterial members and facilitate host colonization.