Research

Our lab studies functional and evolutionary aspects of microbial symbiosis focusing on the gut microbiota of honey bees and related social bees. We address general questions of gut microbiology and aim to understand the role of the microbiota for bee health.

Genomics of gut symbionts

Microbial communities residing in animal guts are typically dominated by specialist bacteria, adapted to live in the gut of a given host (Ley et al. 2008). Consequently, these bacteria must encode dedicated symbiotic functions in their genomes involved in host interactions. We use different sequencing technologies and comparative analyses to mine the genomes of honey bee gut symbionts for genes involved in symbiosis. Findings from these analyses display the basis for further experimental investigations of symbiotic roles of bee gut bacteria (see ‘Symbiotic functions of gut bacteria’). Furthermore, we use the genomic information to understand the evolution of gut communities. Like in mammals, bee gut bacteria have diversified by adapting to different host species, but also by colonizing different niches in the gut (Kwong et al. 2014, Engel et al. 2014, Engel et al. 2012). Our genomic approaches allow us to analyze diversification of gut communities and to understand the evolutionary driving forces of their complexity and diversity.

Genome_circle_v1Partial representation of the genome map of a honey bee gut symbiont and comparison to genomes of related bacteria. Such analyses allow us to identify gene sets specific to honey bee gut symbionts hinting towards functions involved in adaptation in the gut.

 

Symbiotic functions of gut bacteria

The gut microbiota of animals typically consists of several, sometimes hundreds of different bacterial taxa living together in the gut of the same host. Little is known about the genetic basis of gut bacteria to interact among each other and with the host. We aim to reveal novel genetic determinants and mechanisms with key roles for symbiosis in the gut. The honey bee is an ideal model to discover and study such determinants because the gut microbiota has a relatively simple composition compared to other animals and harbors bacteria specifically adapted to this environment. This allows us to study a well-defined symbiotic system with a limited number of interactions and assess their underlying genetic determinants.

Bee_GutFluorescence in situ hybridization (FISH) experiment visualizing two gut bacteria colonizing the epithelial cell surface of the honey bee gut. The gammaproteobacterial gut symbiont G. apicola is shown in magenta, the betaproteobacterial gut symbiont S. alvi is shown in green. Counterstain with DAPI in blue shows DNA of bacteria and host nuclei.

 

Impact of gut bacteria on honey bee health

As pollinators, the honey bee represents a key species in nearly all terrestrial ecosystems, and plays a central role for the human food supply. Its global economical value has been estimated to account for €150 billions annually (Gallai et al. 2009; Bauer & Wing 2010). Therefore, recent reports on bee population declines have alerted scientists and bee keeping industries around the world, and a better understanding of factors influencing the health status of this important pollinator is of broad interest and urgent need (Genersch et al. 2010; Evans & Schwarz 2011). The gut microbiota is likely a vital contributor to the health of the honey bee and previous findings provide strong evidence for the presence of intimate and highly specific interactions with the host (Engel et al. 2012; Kwong et al. 2014). Our lab wants to understand how the microbiota impacts bee health and which bacteria contribute in which way. Our primary focus lies on microbiota-mediated effects on nutrition and interactions with pathogens.