Meeting Abstract
Although many insects engage in herbivory and likely rely on gut-associated bacteria to provision their diets, very few have been studied in detail. The ants provide an excellent system to study the diversity, distribution, and influence of gut-associated bacteria as herbivory has evolved many times (we can ask how diet influences associations), we have a well-resolved phylogeny for the group (to understand the role of shared evolutionary history or convergence), and ants are distributed around the world (permitting us to control for shared environment). Using next-generation sequencing we have found a diversity of bacteria associated with ants, with several key bacterial groups represented in herbivorous species, including Rhizobiales and Burkholderiales. Using the turtle ants, genus Cephalotes, we have several lines of indirect and direct evidence on the role these bacteria play in up-regulating their hosts diet. Specifically we find that some core gut bacteria are upregulated when turtle ants are feed diets that contain pollen, a food source very few organisms have been able to successfully leverage due to the heavily defended pollen cell wall. We also find the densest bacterial communities in the part of the ant digestive tract where the Malpighian tubules, which are responsible for excreting urea, come into contact with the digestive tract. Leveraging labeled nitrogen and antibiotic manipulations of the host to knock down/out their resident gut bacterial communities we demonstrate that the gut bacteria of the turtle ant provides essential amino acids to the host. In addition, using metagenome sequencing of the gut-associated bacteria we find the core bacteria from Cephalotes can synthesize essential amino acids.
