Gut symbiotic associations of microorganisms with their respective hosts are omnipresent in nature and have substantially affected animal evolution. Some microbes are harmful or even lethal to their hosts and are referred to as parasites or pathogens, while others that play pivotal biological roles for their hosts are known as mutualists. Stink bugs that feed on plant sap or seeds commonly harbor mutualistic bacteria in gut crypts, wherein symbionts play pivotal metabolic roles, including nutritional recycle. Noteworthy about the stink bug gut symbiosis is its simplicity: only a single bacterial species is associated in the gut. My research focus is to clarify the underpinning mechanisms of this super-specific gut symbiosis.
The bean bug Riptortus pedestris, a notorious pest of leguminous crops, acquires a Burkholderia symbiont from ambient soil and harbors it in midgut crypts. Considering the enormous diversity of soil microbiota, it is astonishing that the bean bug winnows bacteria in the gut and achieves the simplest gut microbiota. In this presentation, I’ll summarize recent findings in the molecular bases of the bug-Burkholderia gut symbiosis, particularly focusing on how partner-choice and competition-based mechanisms play a role to maintain simplicity.