Life in the dark: The microbiomes of mussels from deep-sea hydrothermal vents

The manner in which the microbiome is acquired and persists over the lifetime of hosts shapes the ecology and evolution of both beneficial and pathogenic associations. However, our understanding of microbial acquisition and persistence is still rudimentary, particularly in the vast diversity of life that is not genetically tractable, so-called non-model organisms. Bathymodiolus mussels have fascinated biologists since their discovery in the early 1980s at deep-sea hydrothermal vents. These mussels thrive in the deep sea, far away from the photosynthetic primary production at the ocean surface, thanks to their intimate symbiosis with bacteria that provide them with nutrition. In addition to their beneficial symbionts, bathymodioline mussels also host a pathogen, Ca. Endonucleobacter, that infects their nuclei. A single pathogen invades the mussel's nuclei, replicates there, generating up to 80,000 cells and causing the nuclei to swell to 50 times their original size, and eventually escapes when the infected mussel cell bursts. In my talk, I will describe the combined molecular and imaging approaches we are using to gain insights into how the beneficial and pathogenic microbiota of deep-sea mussels enter and persist in their hosts, and how these processes affect the ecology and evolution of these associations.