Marine nematode symbioses

Stilbonematids (Desmodoridae, Chromadoria) are marine nematodes coated with sulfur-oxidizing bacteria. They are the only known marine metazoans capable of establishing monospecific ectosymbioses. Hundreds of highly specialized hypodermal glandular sensory organs (GSOs) appear to play a fundamental role in symbiosis establishment and maintenance: they produce the mucus the symbionts are embedded in.
In the course of our ongoing research project, we want to study abundantly expressed stilbonematid genes discovered by pyrosequencing-based transcriptome analysis. Among these, some are secreted by the GSOs onto the worm's surface and might play a role in symbiosis. In order to understand their function, we will analyze their expression pattern within the GSO and try to silence them by RNA interference.
Concomitantly, we will start to explore how the microbial partners manage to divide without loosing physical contact with their hosts. This requires a highly unusual division mode in which the fission plan is set longitudinally to the symbiont long axis.

The study of relatively simple, naturally occurring symbioses may be instrumental in understanding how beneficial and pathogenic microbes interact with the mucosal surfaces of higher vertebrates.