Department of Genetics In Ecology

Marine nematode symbioses

Duration: 10.06.2010 - 09.06.2013

FUNDING

PARTICIPANTS

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.

Legend: Fluorescence In Situ Hybridization confocal microscope pictures of symbiotic Robbea sp.1 (A-C), sp.2 (G-I) and sp.3 (M-O). Bacterial symbionts on each worm are double stained with a eubacterial-specific probe (green) and a symbiont-specific probe (red); the respective overlay is shown in C, I and O. Dashed lines in M-O indicate the Robbea sp.3´s surface.
Robbea sp.1 and sp.3 symbionts are stained with a Gammaproteobacteria-specific probe (D and P, blue), but not with a nonsense control probe (E and Q, red), as clearly shown in the overlay pictures F and R, respectively. Robbea sp.2 symbionts are stained with the eubacterial-specific probe (green), but not with a nonsense control probe (red), as evident in the overlay (L). Scale bar is 4 µm.

Recent publications

Heindl NR, Gruber-Vodicka HR, Bayer C, Luecker S, Ott JA, Bulgheresi S. 2011 First detection of thiotrophic symbiont phylotypes in the pelagic marine environment. FEMS Microbiol Ecol. Mar 23. doi: 10.1111/j.1574-6941.2011.01096.x. [Epub ahead of print]

Bulgheresi S, Gruber-Vodicka HR, Heindl NR, Dirks U, Kostadinova M, Breiteneder H, Ott JA. 2011 Sequence variability of the pattern recognition receptor Mermaid mediates specificity of marine nematode symbioses. ISME J. Jan 13. [Epub ahead of print]

Bright M, Bulgheresi S. 2010 A complex journey: transmission of microbial symbionts. Nat Rev Microbiol. 2010 Mar;8(3):218-30. Review.