Sulfur, carbon and nitrogen metabolism in chemosynthetic nematode symbioses

Current projects

My PhD explores a fascinating animal-bacterium symbiosis, the one engaging interstitial marine nematodes belonging to the Stilbonematinae. They are unique in the sense that every worm species carries on its surface a single Candidatus Thiosymbion phylotype, thereby establishing a one-to-one (binary) ectosymbiosis. Despite being globally distributed in shallow water marine sediments and at abundances so high as to potentially influence sediment geochemical cycles, we still do not know which molecules do the partners exchange and whether it is because of this metabolic exchange that the partners associate. Based on seminal ecological studies, it has long been hypothesized that the symbionts associate with the nematodes to exploit their vertical migrations through the redox zone, that is to alternatively access O(e- acceptor) in the upper sand layers and sulfide (e- donor) in the deeper ones. During my PhD I have been testing this hypothesis by subjecting Laxus oneistus to deep sand- and superficial sand-like conditions and comparing its transcripts, proteins, lipids and storage compounds. To this aim, I applied a broad array of techniques including comparative Transcriptomics, Lipidomics (in cooperation with M. Mauss and Y. Chen, Warwick), Proteomics (in cooperation with S. Markert, Greifswald) and Metabolomics (in cooperation with Dubilier, Bremen), qPCR, stable isotope-based techniques (e.g. 13C and 15N2 incorporation tracking via Mass Spectrometry and NanoSIMS in cooperation with R. Lee, A. Schintlmeister and M. Wagner), Raman Spectroscopy (in cooperation with  M. Palatinszky and D. Berry) and in situ measurements (oxygen, sulfide, DIN, etc.). Besides helping to understand how Stilbonematinae could contribute to S, C, and N cycling in marine sediments, my studies may provide the physiological basis of the extraordinary reproductive strategy this symbiont evolved (Weber et al., 2019).

Approach/Methods: Stable isotopes, Mass spectrometry, NanoSIMS, TEM, Transcriptomics, Metabolomics

Student: Gabriela Fabiola Paredes

Faculty: Bulgheresi

Funding: FWF