Proteomics of Ca. Riegeria standrea – the chemosynthetic symbionts of the marine flatworm Paracatenula from the Bay of Sant´Andrea (Elba, Italy)

Paracatenula are marine catenulid flatworms occuring in shallow water sediments. Adult Paracatenula lack a mouth and a digestive system. Instead, a trophosome containing intracellular alphaproteobacterial symbionts, namely Ca. Riegeria fill most of the worm´s body (Gruber-Vodicka et al., 2011). Paracatenula sp. ‘standrea’ that harbor Ca. Riegeria sp. 812A (standrea) were sampled in Elba, Italy in April 2016. Based on the genome of Ca. Riegeria sp. 812A (standrea) we discovered a versatile combination of storage and biosynthesis and a convergence with unrelated intracellular thiotrophic symbionts. Proteomic analyses were performed to investigate which symbiont genes related to the host nutrition were expressed.