 The study examined two types of symbiotic relationships between anelidworms and their bacteria. The first type was a heterotrophic relationship between the bone-eating worm Ostax francpressi and its endosymbiont bacterium, while the second type was a chemo-autotrophic relationship between the deep-sea vestimentifrim worm and its endosymbiont bacterium. The study found that both symbiotic relationships had unique characteristics, but they also shared similarities. For example, both symbiotic relationships involved the loss of certain genes and the gain of others. Additionally, both symbiotic relationships relied on the ability of the endosymbiont bacterium to provide essential nutrients for the host worm. This article was authored by Giacomo Moggioli, Baelic Panoshin, Jainin Sun, and others.