Trophosome

A trophosome is a highly vascularised organ found in some animals that houses symbiotic bacteria that provide food for their host.

[4] The trophosome can be differentiated between anterior and a posterior area due to incremental changes in host tissue organization, the amount of bacteriocytes, the size and shape of symbionts.

[4] While a structural variant of the frenulate trophosome seems to occur, this organ typically consists of two epithelium and blood spaces sandwiched between the basal matrix of the epithelia in which the inner one is composed of bacteriocytes and the outer one is the coelomic lining.

[4] The trophosome of vestimentiferans is a complex, multi-lobed body with a vascular blood system that covers the entire trunk region.

The trophosome in Osedax is made up of non symbiotic bacteria that reside between the muscle layer of the body's wall and the peritoneum in the ovisac and root regions; therefore, it is derived from the somatic mesoderm.

[12] In both these animals, the symbiotic bacteria that live in the trophosome oxidize sulfur or sulfide found in the worm's environment and produce organic molecules by carbon dioxide fixation that the hosts can use for nutrition and as an energy source.

Trophosome observed high activity of ribulose-1,5-bisphosphate carboxylase / oxygenase and ribulose 5-phosphate kinase, the enzymes of the Calvin-Benson CO2 fixation cycle.

[16] It is important to notice that the observed activities of two enzymes, ribulose-1,5-bisphosphate carboxylase / oxygenase and ribulose 5-phosphate kinase, are present at high concentrations in the trophosome, but are absent in the muscle.

[17] Furthermore, rhodanese, APSreductase, and ATP-sulfurylase are involved in adenosine triphosphate synthesis using the energy found in sulfur compounds such as hydrogen sulphide.

[citation needed] In Riftia pachyptila, the glycogen content of 100 μmol glycosyl units g−1 fresh wt determined in the trophosome is divided equally between host and symbionts.