Relationships among biosystems are identified during the NCBI data processing procedures, and then presented as "Related BioSystems" in the (a) "Find Related Data" menu in the right margin of search results pages; (b) in the "Related information" menu in the right margin of individual biosystem record displays; and (c) in the folder tabs shown in an individual biosystem record. Options (b) and (c) are illustrated below.
Types of related biosystems include:
- Linked BioSystems - the source database has explicitly stated the biosystems are connected in some way
- Similar BioSystems - share at least one identical protein sequence from the same source organism. In other words, the biosystems include a protein that is in the same protein identity group (PIG) and has the same Taxonomy ID (TaxID). An example is shown in the illustration below.
- Biosystems that have an evolutionary relationship, such as an Organism Specific BioSystem that is an instance of a canonical, Conserved BioSystem. (For example, human arachidonic acid metabolism (bsid82991) is an organism-specific instance of the conserved biosystem for arachidonic acid metabolism (bsid366). The conserved biosystem record, in turn, links back to the human and other organism-specific instances of the biosystem, reflecting the relationships specified by the source database, KEGG.)
- Biosystems that have a functional relationship with each other, either as a Superset of smaller biological processes or a Subset of, or small reaction within, a larger biological process. (For example, "Phase 1 - Functionalization of compounds" (bsid105699) is a superset biosystem that includes "COX reactions" (bsid105711) as one of its subset biosystems, reflecting the hierarchical organization of those biosystems specified by the source database, Reactome.)