Siderophores

Siderophores, iron-scavenging small molecules (iron chelators), are fundamental to bacterial nutrient metal acquisition facilitating cellular iron transport.
Raymond et al. 2003 Proc. Natl. Acad. Sci. USA 100: 3584-3588
Perry et al. 2019 Proc Natl Acad Sci USA 116: 21980–21982

Siderophores are synthesized and secreted by certain Commensal Bacteria / Commensalism and pathogens, and act to retrieve iron, an essential nutrient, from the environment
Kim et al. 2017 Immunol Rev. 279(1): 90-105

see also:
Colorectal Cancer (CRC) & Iron