Abstract: Described herein are methods for detecting a microorganism or cell in a subject and methods for detecting, imaging or diagnosing a site, disease, disorder or condition in a subject using microorganisms or cells. Also described are methods which use microorganisms or cells for treating a disease, disorder or condition. Such sites, diseases and disorders include sites of cell proliferation, proliferative conditions, neoplasms, tumors, neoplastic disease, wounds and inflammation. Further described are microorganisms and cells for use in the methods and compositions, combinations and kits, including diagnostic and pharmaceutical compositions, containing a microorganism or cell. Microorganisms and cells described herein include those that bind, sequester or accumulate metal, such as those that provide for metal acquisition, transport, storage and/or metabolism. Additional imaging and therapy agents are also described.