The present invention relates generally to the field of endosymbiosis, eukaryotic cells engineered with artificial endosymbionts, and magnetotactic bacteria. In particular, the invention provides single-celled organisms such as artificial endosymbionts, including magnetotactic bacteria, eukaryotic cells to host those single-celled organisms, and methods of using eukaryotic cells containing single-celled organisms. The invention also provides eukaryotic cells engineered with intracellular single-celled organisms which eukaryotic cells can be tracked in an animal and monitored for viability. The invention also provides for multimodal detection of a eukaryotic cell in an animal to monitor the location and viability of the eukaryotic cell.
