Bacteria that navigate using magnetic fields could be used to deliver drugs into tumours. The bacteria, Magnetococcus
marinus, have a navigation system based on magnetised crystals to help them find their way around the deep sea. Scientists at the National Institute of Biomedical Imaging and Bioengineering in the US have exploited this ability by injecting the bacteria into mice with cancer. They then generated magnetic fields to guide the bacteria towards the tumours. The next step is to modify the bacteria so they can deploy a cargo of tumourkilling molecules.