False-colour scanning electron micrograph of the soil bacteria Agrobacterium tumifaciens (red) growing on the surface of a cell from the tobacco plant Nicotiana plumbaginifolia. It is known as a natural genetic engineer for the ease with which it interfers with the metabolism of its host. It injects a cancer causing gene into the host which in turn develops a tumour that is food for the bacterium. Its ability to act as a vector has brought it to the attention of geneticists. Using this bacterium, cells can be infected with foreign genes conferring resistance to disease or stimulating chemicals such as insulin and interferon. Magnification: x1500 at 6x4. 5cm