Caption

Nanobacterium, bacterium and virus. Coloured elec- tron micrograph of a bacterium (left), nanobacter- ium (right) and virus (far right). This composite image shows their relative sizes. Nanobacteria (nanobes) are thought to be the smallest self- replicating organisms. They were found in 200 million year old sandstones from 3-5 kilometres below the seabed. When the rocks were opened, the nanobes multiplied and grew in the laboratory. They contain DNA (deoxyribonucleic acid), which contains the instructions for life. They were discovered by Philippa Uwins at the University of Queensland, Australia. Magnification unknown.