Scientists have written a message into the DNA of a living organism, a breakthrough they believe could lead to a new era of organic computers capable of healing themselves if damaged. The researchers encoded Einstein's most famous equation and most prolific year into the genome of one the hardiest strains of bacteria in the world, Bacillus subtilis. The characters "E=MC^2 1905!" were then read from the bacterium at a later date by analysing its genetic sequence.

In the proof-of-principle experiment, the research team showed they could write a message into the bacterium's DNA and retrieve it. The process is slow, taking days to complete. But because the organisms are so hardy and are able to pass on data to future generations, they may still find a role in storing large amounts of information that do not need to be accessed quickly.

Yoshiaki Ohashi, who led the study at Keio University in Tokyo, said that bacteria have the potential to store vast quantities of data and are more resistant to the kinds of damage that could wipe modern hard drives. "Information storage using DNA is robust for more than one hundred million years," he said.

The researchers wrote the message by first converting it into binary. This code was then built into artificial strands of DNA, using letters such as AG to mean 1000 and TC to mean 0111. The strands were then injected into the bacterium.

A difficulty is that bacteria are promiscuous when it comes to swapping DNA with other microbes. But the team believe the mutation rates are slow enough to ensure messages are still readable, especially when the bacteria form a tough spore.

Professor Ohashi said the process would work equally well in plants, fruit and insects. "Cockroaches are very interesting, because they have an ability to tolerate [extreme] environments."

While the researchers' main goal is to create living memories for a new breed of DNA computers that perform calculations using strands of genetic material, the technique could also be used to tag organisms for life, by inserting identification markers into their genome. The research is published in the journal of the American Chemical Society.

In 2004 Israeli scientists used DNA to power the world's smallest computer, a molecular computer designed to identify traces of prostate and lung cancer in blood and deliver a DNA-based treatment telling the cancerous cells to self-destruct.