One of the essential components of a computer, the transistor, has been created in a living biological system for the first time.
The biological transistor, termed the 'transcriptor', acts as a switch that produces an 'on' or 'off' signal. This works by using enzymes known as integrases to control the movement of a protein across short strands of DNA.
The breakthrough is significant as it brings researchers one step closer to building a biological computer. Professor Drew Endy of Stanford University, USA and senior author of the paper, said: 'Biological computers can be used to study and reprogram living systems, monitor environments and improve cellular therapeutics'.
Transistors represent one of three components essential in creating a programmable biological computer. The other two elements, data storage and data transmission, were shown to be possible using biological molecules by the same group last year (reported in BioNews 658).
By carefully combining the transcriptors within the bacterium E. Coli, the scientists were able to create systems known as Boolean logic gates. These gates allow input signals to be processed into different output responses, giving them the potential to be programmed to monitor or affect the cells in which they operate. As with electronic transistors, transcriptors also allow amplification of signals, which is vital in computing.
'We have repurposed a group of natural proteins, called integrases, to realise digital control over the flow of RNA polymerase along DNA, which in turn allowed us to engineer amplifying genetic logic', said Professor Endy.
While the study was conducted in bacteria, it is hoped that biocomputers will be able to function in any living organism, including humans. The researchers were therefore precise in their selection of enzymes. 'The choice of enzymes is important', explained Dr Jerome Bonnet, lead author of the study. 'We have been careful to select enzymes that function in bacteria, fungi, plants and animals, so that biocomputers can be engineered within a variety of organisms'.
While biological computing, or 'biocomputing', is still in its infancy, it is hoped that biocomputers may be one day used to monitor disease.
Dr Bonnet said: 'You could test whether a given cell had been exposed to any number of external stimuli - the presence of glucose and caffeine for instance. [Logic] gates would allow you to make the determination and store that information so you could easily identify those which had been exposed and which had not'.
The research was published in the journal Science.