Engineers have found a way to create bacteria that act as tiny computers, processing signals and storing the results in their DNA.
The bacteria, developed at the Massachusetts Institute of Technology (MIT) in the US, are genetically designed to behave like circuits, turning an input signal from the environment into an output, for example producing a protein when a certain chemical is present.
The researchers say their work to enable the cells to also store information could one day allow them to act as environmental sensors, efficient controls for biomanufacturing or as a way to program the way stem cells transform into other cell types.
Scientists have previously been able to create cellular circuits that work in a similar way to conventional electronics using biological equivalents of logic gates, the parts of a circuit that convert a specific input into an output.
The MIT researchers have also been able to produce bacteria that have their genetic code irreversibly altered by enzymes when the input signal is detected, effectively storing information in the cell’s genetic “memory”.
‘Almost all of the previous work in synthetic biology that we’re aware of has either focused on logic components or on memory modules that just encode memory,’ said Timothy Lu senior author of a paper on the research published in Nature Biotechnology.
‘We think complex computation will involve combining both logic and memory, and that’s why we built this particular framework to do so.’
To do this, the scientists designed a bacterium that produced enzymes known as recombinases – which can cut out, reverse or insert stretches of DNA – in response to two input signals.
The enzymes altered the cell’s DNA so that it began producing an output, in this case a green fluorescent protein (GFP). Because the DNA couldn’t be changed back, the cell went on producing GFP even if the input signals disappeared. And if the cell died, the scientists could sequence its DNA and would be able to see that the proteins had altered the genetic code.
These kind of circuits could enable scientists to programme cells to function in a certain way, for example stimulating them with an input chemical that causes them to permanently turn on their protein production, allowing better control over the production of cells that generate biofuels, drugs or other useful compounds.
They could also enable environmental sensors with very precise long-term memory because the DNA remains altered as the cells reproduce over the next 90 generations.