October 28, 2011 10:09 pm

How bacteria may power computers

A biological computer has taken a step from science fantasy toward reality at Imperial College London

A biological computer, in which the basic components are made from bacteria rather than silicon circuitry, has taken a step from science fantasy toward reality at Imperial College London.

Researchers there have built “logic gates”, the basis of digital information processing, from genetically engineered E. coli, the bacteria that populate the human gut. These are the first biological logic gates proven to function like electronic ones.

“Logic gates are the fundamental building blocks in silicon circuitry that our entire digital age is based on,” says Richard Kitney, professor of biomedical systems engineering at Imperial. “Without them, we could not process digital information.

“Now that we have demonstrated that we can replicate these parts using bacteria and DNA, we hope that our work could lead to a new generation of biological processors, whose applications in information processing could be as important as their electronic equivalents,” Kitney says.

The Imperial team suggests that bacterial logic gates could form the building blocks of microscopic biological computers – although these are still many years away.

Possible applications include sensors that swim inside arteries, detecting the build-up of harmful plaque and rapidly delivering medications to the affected zone, and sensors that detect and destroy cancer cells inside the body.

In a paper in the journal Nature Communications, the scientists describe how they transferred two linked regulatory genes from Pseudomonas syringae, a bacterium that infects plants, into E. coli.

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These genes are activated separately by organic chemicals, such as sugars – and both need to be switched on at the same time to produce a biological response in the bacteria. By appropriate chemical stimulation, the scientists made them respond just like an “AND gate” in a digital circuit. They went on to make a “NOT gate” and, by combining them, the more complex “NAND gate”.

Formidable practical problems remain in deciding how to connect many individual bacterial components together into a working system. As living cells, they cannot be wired together like electronic components. They will probably need to be immobilised by encapsulation in some sort of micro-fluidic device, says Martin Buck, the biology professor on the Imperial team.

“We believe that the next stage of our research could lead to a totally new type of circuitry for processing information,” Buck says. “In the future, we may see complex biological circuitry processing information using chemicals, much in the same way that our body uses them to process and store information.”

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Voters opt for the ‘big man’ politician

The “caveman” theory of political popularity – that physically formidable men are most appealing to voters – is rooted in evolutionary psychology, according to a study by political scientists at Texas Tech University.

Barack Obama

“Some traits and instincts that may have been acquired through evolution continue to manifest themselves in modern life,” says Gregg Murray, co-author.

Previous analysis of US presidential elections over two centuries has shown candidates are taller than the adult male population as a whole – and the taller of the two major party candidates has won the popular vote two-thirds of the time. A similar “big man” concept existed in many traditional societies.

The Texas research, published in Social Science Quarterly, involved 467 university students in two studies. In the first, participants were asked to describe and draw a figure that represented their idea of a “typical citizen” and an “ideal national leader”. In 64 per cent of cases the leader was taller.

Then the students answered questions on their own leadership attributes. For men there was a strong association between an individual’s height, his perception of his own leadership capability and his interest in running for political office; among women the link was much weaker.

“Culture and environment alone cannot explain how a preference for taller leaders is a universal trait we see in different cultures today,” says David Schmitz, co-author. “Our research and the literature demonstrate that there is a preference for physically formidable leaders that likely reflects an evolved psychological trait, independent of any cultural conditioning.”

In the 2008 race for president, the 6ft1in Barack Obama towered over 5ft8in John McCain.

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Plants manipulated to survive under water

Prolonged flooding has a catastrophic effect on agricultural crops – most plants cannot survive for long under water because they are starved of the oxygen they require for respiration.

Now a scientific collaboration between Nottingham University and the University of California, Riverside, has identified the molecular mechanism that some plants use to detect and defend themselves against low oxygen levels. The discovery, reported in the journal Nature, could eventually lead to more flood-tolerant crops.

Arabidopsis

The cress-like plant Arabidopsis

“The mechanism controls key regulatory proteins called transcription factors that can turn other genes on and off,” says Michael Holdsworth, professor of crop science at Nottingham. “It is the unusual structure of these proteins that destines them for destruction under normal oxygen levels, but when oxygen levels decline, they become stable.”

The proteins’ stability leads to changes in gene expression and metabolism that enhance survival in the low oxygen conditions caused by flooding. When the plants return to normal oxygen levels, the proteins are again degraded, providing a feedback control mechanism.

By genetic manipulation of the pathway, the scientists were able to increase plants’ tolerance of low oxygen levels and flooding.

They were working with Arabidopsis, a cress-like plant, but Julia Bailey-Serres, of UC Riverside, says, “there is no reason why these results cannot be extrapolated to other plants.”

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X-ray vision now a possibility for soldiers

Engineers at Massachusetts Institute of Technology have developed radar technology to see through thick concrete or brick walls – which could give soldiers in urban warfare the equivalent of X-ray vision.

The prototype system can detect people moving behind eight inches of concrete from 20ft away. At present they just look like “blobs” on a video screen but the MIT researchers expect soon to have a more user-friendly display that will show recognisable images.

The technology uses microwave transmitters and receivers, like conventional radar. It is ultra-sensitive, because the signal is reduced to 0.0025 per cent of its original strength after the microwaves have passed through the wall, bounced off any objects there and travelled back through the wall to the receiving antennae.

Although the system can only detect objects in motion, a living human cannot avoid moving enough to be seen – even when trying to stay still.

Gregory Charvat, the MIT project leader, says the technology was developed primarily with military applications in mind. “This is meant for the urban war fighter … those situations where it’s very stressful and it’d be great to know what’s behind that wall,” he says.

Future work will include mounting the system on a vehicle and testing it on a variety of walls and buildings.

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