To paraphrase Star Trek medic Dr James McCoy: it's life, Jim, but not as we know it. It's obviously intelligently designed.

Professor Chris Voigt's living inventions include microorganisms programmed with DNA-coded logic and operational circuits. He has equipped bacteria with genetic machinery to synthesise and secrete super-strong spider silk, and developed bacterial compounds to seek out, invade and destroy cancers.

Voigt's laboratory at the University of California, Berkeley, is at the forefront of a new era in genetic engineering, an era that goes far beyond simple one- or two-gene additions or deletions. He and his co-workers are collecting a constructor kit of genes from many different species, and interconnecting them to perform complex, multi-stage biosynthetic processes. They use accelerated mutation to boost their output, and recombination to fine-tune the function of their proteins.

Voigt, a plenary speaker at this year's Lorne Conference on Protein Structure and Function, predicts that within two decades, biotechnologists will be custom-designing microbes from scratch, to synthesise industrially valuable products or perform tasks like bioremediation or carbon sequestration.

It's not blue-sky dreaming - Voigt says some projects, like the Salmonella bacteria that spin spider silk, are "going pretty well", and are approaching commercialisation.

Voigt and his colleagues started out with what they describe as 'toy tricks' - for example, bacteria that synthesise compounds that darken on exposure to light. A bacterial lawn on an agar plate can then be used to take a photograph when light is shone on it through a mask-type negative.

Another trick is to insert a genetic logic gate in the gene circuits that detects edges between light and dark, sharpening the image. Similar circuits can be designed to perform logical operations and simple calculations, to enhance control of synthesis processes.

Like industrial production lines, synthesis processes must be performed in a set sequence, so the biochemical circuits also require inbuilt timers.

The Berkeley team has now moved on to more complex and practical applications, like the spider-silk project.

"Our idea was to program the bacteria to perform a series of processes, in much the same way that assembly lines build complex products, to make fibres out of spider-silk proteins," Voigt says.

"We've given the bacteria the ability to make spider-silk proteins, put them into the growth medium, and cut the fibres to form threads. We can encode all these steps in the same cell."

Although the resilient silk of a species like the golden orb spider, Nephila, which is stronger than Kevlar, might seem ideal for weaving a super-strong, lightweight fabric, Voigt's team has refined natural selection's handiwork for a novel medical application: making new arteries.

"With gene-synthesis technology, we don't need to go out into the wild and collect spiders for their silk genes," he says.

"We use databases to search for silk genes from spiders around the world, and recombine selected sequences to create synthetic genes for silks with the properties we want."

The beauty of spider silk, he says, is that it is non-immunogenic in the human body, and combines great strength, low mass, durability and elasticity. It looks an ideal material for replacement arteries. Synthetic arteries must be compliant - capable of stretching and contracting to accommodate sudden, large pressure changes as the heart beats.

Genes for human proteins can also be inserted into silk-gene sequences to add functionality - for example, to enhance colonisation by human cells.