The research opens the way for scientists to create new life forms that can be genetically programmed to carry out a variety of functions, such as producing carbon-free fuel or made-to-order vaccines and providing new forms of food and clean water. However, the study also raises ethical concerns about the technology falling into the wrong hands, and, for instance, being used to make biological weapons, or by scientists to "play God" with life.
The research team, led by Craig Venter, who previously directed one of the teams which decoded the human genome, said they had created synthetic life in the form of a new species of bacteria that operates entirely under the control of a man-made set of genetic instructions, originally stored on a computer. They synthesised the genome of a bacterial cell and used it to "boot up" the empty cell of another species of bacteria, which then replicated freely as if it were carrying its own set of genetic instructions instead of a set made in a laboratory.
"This is the first synthetic cell that's been made, and we call it synthetic because the cell is totally derived from a synthetic chromosome, made with four bottles of chemicals on a chemical synthesiser, starting with information in a computer," Dr Venter said.
"We start with a living cell but the synthetic chromosome totally transforms that living cell to this new synthetic cell," he added.
Dr Venter dreamed of creating artificial life 15 years ago when he led a study that produced the first decoded genome of a microbe. After years of trying to work out the minimal set of genes necessary for life, and many more years trying to overcome the technical difficulties of constructing an entirely artificial genome, he has finally succeeded in realising his vision.
"This is both a baby step and a giant step. It's a giant step because, until this was done, it was only hypothetical that it could work. It's a baby step in terms of all the distance we have to go before you can buy fuel made from carbon dioxide or have new medicines or new sources of food," Dr Venter said.
"It's a new enabling technology, but it tells you as much about the definition of life as anything else. We consider it a philosophical leap, being able to start with information in the computer, build the chromosome chemically and have it active. That has never been done before. It has changed my definitions of life and how dynamic it is – simply by putting new software into the cell, the cell starts producing the new proteins coded for by that software and creates a new cell. So life is much more dynamic than most people envision and the dynamic process is totally controlled by the software of life, which is the DNA," said Dr Venter.
Some ethicists, however, expressed concerns. "Venter is not merely copying life artificially ... he is going towards the role of a god – creating artificial life that could never have existed naturally," said Professor Julian Savulescu, an ethicist at the University of Oxford.
Professor John Harris, an expert on biomedical ethics at Manchester University, said: "This is heady stuff which Venter admits has powerful potential for both good and ill. While Venter is very precise about the possible benefits he is not specific about the dangers. This work deserves enthusiasm, but only so long as the risks are given attention commensurate with the benefits."
The milestone, published in the journal Science, was achieved by a team of 24 scientists at the J Craig Venter Institute in Rockville, Maryland. They received $40m (£28m) funding. Some came from the US Department of Energy, some from drug companies interested in new ways of making vaccines and other pharmaceuticals and from oil companies keen to develop new sources of energy.
The scientists used the published genome of a microbe called Mycoplasma mycoides to construct their own synthetic version in the form of a circular chromosome made of a molecule of DNA composed of a sequence of 1,080,000 "letters" of the four-letter genetic alphabet; this was stitched together from shorter fragments made in a laboratory "gene machine".
The researchers then placed this synthetic chromosome into the cell of another species of bacterium, M. capricolum, which had had its own chromosome removed. After months of trial and error – when one mistake in the million letters led to a three-month delay – the scientists managed to "boot up" these empty cells so that the M. capricolum cells replicated normally, but without any of its own genes or proteins and only with those of M. mycoides.
Scientists in Britain applauded the achievement as one of the most important moments in genome research. "[It] is a landmark study that represents a major advance in synthetic biology," said Professor Paul Freemont of Imperial College London, co-director of the Centre for Synthetic Biology.
"This now provides a 'proof of concept'. The applications of this enabling technology are enormous and one might argue this is a key step in the industrialisation of synthetic biology leading to a new era of biotechnology," he added. Professor Douglas Kell, chief executive of the Biotechnology and Biological Sciences Research Council, said the study was an important step in the development of a new area of science. "Synthetic biology is a relatively new field and within the global research community there is some truly avant-garde science happening."
However, other commentators condemned the work, claiming that it is being promoted with unrealistic expectations and could end up creating more problems than it can solve.
"What is really dangerous is these scientists' ambitions for total control over nature, which many people describe as 'playing God'. The claim of authorship of nature goes hand-in-hand with the claim to monopoly patent rights over it," said David King of Human Genetics Alert.
"Scientists' understanding of biology falls far short of their technical capabilities. We have already learnt to our cost the risks that gap brings, for the environment, animal welfare and human health," Dr King said.
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