Biologist Craig Venter and his team replicated a bacterium's genetic structure entirely from laboratory chemicals, moving one step closer to creating the world's first living artificial organism.

The scientists assembled the synthetic genome by stringing together chemicals that are the building blocks of DNA. The synthetic genome was constructed so it included all the genes that would be found in a naturally occurring bacterium.

The research was published in the online version of the journal Science by a team of scientists from the J. Craig Venter Institute in Rockville, Md. The authors include Hamilton Smith, who won the Nobel Prize for Medicine in 1978.

'It's the second significant step of a three-step process to create a synthetic organism,' said Dr. Venter, in a conference call with reporters. The final step could prove far trickier, though Dr. Venter defied his critics and deciphered the human genome with startling speed about eight years ago.

The larger quest is to make artificial life forms with a minimum set of genes necessary for life. It is hoped that such organisms could one day be engineered to perform commercial tasks, such as absorbing carbon dioxide from the air or churning out biofuels.

The scientific challenge of creating synthetic life isn't trivial, nor are the ethical and legal concerns. There is little government oversight, and researchers involved in such experiments regulate themselves. Detractors worry that the lack of safeguards increases the risks that a potentially dangerous man-made organism might run amok. (In creating the artificial genome of Mycoplasma, Dr. Venter's team disrupted the genes that would enable it to infect other organisms.)

Nonetheless, the science is pushing forward at a rapid pace. In June, a Venter-led team published details of an experiment in which it inserted the DNA of one species of bacteria into the cells of another bacteria species. That process almost magically 'booted up' the genome of the donor bacteria, sparking it to life.

The team hopes to use a similar trick to boot up the artificially created genome, to create a man-made living organism. But, Dr. Venter said, 'there are multiple barriers' to achieving that goal.

Dr. Venter now believes that the challenge of creating a synthetic organism is within his grasp. 'I'll be. . . disappointed if we can't do it in 2008,' he said.

美国生物学家克雷格?文特(Craig Venter)以及他带领的研究小组日前完全利用实验室化学物质复制出了一种细菌的基因组，向创造首个人造生命又迈进了一步。

科学家们将实验室化学物质作为脱氧核糖核酸(DNA)的基因块串列在一起，从而合成出了基因组。而人造基因组的基因都可以在天然细菌体内找到与其对应的部分。

这项研究成果由马里兰州克雷格?文特研究院(J. Craig Venter Institute)的一组科学家刊登在《科学》(Science)杂志网络版上。署名作者包括1978年诺贝尔医学奖获得者汉密尔顿?史密斯(Hamilton Smith).

文特在与记者举行的电话会议上表示，创造人造生命的实验分三个阶段，而此次成功标志着第二阶段的完成，但最后这一步的难度会大得多。不过他在大约八年前曾顶住外界异议，以惊人的速度破译了人类基因组。

一个更大的问题在于要让人造生命携带有使其存活下来最起码的基因组。预计此类生物有朝一日能应用在商业领域上，例如吸收空气中的二氧化碳或提炼生物燃料。

广告向人造生命领域发起挑战在科学上面临着不小的难度，而且在伦理和法律方面也有很多问题。目前几乎没有政府对此类研究进行管理，参与实验的研究人员都是依靠自律。而中伤这项研究的人声称，安全保障的缺失将增加人造生命酿成大祸的风险（文特率领的研究小组在合成支原菌基因组时，有意破坏了赋予染色体感染其他生物的能力的基因）。

尽管如此，研究正在迅速向前推进。去年6月，由文特率领的一个研究小组公开了一项实验的详细情况。在这项实验中，他们将一种细菌的DNA移植到另一种细菌的细胞中，并近乎奇迹般的“激活”了被植入的基因组。

研究小组希望采用类似的方法能激活人造的基因组，从而创造出一种人造生命。不过文特表示，在成功的道路上还存在许多障碍。

但文特相信，现在距离大功告成只有一步之遥。他对此表示，如果无法在2008年取得成功……将是一件令人失望的事情。