WASHINGTON - US scientists said they have taken an important step toward making an artificial life form by making a ribosome - the cell's factory.

The ribosome makes the proteins that carry out key business for all forms of life. Messenger RNA carries DNA's genetic instructions to a cell's ribosome, which then cooks up the desired protein. Every living organism from bacteria to humans uses a ribosome, and they are all strikingly similar.

It is not quite artificial life, but an important step in that direction, said George Church, a professor of genetics at Harvard Medical School, who directed the research with a single graduate student.

'If you going to make synthetic life that is anything like current life ... you have got to have this ... biological machine,' Prof Church told reporters in a telephone briefing.

And it can have important industrial uses, especially for manufacturing drugs and proteins not found in nature.

Prof Church stressed his research has not been published in a scientific journal, the usual route for reporting such work. He presented it over the weekend to a seminar of Harvard alumni.

Prof Church's group is not seeking to make life in a test tube, but instead to make designer proteins in lab dishes.

'We can ... go straight into protein synthesis,' he said.

Prof Church and post-doctoral fellow Mike Jewett have already synthesised firefly luciferase - the glowing stuff.

'We'd also like to make a whole new kind of cell ... which is a mirror image of a replicating system.' Most life forms are 'right-handed' or 'left-handed', a quality called chirality. -- REUTERS