Scientists have turned inanimate chemicals into a living organism in an experiment that raises profound questions about the essence of life.

Craig Venter, the US genomics pioneer, announced last night that scientists at his laboratories in Maryland and California had succeeded in their 15-year project to make the world's first “synthetic cells” – bacteria called Mycoplasma mycoides.

“We have passed through a critical psychological barrier,” Dr Venter told the Financial Times. “It has changed my own thinking, both scientifically and philosophically, about life and how it works.”

The bacteria's genes were all constructed in the laboratory “from four bottles of chemicals on a chemical synthesiser, starting with information on a computer,” he said.

The research – published online by the journal Science – was hailed as a landmark by many independent scientists and philosophers.

Julian Savulescu, ethics professor at Oxford University, said: “This is a step towards . . . creation of living beings with capacities and natures that could never have naturally evolved.”

The synthetic bacteria have 14 “watermark sequences” attached to their genome – inert stretches of DNA added to distinguish them from their natural counterparts. They behaved and divided in lab dishes like natural bacteria. M mycoides was chosen as a simple microbe with which to develop and prove the technology. It has no immediate application.

But scientists at the J Craig Venter Institute and Synthetic Genomics, the company funding their research, intend to move on to more useful targets that may not exist in nature. They are particularly interested in designing algae that can capture carbon dioxide from the air and produce hydrocarbon fuels.

Last year Synthetic Genomics signed a $600m agreement with ExxonMobil to make algal biofuels. “We have looked hard at natural algae and we can't find one that can make the fuels we want on the scales we need,” Dr Venter said.