Craig Venter has been working for years on a man-made organism

Dr Craig Venter, the man who led the private sector effort to sequence the human genome, has been working for years to create a man-made organism.

But constructing a primitive microbe from a kit of genes is a daunting task.

Dr Venter says, eventually, these life forms could be designed to make biofuels and absorb greenhouse gases.

The publication of the patent application has angered some environmentalists.

The Canada-based ETC group, which monitors developments in biotechnology, called on patent offices to reject applications on synthetic life forms.

The J Craig Venter Institute's US patent application claims exclusive ownership of a set of essential genes and a synthetic "free-living organism that can grow and replicate" made using those genes.

It has also filed an international application at the World Intellectual Property Organization (WIPO) which names more than 100 countries where the institute may seek monopoly patents.

'Gene kit'

Dr Venter's team intends to construct an organism with a "minimal genome" that can then be inserted into the shell of a bacterium.

By removing genes, one by one, from a bacterium called Mycoplasma genitalium they identified the minimum number of genes required for this particular organism to replicate, or reproduce, in its controlled environment.

They have been able to remove 101 of its 482 genes without killing the bacterium, meaning that 381 were required for replication.

But generating a man-made living organism from the bottom up requires much more than just its minimal genome.

For example, in order to get the genes to do something, there have to be chemicals to translate the genes into messenger RNA and proteins.

Scientists around the world have been wrestling with the task of generating a so-called free-living synthetic organism for years.

Environmental objection

The ETC Group says it will be writing to Dr Venter asking him to withdraw his institute's patent applications.

"We don't want to engage in a long-term legal strategy to slap down bad patents. These patents must be struck down before they're issued," said Hope Shand, a spokesperson for the group.

Jim Thomas, of ETC Group, added: "These monopoly claims signal the start of a high-stakes commercial race to synthesise and privatise synthetic life forms."

It said the company was pressing ahead with its work despite the fact the public had not had the chance to debate the "far-reaching social, ethical and environmental implications".

Dr Venter maintains that artificial life forms could produce solutions to global problems such as green sources of fuel and climate change.

The effort could result in "designer microbes" that produce biofuels such as ethanol, and hydrogen.

They could also be engineered to remove carbon dioxide (CO2) and other greenhouse gases from the atmosphere.

Dr Venter first announced that scientists were working on creating synthetic life forms at a conference in California in 1999.