A giant hairy virus which was found in a cooling tower in Bradford has surprised scientists by possessing genetic machinery once thought only to belong to higher life forms, it emerged today.

French researchers made the discovery after mapping the genetic blueprint of "Mimivirus" - a viral whopper the size of a bacterial cell.

They found that Mimivirus broke the rules and blurred the usual line between viruses and cellular organisms.

Shipley microbiologist Dr Tim Rowbotham was working for Leeds Public Health Laboratory, in 1992, when he first found the unusual material in a small industrial cooling tower during a Legionnaires' disease scare in the city.

He named the infected cells Bradfordcoccus and saved them in his freezer for six years before sending them to French researchers.

Now working as an iron monger, Dr Rowbotham said: "I knew it was something special. I'd never seen anything like this before."

He added: "We were originally looking for Legionella bacterium, which grows in amoebae. Legionella is a curved rod shape. But when we got this a under the microscope it was a sphere. "

Dr Rowbotham had hoped to carry out the research himself but, after he took an early retirement, passed the samples to a former colleague who was working with the French team.

He said: "I gave it to the French so they could continue the work and they've done a great job.

"They have sequenced its whole genetic make-up."

One of the defining characteristics of viruses is that they cannot make proteins independently. Instead they have to harness the genes of the host they infect.

But Mimivirus, which is not known to cause human disease, contains a number of genes for protein translation.

It also contains genes for DNA repair enzymes, "heat shock" proteins that respond to stress, and enzymatic pathways all thought to be trademarks of cellular life.

The researchers, led by Didier Raoult of the CNRS research facility at the University of the Mediterranean in Marseilles, wrote in the journal Science: "The size and complexity of the Mimivirus genome challenges the established frontier between viruses and parasitic cellular organisms."

Last year Dr Raoult's team reported the discovery of Mimivirus in amoebae growing in the water of the Bradford hospital's cooling tower.

Mimivirus appears to represent a new family of large "nucleocytoplasmic" DNA viruses that emerged early in evolution.