Washington, Feb 28 : Research has now exposed the predatory instincts of a virus, one that hijacks the cholera bugs' immune system.

The bacteriophage (virus infecting and replicating within bugs), called phage in short, turns the hijacked system to disable the cholera bugs' defence mechanism so that they can replicate and kill more cholera bugs.

This discovery by a team led by Andrew Camilli, professor of molecular biology and microbiology from Tufts University School of Medicine, could open the way to effective targeting of superbugs, which are extremely resistant to current antibiotics, the journal Nature reports.

Until now, scientists thought phages existed only as primitive particles of DNA or RNA and therefore lacked the sophistication of an adaptive immune system, which can respond rapidly to a nearly infinite variety of new challenges, according to a Tufts University statement.

Each phage is parasitically mated to a specific type of bacteria. This study focused on a phage that attacks Vibrio cholerae, the bacterium responsible for cholera epidemics in humans.

Camilli said: "The study lends credence to the controversial idea that viruses are living creatures."

Kimberley D. Seed, postdoctoral fellow in Camilli's lab, was analysing DNA sequences of phages taken from stool samples from patients with cholera in Bangladesh when she identified genes for a functional immune system previously found only in some bugs.

They next infected the same strain of cholera bug with phage harbouring the immune system, and observed that the phage rapidly adapted and thus gained the ability to kill the cholera bacteria.

"Virtually all bacteria can be infected by phages. About half of the world's known bacteria have this adaptive immune system, called CRISPR/Cas, which is used primarily to provide immunity against phages," said Seed. (IANS)