E. coli Killer - Microbiologists have found a natural predator of dangerous E. coli, a bacteria-eating virus. (6/3/03) Lysins To Kill - A new way to fight dangerous bacteria, including things like deadly anthrax, pits nature against nature. (2/11/03) Exploding Anthrax - There’s a new weapon in the war against anthrax, and it can both detect it quickly and kill it. (8/21/02) The Phage Forum Silent Killers: Fantastic Phages? Genetics researchers have discovered a new source of infectious disease. As this ScienCentral News video reports, they say viruses that were thought to be harmless to humans can actually spread disease. Dangerous Phage A virus that can target and attack bacteria could be a lifesaver. But what if it changes that bacteria into something even more harmful? Writing in the July 2003 issue of Infection and Immunity , researchers at Rockefeller University report that viruses called bacteriophages can cause the bacteria inside our bodies to acquire harmful new genes. Scientists have long said bacteriophages are harmless to humans because specific phages only infect specific types of bacteria. Indeed, using the viruses to treat or prevent disease is a hot area of research . "But we are now understanding more about what they can do," says Vincent Fischetti , professor and head of the Laboratory of Bacterial Pathogenesis at Rockefeller University. "We now find that these bacterial viruses are able to infect bacteria that are found in the normal body and cause those organisms to change." A bacteriophage, or phage for short, survives by reproducing inside bacteria cells. A phage injects its DNA into a host bacterium, and then enters its active, or "lytic" mode, when it reproduces the DNA inside the bacterial cell. Then it bursts (or "lyses") the bacterium , and releases the extra phages that grew inside it. But phages have another strategy that allows them to hide inside the host cell and wait for an opportunity to infect other bacterial hosts. In this mode (the "lysogenic" phase) instead of multiplying right away, the phage's DNA can insert itself into the bacteria's chromosome. This gives the bacterium new genes. "So while bacteria can be infectious," says Fischetti, "bacterial viruses in many ways can also be infectious by carrying characteristics such as scarlet fever… so all you need to do is acquire the virus to convert bacteria that you may carry in your oral cavity or in your gut, to transform those organisms into the disease-producing organisms." Fischetti says this wasn't understood before because scientists didn't know how the viruses behave inside the body. To study this, they used mice with strep bacteria in their throats. When they added strep bacteria infected with a phage virus that carried the gene for the toxin that causes scarlet fever, the virus came out of hiding and converted the strep throat bacteria to scarlet fever-producing strep. "We actually proved that the viral gene moved from one bacterium to the second bacterium," Fischetti says. The next experiment they performed was to determine whether this could all occur with just the bacterial virus. They exposed the strep bacteria in the mouse throat to just the toxin-producing virus, and found that the virus alone could cause them to make the toxin. Since these viruses get activated inside the body, Fischetti says they could also turn the harmless bacteria that live in our throats or intestines against us. "We're assuming that these same events can occur in humans, since we carry these same bacteria, and the same viruses can also interact with the oral cavity or the gut of humans," Fischetti says. He now wants to know how much human disease transmission the viruses account for. "All of scarlet fever is due to this toxin," he says. "The real question is what do you acquire? Do you acquire the organism or do you acquire the phage that transforms the organism in your oral cavity?" Other bacterial diseases that are caused by toxins that can be carried by bacteriophages include diphtheria, cholera, and E. coli poisoning. Phages "obviously play a r

joyce gramza, vincent fischetti, rockefeller university.,