Electron micrograph of bacteria-infecting viruses
Bacteria sometimes commit suicide for the good of the group. When a virus infects a bacterium, the cell kills itself rather than allow the virus to replicate inside it and spread to the surrounding bacteria.
The way this works is that when viruses aren’t around, the bacteria manufacture both a bacterial cyanide pill—a toxin molecule they could use to wipe themselves out if they come under attack—and an antitoxin molecule that keeps the toxin in check. When a virus infects the bacterium, the toxin is released, kills the bacterial cell, and prevents the virus from spreading to other cells. It’s bad for the individual bacterial cell but good for the community—and certainly bad for the infecting virus. Now researchers have found a virus that manipulates this mechanism for its own means, saving itself by keeping its host bacteria from cellular suicide.
Where viruses and bacteria cause cancer
Strictly speaking, cancer is not contagious. But a fair number of cancers are clearly caused by viral or bacterial infections: lymphomas can be triggered by the Epstein-Barr virus, which also causes mononucleosis. Liver cancers can be caused by Hepatitis B and C. Cervical cancers can be caused by human papillomavirus, the major reason behind the development of a vaccine against it. For some of these cancers, nearly 100% of the cases have an infectious link—when researchers check to see if a virus or bacterium is working in the tumor or has left signs of its presence in a patient’s blood, the answer is nearly always yes.
A new paper in The Lancet takes a look at the very best data on the prevalence of infection-caused cancers and comes up with some striking numbers. Overall, they estimate that 16% of cancer cases worldwide in 2008 had an infectious cause—2 million out of 12.7 million.
What’s the News: Infections that change an organism’s personality are a strange little corner of biology, with toxoplasmosis, which brainwashes mice and rats to have no fear of cats, topping the list. But scientists think that more pedestrian infections could play a role in shaping personality, especially when they happen early in life. Ducklings provide the latest data that this theory may have something to it.