Researchers Find Some Bacteria Attack With Spring Loaded Poison Molecular Daggers

Posted on February 27, 2012

Bacteria Attacking With Molecular Dagger

Bacteria have evolved novel ways to secrete proteins into the fluid around them or into other cells. Researchers at the California Institute of Technology (Caltech) have proposed that one of these methods - the type VI secretion system apparatus - works by shooting spring-loaded poison molecular daggers. The nano-weapon - about 80 atoms long - is a tube that contracts very quickly, firing an inner dagger through the cell's membranes, into the surrounding medium and, possibly, into another cell. The tube then disassembles and can reassemble elsewhere in the cell, ready to fire another molecular dagger.

Grant Jensen, professor of biology at Caltech and coleader of the study, says, "People aren't surprised that animals have really interesting ways to hurt each other-snakes have venom, bears have claws. But they might be surprised that a single cell within one of those animals' bodies is still 100 times larger than the bacterial cells we're talking about, and yet the bacterial cells contain weapons that are so sophisticated. That's the marvel."

The findings, made in collaboration with researchers at Harvard Medical School, appear as an advance online publication of the journal Nature. Using an electron cryomicroscope, the researchers were able to see the "dagger" being constructed, fired and then disassembled. Take a look:

Photo: Nature/Everett Kane