Every time we make a call, send a text message or watch a video, some of the energy stored in the cell phone battery is depleted. Living cells also store energy in “currencies” they can cash in when needed, in order to fuel life processes. The main energy currency of all living things on Earth – the lithium battery that powers the living world, as it were – is a molecule known as ATP. But even though charging cells with ATP molecules is of vital importance, it has now been discovered that discharging them could be no less crucial and even lifesaving. In a study published today in Cell, researchers from the Weizmann Institute of Science have described a new family of proteins that deplete cells of their energy, thereby protecting the cells from invaders. The scientists showed that this previously unknown immune mechanism does not exist only in single-celled organisms. It has been preserved through more than a billion years of evolution and is used by many living creatures, from corals to bees.
The newly revealed strategy is the latest of more than 100 recently discovered sophisticated mechanisms used by bacteria in their heroic battle against phages, the viruses that attack bacteria. Many of these mechanisms were discovered and described in the laboratory of Prof. Rotem Sorek of Weizmann’s Molecular Genetics Department. Just like the viruses that attack us, phages are also made up of a small quantity of proteins and a lot of genetic material – DNA or RNA – which they inject into the bacteria they are taking over. Having accomplished this task, these viruses use the bacteria’s cellular machinery to replicate themselves over and over. When they have depleted a single bacterium’s resources, they tear down its membrane, break out and spread throughout the entire bacterial colony.