Scientists have discovered that bacterial cells may have their own version of a viral “memory”. In complex multicellular organisms (like us), our immune system uses specialized memory cells that can help detect dangerous invaders (like viruses) once our bodies have come into contact with them – these memory cells are what vaccines aim to create in our bodies without making us sick.
Bacterial cells can also fall victim to viruses, which we call phage. Phage look like an alien space craft and their behavior is very alien-like… they attach to the bacterial cell wall, “impregnate” the bacterial cell with their genetic information (Aliens with Sigourney Weaver anyone?), and force the cell to make more of the virus – creepy!
Now we know of an ingenious method bacterial cells use to fight back.
For some time, scientists have known about small repeating chunks of DNA within bacterial chromosomes that seem to help prevent the infection of phage, which they've dubbed "CRISPR" (clustered regularly interspaced short palindromic repeats). But how do they prevent phage infection? Turns out, when viruses "impregnate" bacterial cells with their genetic information, some types of bacteria have incorporated chunks of these viral genes into their own genomes. When that same virus attempts to infect the bacterial cell again, these "memory genes" recognize the viral genetic information as BAD and send out little proteins that act like scissors, cutting up the foreign DNA, in much the same way that our own immune systems tackle viruses once we've been vaccinated.
Could this be a snapshot into the past of the evolution of our very own immune systems?
Vale, P.F., Little, T.J. (2010). Review. Bacteria-phage coevolution.
