All animals, plants and bacteria run the risk of being infected by specific viruses. For humans, such viruses include the flu virus, for the tobacco plant this is the tobacco mosaic virus and for the intestinal bacterium E. coli this is the enterobacteria phage lambda.
During the course of evolution, these organisms have developed systems to render viruses harmless. Viruses respond by adapting themselves in such a way that they avoid the defence mechanism, to which the bacteria respond in turn. In short, there is a continuous arms race between bacteria and viruses.
Researchers at Wageningen University, together with colleagues from England and the United States, have unravelled a mechanism with which bacteria can defend themselves for a longer period against threatening viruses. Over the long term, this research offers possibilities to protect bacteria used in industrial processes against viral infections by giving them a 'flu vaccination'.
The mechanism that bacteria use to protect themselves against viruses was discovered last year. In an ingenious fashion, the bacteria build pieces of viral DNA into their own DNA. The 'adopted' segment of DNA works like a snapshot in a photo album, a type of memory that reminds the bacteria during a subsequent encounter with the same virus. At that point, the viral DNA is recognised, after which the bacteria set a system into operation that ultimately leads to the breakdown of the virus. Until recently, the operation of this system was a mystery.
The team of researchers from Wageningen, Sheffield (UK) and Bethesda (USA) succeeded in unravelling the operation of this defence system. In recent years, researchers Stan Brouns, Matthijs Jore, Magnus Lundgren and John van der Oost (Laboratory of Microbiology of Wageningen University) identified six bacterial proteins involved in the defence system.
These proteins help the bacteria use the built-in virus fragment to prevent a virus infection. The researchers determined that one of the proteins cuts the 'virus snapshot' out of the photo album, and together with the other five proteins, compares the snapshot with the DNA of the invading virus. In the same way, other viruses in the photo album can also be rendered harmless.
With this knowledge, it is theoretically possible to protect bacteria against problematic viruses. This can be compared to a flu vaccination for bacteria. Potential applications include industrial fermentation processes, where bacteria that produce a useful substance are protected against viral infection by means of a 'vaccination' . By reversing the process, the protective mechanism of bacteria can also be deactivated. This could lead to a strategy where viruses can be used to combat bacteria that have developed an advanced form of antibiotic resistance, such as the hospital bacteria.
Article: 'Small CRISPR RNAs guide antiviral defense in prokaryotes' is published in Science vol. 321, 960-964, 15 August 2008
