CRISPR as Bacterial Immune System
Bacteria store short snippets of virus DNA in their own genome and use them to recognise and cut that virus next time; this natural defence was later turned into the CRISPR gene-editing tool.
Open in the interactive tree →Odd repeating DNA stretches were first spotted in E. coli in 1987 (Ishino), and in 2005 several groups found that the spacers between the repeats match the DNA of viruses. In 2007 Rodolphe Barrangou, Philippe Horvath and colleagues at the company Danisco showed in the dairy bacterium Streptococcus thermophilus that adding a virus snippet made cells resistant to that virus and removing it took the resistance away. In 2012 Jinek, Doudna and Charpentier showed that the cutting protein Cas9 can be aimed at any chosen DNA sequence, which turned this defence into the gene-editing tool honoured with the 2020 Nobel Prize in Chemistry.
Prerequisites
- Viruses Discovered1892-1898The stored DNA snippets record past virus attacks on bacteria.
- Genetic Engineering1973Adding and removing virus snippets in bacteria used gene-engineering methods.
- Human Genome Project & Sequencing2003The odd repeats were first noticed in sequenced bacterial genomes.
Unlocks
- CRISPR Gene Editing2012Cas9, the cutting tool of CRISPR editing, was taken from this bacterial defence.