Cracking CRISPR

Courtesy of Philippe Horvath

R. Barrangou et al., "CRISPR provides acquired resistance against viruses in prokaryotes," Science, 315:1709–12, 2007. (Cited in 66 papers)

Using the bacterium Streptococcus thermophilis, a team led by Philippe Horvath at the Danish food ingredient company Danisco, integrated bacteriophage sequences into "clustered regularly interspersed short palindromic repeat" (CRISPR) regions to generate phage-resistant bacterial strains. "They directly confirmed the prediction," says Eugene Koonin, a computational biologist at the US National Center for Biotechnology Information.

Koonin, together with John van der Oost at Wageningen University in the Netherlands, reconstituted the CRISPR phenomenon in Escherichia coli, and showed that a complex of CRISPR-associated (Cas) proteins cleaves a CRISPR RNA precursor, leaving only the virus-derived sequence, which then interferes with phage proliferation (Science, 5891:960–4, 2008).

Danisco is exploiting the CRISPR mechanism to improve the antiviral immunity of the bacterial cultures used to make yogurt and cheese. "We are trying to vaccinate the bacteria against a broad range of phages," says Horvath. "We end up having a superstar culture" that is highly resistant to phage attack, adds Rodolphe Barrangou, the study's lead author.

Erik Sontheimer and Luciano Marraffini of Northwestern University showed that CRISPR sequences can impede the spread of antibiotic resistance by blocking the transfer of plasmids between Stapholococcus species (Science, 322:1843–5, 2008).