Cracking CRISPR

Credit: Courtesy of Philippe Horvath The paper: R. Barrangou et al., "CRISPR provides acquired resistance against viruses in prokaryotes,"

By | March 1, 2009

<figcaption> Credit: Courtesy of Philippe Horvath</figcaption>
Credit: Courtesy of Philippe Horvath

The paper:

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

The finding:

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.

The follow-up:

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).

The application:

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.

The extension:

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).

Sensitivity to phage (measured by plaque efficiency)*
Wild-type Streptococcus: 1.0
Wild-type with one phage spacer: 1.8 x 10-5
Wild-type with two phage spacers: <10-7
*J Bacteriol, 190:1390-1400, 2008

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