CRISPRs have taken microbiology by storm in the last few years. If you haven’t caught up yet, there’s a short introductory primer here. CRISPRs (or CRISPR-Cas systems as they are now tending to be called) protect bacteria from infection by bacteriophages and other mobile genetic elements including plasmids. Because they are barriers to horizontal gene transfer, CRISPRs reduce the speed of eviolution of pathogens. but CRISPRs can increase also virulence by modulating gene expression. A recent short review discusses the “love-hate relationship between bacterial pathogens and their CRISPR-Cas systems“.
Impact of CRISPR immunity on the emergence and virulence of bacterial pathogens. (2014) Current Opinion in Microbiology, 17, 82-90.
CRISPR-Cas systems protect prokaryotes from viruses and plasmids and function primarily as an adaptive immune system in these organisms. Recent discoveries, however, revealed unexpected roles for CRISPR loci as barriers to horizontal gene transfer and as modulators of gene expression. We review how both of these functions of CRISPR-Cas systems can affect the emergence and virulence of human bacterial pathogens.