Deciphering and shaping bacterial diversity through CRISPR

Phage and bacteria have engaged in a sustainable arms race, a seemingly endless conflict, since the beginning of time. CRISPR-Cas systems shape and generate environmental diversity through evolution of both predator and prey genomes. Indeed, the gain or loss of CRISPR-mediated immunity and genome maintenance can spark speciation in bacteria. Alternatively, turning CRISPR-Cas on the host by targeting chromosomal DNA has led to the development of next-generation smart antimicrobials and genetic screening and engineering technologies. Although the ability to target and cleave DNA in a sequence-specific manner is a powerful mechanism utilized by bacteria to fend off phage, plasmids, and potentially harmful nucleic acids, it is also a promising technology for programmable targeting of undesirable bacteria in microbiome consortia.