CRISPR vs. CRISPR - how mobile CRISPR-Cas systems interact with and sometimes replace host systems

• Applicant: Professor Dr. Uri Gophna, Ph.D.
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms ; Microbial Ecology and Applied Microbiology
• Term: since 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 405782890

CRISPR-Cas systems are microbial immune systems that use immune memory that is encoded on DNA spacers in specific places in the genomes termed CRISPR arrays to identify and destroy mobile genetic elements, such as viruses. However, paradoxically, many CRISPR-Cas systems, in both bacteria and archaea, are themselves encoded on mobile genetic elements. This can lead to a conflict when the CRISPR-Cas-containing mobile element enters a cell that already has a pre-existing CRISPR-Cas system. Such conflicts in archaea can occur even between systems from the same type, which can then use each other's CRISPR arrays for their activity. Compatibility between two systems in the same cell can then result in some level of redundancy, which could end up in a loss of one set of the CRISPR-associated (cas) genes while retaining the precious immune memory acquired by both systems (their CRISPR arrays). In this proposal we will experimentally test scenarios of conflicts between CRISPR-Cas systems, and the ability of a surviving system to utilize the arrays left behind by the one that was lost. We will recreate CRISPR-Cas invasion events in the lab and follow the dynamics of CRISPR-cas conflicts using experimental evolution. This will be performed using a natural CRISPR-Cas encoding archaeal virus that is integrated into the genome of Haloferax lucenetense strain that also has an additional CRISPR-Cas system encoded elsewhere in its genome.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2141: Much more than defence: the multiple functions and facets of CRISPR-Cas
• International Connection: Israel