High-MOI Induces Rapid CRISPR Spacer Acquisition in from an Deficient Virus

Spacer acquisition, the first step in CRISPR-Cas adaptive immunity, plays a critical role in establishing and strengthening host defense against mobile genetic elements (MGEs). Here we present a host-virus system, where an increase in the multiplicity of infection (MOI), of a CRISPR-Cas susceptible virus, forces rapid spacer acquisition in the LAL14/1 CRISPR arrays. Spacer acquisition was observed as early as 30 minutes post infection, with the newly acquired spacers uniformly distributed across the genome of the virus. Although the newly acquired spacers were predominantly effective only against the CRISPR-Cas susceptible mutant virus, we were able to isolate a host mutant with a novel spacer which provides immunity against the multiple Acr encoding wildtype virus, rod-shaped virus 2 (SIRV2).