An unexplored facet of CRISPR biology in E. faecalis is that MGEs that are targeted by native CRISPR-Cas systems can be maintained transiently.
We show that maintenance of chromosomal targeting constructs results in the induction of prophages but no induction of canonical SOS response genes, including recA
Our findings reveal a novel strategy exploited by a bacterial pathogen to cope with CRISPR-induced conflicts to more readily accept DNA, and our robust CRISPR editing platform will help simplify genetic modifications in this organism.
We determined that low cas9 expression contributes to this transient nonlethality and used this knowledge to develop a robust CRISPR-assisted genome-editing scheme.
Among the prime causative factors for the spread of antibiotic resistance is horizontal gene transfer (HGT).
since the species possesses highly conjugative plasmids that readily disseminate antibiotic resistance genes and virulence factors in nature.
and CRISPR-associated protein (Cas) genome defense systems.
but at a fitness cost.
Our results suggest that E. faecalis has maximized the potential for DNA acquisition by attenuating its CRISPR machinery, thereby facilitating the acquisition of potentially beneficial MGEs that may otherwise be restricted by genome defense.
CRISPR tolerance protects against self-targeting.
The targeting complex then locates the protospacer (red rectangle; identical in sequence to spacer) on the recipient chromosome and cleaves the target sequence.
Transcriptomic responses to CRISPR-Cas9 self-targeting and LVX treatment.
CRISPR self-targeting induces prophages.
CRISPR-Cas chromosome targeting, which leads to double-stranded DNA breaks, is lethal.
In this study, we show that chromosomal CRISPR targeting in Enterococcus faecalis is transiently nonlethal.
human gastrointestinal tract
due to expanded collections of mobile genetic elements
lack cas genes associated with clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein (CRISPR-Cas) systems
, which act as adaptive immune systems against bacteriophage
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