Exploiting CRISPR-Cas to manipulate Enterococcus faecalis populations

Area of Science:

• Microbiology
• Bacterial Genetics
• CRISPR-Cas Systems

Background:

• CRISPR-Cas systems act as prokaryotic defense mechanisms against horizontal gene transfer.
• Multidrug-resistant (MDR) Enterococcus faecalis typically lack functional CRISPR-Cas systems, possessing only an orphan CRISPR locus (CRISPR2).

Purpose of the Study:

• To investigate the interaction between CRISPR-Cas genome defense and antibiotic selection on E. faecalis populations.
• To explore the potential reactivation of CRISPR2 for genome defense in MDR E. faecalis strains.

Main Methods:

• In vitro cultivation of MDR E. faecalis populations.
• Monitoring of CRISPR target maintenance under varying selection pressures.
• Assessment of CRISPR2 reactivation and its impact on bacterial populations.

Main Results:

• CRISPR2 can be reactivated for genome defense in MDR E. faecalis.
• E. faecalis transiently maintains CRISPR targets even with active CRISPR-Cas systems.
• CRISPR targets are lost over time; selection pressure dictates persistence, while absence of selection leads to loss.

Conclusions:

• CRISPR2 reactivation offers a novel genome defense strategy in MDR E. faecalis.
• The dynamics of CRISPR target maintenance are influenced by selective pressures.
• Exploiting the fitness cost associated with forced CRISPR target maintenance can alter heterogeneous E. faecalis populations.