Interbacterial competition triggers stress-induced CRISPR immunity against bacteriophages.

Interbacterial competition with Acinetobacter baumannii triggers CRISPR-Cas activation and spacer acquisition in Pseudomonas aeruginosa.

• Why it matters: Understanding how natural microbial communities influence phage resistance mechanisms is crucial because bacteria often face complex interspecies interactions that can affect their immune responses and evolution.
• What they did: The study co-cultured P. aeruginosa with A. baumannii and measured CRISPR-Cas gene expression and spacer acquisition, finding increased activity only in the presence of A. baumannii, linked to DNA damage and stress signals.
• The result: Interbacterial antagonism acts as an ecological and physiological trigger for CRISPR activation, suggesting that competitive stress enhances bacterial adaptive immunity and the generation of more resistant genotypes.