CBASS limits bacteriophage production while maintaining cell viability in Pseudomonas aeruginosa

Area of Science:

• Microbiology
• Bacteriology
• Virology

Background:

• The cyclic-oligonucleotide-based anti-phage signaling system (CBASS) is a bacterial immune pathway that combats phage infections.
• Membrane-acting CBASS effectors are hypothesized to induce host cell death, but this has not been verified at endogenous expression levels.

Purpose of the Study:

• To investigate the cell viability effects of the CBASS phospholipase effector (CapV) when activated by 3',3'-cGAMP in Pseudomonas aeruginosa.
• To assess the anti-phage efficacy and host fitness costs associated with CapV activation.

Main Methods:

• Activation of the CapV effector using exogenous 3',3'-cGAMP and constitutive signaling via the synthase (CdnA) in Pseudomonas aeruginosa.
• Monitoring of cell growth, viability, and phage production under CBASS activation.
• Analysis of phage transcription, DNA replication, and DNA packaging during infection.

Main Results:

• Constitutive CapV activation by 3',3'-cGAMP signaling resulted in robust cell growth and viability, contrary to expectations of cell death.
• Phage production was abolished, with normal phage transcription and initial DNA replication, but impaired DNA packaging.
• No significant cell fitness cost was observed with constitutive CapV activation, which effectively blocked multiple phages.

Conclusions:

• The CBASS phospholipase effector (CapV) effectively inhibits phage replication in Pseudomonas aeruginosa without inducing host cell death.
• CapV is proposed to disrupt phage capsid assembly at the inner membrane, preventing stable DNA packaging and viral maturation.
• This mechanism allows for potent anti-viral activity while preserving host cell viability, representing a novel anti-phage strategy.