Protecting from Envelope Stress: Variations on the Phage-Shock-Protein Theme

Area of Science:

• Microbiology
• Molecular Biology
• Bacterial Physiology

Background:

• The phage-shock-protein (Psp) system is crucial for maintaining inner-membrane functions in bacteria under stress.
• This system is well-characterized in Gram-negative bacteria like Escherichia coli, with known regulatory and effector functions.
• Previous studies indicated limited conservation of the Psp system across different bacterial phyla.

Purpose of the Study:

• To investigate the conservation and variation of the Psp system across diverse bacterial phyla.
• To identify conserved components and novel regulatory/effector proteins associated with the Psp system in Firmicutes and Actinobacteria.
• To understand how variations in the Psp system relate to bacterial cell envelope structures and lifestyles.

Main Methods:

• Bioinformatic searches for Psp system components across various bacterial phyla.
• Comparative analysis of PspA orthologs and associated proteins in Firmicutes and Actinobacteria.
• Functional inference based on protein association and known roles in Gram-negative bacteria.

Main Results:

• Searches across phyla confirmed that only PspA is universally conserved within the Psp system.
• In Firmicutes and Actinobacteria, PspA orthologs were found to associate with different regulatory and effector proteins.
• These associated proteins perform functions analogous to those observed in the Psp systems of Gram-negative bacteria.

Conclusions:

• The Psp system's core function is ancient and conserved across prokaryotes, highlighted by PspA conservation.
• Variations in Psp system components across phyla demonstrate significant adaptation to distinct bacterial cell envelopes, lifestyles, and morphogenetic strategies.
• The study reveals the Psp system's adaptability and its importance in diverse bacterial stress responses.