Spatial and temporal control of lysis by the lambda holin.

Area of Science:

• Bacteriology
• Virology
• Molecular Biology

Background:

• Bacteriophage lambda infection culminates in bacterial lysis mediated by specific lysis proteins.
• Lysis involves disruption of bacterial envelope layers by holin, endolysin, and spanin proteins.
• Previous observations noted lysis as a sudden, explosive event at a cell pole, but the underlying mechanism was unclear.

Purpose of the Study:

• To investigate the molecular basis of polar lysis in phage lambda infections.
• To determine the role of holin in the morphology and timing of lysis.
• To correlate holin behavior with the site of lytic rupture.

Main Methods:

• Time-lapse fluorescence microscopy was employed to observe phage lambda infection.
• Green fluorescent protein (GFP)-labeled holin was tracked in real-time.
• Oligomerization of holin and its spatial relationship to lysis events were analyzed.

Main Results:

• Holin proteins were observed to form two-dimensional rafts at cell poles approximately 100 seconds before lysis.
• Holin oligomerization sites were spatially correlated with the sites of lytic blowout.
• The holin protein was identified as the primary determinant of polar lysis morphology.

Conclusions:

• Holin's dynamic redistribution and sudden oligomerization at cell poles are key to initiating polar lysis.
• This mechanism likely provides a fitness advantage through all-or-nothing lysis regulation.
• The holin is the critical factor dictating the explosive, polar lysis characteristic of phage lambda infections.