Cellular responses in Bacillus thuringiensis CS33 during bacteriophage BtCS33 infection

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Bacillus thuringiensis (Bt) is a widely used biopesticide.
• Bacteriophage infections cause significant losses in Bt fermentation (50-80% of batches).
• The molecular mechanisms of phage-Bt interactions remain poorly understood.

Purpose of the Study:

• To investigate the physiological and biochemical effects of bacteriophage infection on Bt strain CS33.
• To identify host proteins and pathways affected by phage infection.
• To understand the impact on Bt growth, cell mass, and insecticidal crystal protein (ICPs) yield.

Main Methods:

• Gel-based proteomics approach.
• Analysis of sequential protein changes in phage-infected Bt cells.
• Comparative analysis of infected and uninfected Bt strains.

Main Results:

• Phage infection suppressed Bt host energy metabolism, including the respiration chain and TCA cycle.
• Phage hijacked the host translational machinery for its own synthesis.
• Cell surface proteins (S-layer, flagella) were altered, potentially mediating phage recognition and resistance.
• Significant decreases in Bt growth rate, cell mass, and ICPs yield were observed, linked to suppressed PHB granule utilization.

Conclusions:

• Phage infection disrupts Bt energy metabolism and hijacks host machinery.
• Host cell surface proteins may play a role in phage resistance or superinfection exclusion.
• Phage infection significantly reduces Bt growth and ICPs yield.
• This study provides novel insights into Bt-phage interactions and potential targets for phage control.