Bacterial capsules: no barrier against Bdellovibrio

Area of Science:

• Microbiology
• Bacteriology
• Cell Biology

Background:

• Escherichia coli (E. coli) possesses a polysaccharide capsule that typically protects against bacteriophages and immune defenses.
• The predatory bacterium Bdellovibrio bacteriovorus (B. bacteriovorus) invades and replicates within the periplasm of Gram-negative bacteria.
• The interaction between bacterial capsules and predatory bacteria like B. bacteriovorus is not well understood.

Purpose of the Study:

• To investigate whether the polysaccharide capsule of E. coli K29 acts as a barrier against invasion by B. bacteriovorus 109J.
• To determine the effect of capsulation on the bdelloplast formation and lysis process by B. bacteriovorus.

Main Methods:

• Culturing of capsulated and non-capsulated E. coli K29 strains.
• Co-culturing of E. coli K29 with B. bacteriovorus 109J.
• Transmission electron microscopy (TEM) to visualize bacterial interactions, capsule integrity, and bdelloplast formation.

Main Results:

• B. bacteriovorus 109J successfully attached to and penetrated both capsulated and non-capsulated E. coli K29 cells.
• Electron microscopy showed B. bacteriovorus penetrating the thick E. coli capsule without significant disruption of the capsular matrix.
• The E. coli capsule remained intact during bdelloplast formation, and prey cell lysis was not affected by the presence of the capsule.

Conclusions:

• The polysaccharide capsule of E. coli does not impede invasion by B. bacteriovorus.
• Unlike its role against phages and immune systems, the E. coli capsule is not a barrier to B. bacteriovorus predation.
• B. bacteriovorus efficiently invades and lyses E. coli regardless of its capsular status.