Culturing and Isolating Capsule-Forming Pathogenic Bacterial Strains

Begin with pathogenic bacterial strains cultured on separate agar plates.

Each strain carries different mutations in genes responsible for producing a capsule, a protective polysaccharide layer.

Transfer single colonies from the plates into separate tubes containing a nutrient-rich liquid medium and incubate.

During incubation, the bacteria enter the exponential growth phase and express the capsule-producing genes.

Mutations in these genes result in variations in capsule production, generating non-capsulated, weakly capsulated, and heavily capsulated cells.

Transfer the cultures and centrifuge to pellet the cells.

Non-capsulated and weakly capsulated cells form dense pellets, while heavily capsulated cels,

due to their hydrated capsule layer, form a less dense pellet.

Carefully remove the supernatant to avoid losing the heavily capsulated cells.

Add a buffer, centrifuge again, and discard the supernatant to eliminate the residual medium.

Resuspend the cells in the buffer to stabilize the bacteria without promoting further growth, thereby preserving the capsule structure.

Select a single colony from a stock plate with a sterile loop, and inoculate 10 milliliters of an appropriate broth.

Incubat