4.9. Purification of Peptidoglycan (PG)

Sacculi were isolated from BCC as described [28], with the following modifications. BCC cells (800 mL) were grown to an optical density of 0.6 at 600 nm and harvested by centrifugation at 7500× g for 15 min at 4 °C. The cell pellet was re-suspended in 6 mL of ice-cold sterile dH₂O. The cell suspension was added dropwise to 6 mL boiling 8% sodium dodecyl sulphate (SDS) solution. The solution was boiled for a further 30 min, and the resulting cell suspension pelleted by centrifugation at 130,000× g for 60 min at 25 °C. The pellet was washed repeatedly with dH₂O until the supernatant was free of SDS, as determined by a published assay [29].