The bacterial spore suspensions were fixed in 2.5% glutaraldehyde
in 0.1MPIPES (pH 7.4) buffer in 1.5ml polypropylene tubes for a minimum of 2 h. The suspensions were centrifuged (5400 g,
2 min) and resuspended in 0.1 M PIPES (pH 7.4) buffer three times.
After the final centrifugation, the buffer was removed to leave a
pellet.