Purified outer membranes of Serpulina hyodysenteriae contain cholesterol

The purified membranes of Serpulina hyodysenteriae was examined to determine whether they contained cholesterol. The study made use of discontinuous sucrose density gradients to isolate outer and inner membranes. Results revealed that the outer and inner membrane fractions contained less than 1% and 2% of the total NADH oxidase activity in the cell lysate. Treatment with different concentrations of digitonin showed that the outer membrane could be selectively be removed at concentrations to about 0.125%.