Cell surface proteins (biofilm matrix and
cell wall fractions) isolated from S. aureus MR23 biofilms were separated
by one-dimensional (1D) SDS-PAGE. The major protein bands with ap-
parent molecular masses of 60 kDa and 15 kDa were identified by N-ter-
minal amino acid sequence analyses as described previously (20). Top-
down proteomic analysis was also performed to identify proteins that are
degraded by Esp (details are described in the supplemental material)