Demonstration and preliminary characterization of a regular array in the cell wall of Clostridium difficile

Abstract The presence of a regular array (RA) was demonstrated on the outer layer of the cell wall in Clostridium difficile GAI0714 by electron microscopy. The RA was composed of squarely arranged subunits with a center-to-center spacing of about 8.2 nm. The outer wall layer carrying the RA was isolated from the wall fragments of early log-phase cells by autolysis. The outer wall layer was composed of two main proteins with apparent M _rs of about 45 000 and 32 000 upon sodiumdodecylsul-fate-polyacrylamide gel electrophoresis (SDS-PAGE). Similar RAs were also present in the cell walls of the other 9 strains of C. difficile . These strains were divided into two groups on the basis of the wall protein composition: one containing M _r 45 000–47 000 and 32 000 proteins and the other containing M _r 42 000 and 38 000 proteins.