Variation in the surface layer proteins of Clostridium difficile

Surface layers (S-layers) form regular crystalline structures on the outerm ost surface of many bacteria. Clostridium difficile possesses such an S-lay er consisting of two protein subunits. Treatment of whole cells of C diffic ile with 5 M guanidine hydrochloride revealed two major proteins of differe nt molecular masses characteristic of the S-layer on SDS-PAGE. In this stud y 25 isolates were investigated. A high degree of variability in the molecu lar mass of the two S-layer proteins was evident. Molecular masses ranged f rom 48 to 56 kDa for the heavier protein and from 37 to 45 kDa for the ligh ter protein. A further protein component of 70 kDa was detectable in all is olates. No crossreaction was seen between the two major proteins from isola tes that produced different S-layer patterns, and most S-layer proteins fro m isolates with the same or similar banding patterns did not cross-react. T he S-layer proteins,when detected by a combination of Coomassie blue staini ng and immunoblotting, are a useful marker for phenotyping. (C) 2001 Federa tion of European Microbiological Societies. Published by Elsevier Science B .V. All rights reserved.