The role of surface proteins in Vibrio cholerae attachment to chitin particles in vitro was studied. Treatment of V. cholerae O1 ATCC 14034 and ATCC 14035 with pronase E reduced the attachment of bacteria to chitin particles by 57 to 77%. A statistically significant reduction was also observed when the attachment to chitin was evaluated in the presence of homologous Sarkosyl-insoluble membrane proteins (MPs) (67 to 84%), N-acetylglucosamine (GlcNAc) (62%), the sugar that makes up chitin, and wheat germ agglutinin (40 to 56%), a lectin that binds GlcNAc. The soluble oligomers N,N'-diacetylchitobiose or N,N', N"-triacetylchitotriose caused an inhibition of 14 to 23%. Sarkosyl-insoluble MPs able to bind chitin particles were isolated and visualized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis; two of these peptides (molecular sizes, 36 and 53 kDa) specifically bind GlcNAc.