pili competitively inhibited whole cell binding antibodies specific for the p aeruginosa stain k pak type iv pili rabbit polyclonal antibody and monoclonal antibodies pk99h and pk3b prevented adherence of both viable cells and purified pili to steel as antibodies specific for the c terminal pila receptor binding domain inhibited adherence the role of the piia receptor binding domain in mediating binding to steel surfaces was examined a synthetic peptide of the pak pila epithelial cell receptor binding domain pak 128 144 ox bound directly to steel with a very high affinity the interaction of pili with steel was specifically inhibited by this peptide with an apparent ki of u02dc 0 2 nm and specifically inhibited the binding of viable homologous and heterologous p aeruginosa strains to steel with an apparent ki of u02dc 4 nm therefore the c terminal pila receptor binding domain mediates binding to both biotic and abiotic surfaces although this binding function appears to be optimized for binding to abiotic surfaces rather than for adherence during the infectious process initial colonization of stainless steel is dependent upon type iv pili in p aeruginosa while the involvement of type iv pili in biofilm formation on abiotic surfaces has been well documented o 39 toole and kolter 1998 klausen et al 2003 the molecular basis for that involvement has not been firmly established therefore we investigated the ability of p aeruginosa wild type strains pak pao k122 4 and kb7 which display considerable differences in their pilin sequences to bind to stainless steel fig1 a b p aeruginosa pilins are characterized by a highly conserved n terminal a helix and a semi conserved c terminal disulfide loop region but display minimal sequence similarity through the bulk of.