Escherichia coli strain NG7C was shown to bind iodine-labeled human type IV collagen (Cn). The binding was rapid and saturable. The number of binding sites was estimated to be 1.5 x 10(4) sites/cell and the dissociation constant 85 nM. The binding was inhibited by unlabeled type I, type IV, and type X Cn, gelatin and, at high doses by vitronectin and fibrinogen. Heat treatment of bacteria abolished the binding. A cell sonicate of strain NG7C inhibited the binding. Heat or protease treatment of the sonicate reduced its inhibitory activity by more than 50%. Cell surface extracts of strain NG7C likewise inhibited Cn binding. Cells of E. coli NG7C also bound to type IV Cn immobilized on microtiter plates. The Cn binding appears to be mediated by cell surface protein(s). Type IV Cn binding to E. coli NG7C differed from the earlier reported Cn binding mechanisms to E. coli, i.e., binding of soluble type II Cn, and from binding of immobilized type V Cn by enterobacteria. E. coli strains can thus produce different surface proteins which mediate binding to collagens. Expression of Cn binding by E. coli may enhance colonization of subepithelial tissues.