Although Vibrio vulnificus is known to be able to utilize ferrioxamine B as an iron source, its outer membrane receptor remains to be determined. In this study, we found that V. vulnificus expressed a new outer membrane protein of 78 kDa when grown in the presence of desferrioxamine B under iron-limiting conditions. The desferrioxamine B-dependent iron uptake was only observed in bacterial cells expressing this protein. Furthermore, non-denaturing polyacrylamide gel electrophoresis followed by autoradiography of the outer membrane preparation containing the 78-kDa protein preincubated with [(55)Fe]ferrioxamine B provided a single radioactive band in which the 78-kDa outer membrane protein was present as the major component. These lines of evidence suggest that the inducible 78-kDa protein may serve as the cell-surface receptor for ferrioxamine B.