Assimilation of metal ions bound to porphyrins or porphyrin-peptides by Vibrio vulnificus, a human pathogen inhabiting estuarine and marine environments

Vibrio vulnificus, a ubiquitous microorganism in aquatic environments, causes serious septicemia to the immunocompromised host. In addition to protoheme, this species can utilize FeTCPP [ferric tetrakis (4-carboxyphenyl) porphine] as an iron source. In the present study, heme c bound covalently to the protein in cytochrome c, as well as the Fe-TCPP complex formed with a nanopeptide with a high affinity, was found to be useful iron sources for V. vulnificus. This bacterium was also revealed to use Zn-TCPP as a single zinc source. However, other metalloporphyrins such as Mn-TCPP and Pt-TCPP delayed the bacterial growth in the broth containing Fe-TCPP, suggesting interference in the iron assimilation. These results indicate that V. vulnificus may acquire metal ions from both free and peptide-bound metalloporphyrins.