Iron uptake in Plesiomonas shigelloides: cloning of the genes for the heme-iron uptake system

The iron uptake systems of Plesiomonas shigelloides strains were determined. Siderophore production was not detected by chemical or biological assays, and the strains tested were unable to use enterobactin, aerobactin, or vibriobactin for growth in low-iron media. Both hemin and hemoglobin supported full growth of the bacteria in media lacking other iron sources, but neither transferrin nor lactoferrin served as a source of iron. Hemolysin was detected, and the production of hemolysin was iron repressible. DNA sequences encoding hemolysin production and DNA sequences encoding the ability to use heme or hemoglobin as a sole source of iron were cloned from P. shigelloides and expressed in Escherichia coli. The abilities to use heme and hemoglobin as iron sources were closely linked, and the cloned sequences encoded the ability to transport the porphyrin, as well as iron, into the cells.