Characterization of the Vibrio cholerae heme iron transport system and its role in pathogenesis

Abstract

Vibrio cholerae can utilize hemin or hemoglobin as its sole source of iron. The ability to use these iron sources is independent of production of the siderophore vibriobactin. The V. cholerae heme utilization system can be reconstituted in Escherichia coli 1017 by transformation with two recombinant plasmids, pHUT3 and pHUTlO. These plasmids contain at least two genes required for utilization of heme iron. One of the genes encoded by pHUTIO specifies a 26 kDa inner membrane protein. The second plasmid, pHUT3, encodes a 77 kDa outer membrane protein. Tn5 mutagenesis of the plasmids indicates that loss of either the 77 kDa or the 26 kDa protein leads to loss of ability to use heme as an iron source. The effect of iron on expression of these proteins was determined by analysis of protein levels and measurement of Tn5 lac gene fusions. Expression of the 77 kDa protein, like the siderophore and hemolysin, is negatively regulated by iron. Regulation is mediated by the V. cholerae analog of the E. coli fur gene. V. cholerae mutants defective in heme transport and/or siderophore production were constructed and tested for virulence in the infant mouse model. A mutant defective in both siderophore production and heme transport was unable to cause disease in this model.