A Bordetella pertussis fepA homologue required for utilization of exogenous ferric enterobactin

The bfeA (Bordetella ferric enterobactin) receptor gene was cloned from a Bordetella pertussis chromosomal library by using a screen in Escherichia coli to detect iron-repressed genes encoding exported proteins translationally fused to the E. coli phoA gene. The bfeA gene encoded a protein with a molecular mass of approximately 80 kDa and about 50% amino acid sequence identity to both the fepA- and pfeA-encoded enterobactin receptors of E. coli and Pseudomonas aeruginosa, respectively. Enterobactin prepared from iron-starved E. coli cultures supported growth of B. pertussis and Bordetella bronchiseptica in the presence of the iron chelator ethylenediamine-di-(o-hydroxyphenylacetic acid) (EDDA). Expression of the bfeA gene was induced by low iron availability, and iron-regulated expression appeared to be dependent upon the presence of the sequence contained within 370 bp upstream of the bfeA structural gene. An internal fragment of the bfeA structural gene and flanking regions were shown by Southern analysis to be highly conserved among Bordetella species. Insertional inactivation of bfeA in both B. pertussis and B. bronchiseptica greatly impaired their ability to grow in the presence of enterobactin and EDDA. These findings suggest that enterobactin produced by other respiratory flora could aid in the colonization of the respiratory tract by Bordetella species.