Bordetella pertussis, the causative agent of human
whooping cough, or
pertussis, is an obligate human pathogen with diverse high-affinity transport systems for the assimilation of
iron, a
biometal that is essential for growth. Under
iron starvation stress conditions, B.
pertussis produces the
siderophore alcaligin. The
alcaligin siderophore gene cluster, consisting of the alcABCDERS and fauA genes, encodes activities required for
alcaligin biosynthesis, the export of the
siderophore from the cell, the uptake of the ferric
alcaligin complex across the outer membrane, and the transcriptional activation of
alcaligin system genes by an autogenous mechanism involving
alcaligin sensing. The fauA gene encodes a 79-kDa TonB-dependent outer membrane receptor
protein required for the uptake and utilization of ferric
alcaligin as an
iron source. In this study, using
mixed-infection competition experiments in a mouse respiratory model, inactivation of the B.
pertussis ferric
alcaligin receptor
protein was found to have a profound impact on in vivo growth and survival of a fauA mutant compared with a coinfecting wild-type strain. The attenuating effect of fauA inactivation was evident early in the course of the
infection, suggesting that the contribution of ferric
alcaligin transport to the ecological fitness of B.
pertussis may be important for adaptation to
iron-restricted host conditions that exist at the initial stages of
infection.
Alcaligin-mediated
iron acquisition by B.
pertussis may be critical for successful host colonization and establishment of
infection.