FIG. 1.

Features of Bordetella hur-bhu genetic system and bhuR-lacZ transcriptional fusions. The bhu genes encode a heme utilization system in B. pertussis and B. bronchiseptica (70). The arrows represent the spatial limits and direction of transcription of genes. The open circle represents the predicted σ⁷⁰-dependent hurI promoter, and vertical bars indicate predicted overlapping Fur-binding sites. The solid circle upstream of bhuR indicates the location of sequences similar to ECF σ factor −10 and −35 elements predicted to comprise a HurI-dependent promoter. Transcriptional bhuR-lacZ and hurIR bhuR-lacZ fusions were constructed and maintained on low-copy plasmids pRK41 and pRK42, respectively. Solid bars represent portions of the hur-bhu genetic region, and the open arrow represents the promoterless trp′-′lacZ gene.