FIG. 4.

Construction of the hmuR mutant WS1. (A) The P. gingivalis hmuR insertional mutant (WS1) was constructed following insertion of the ermF cassette (with flanking sequences) in the PstI site of hmuR. The direction of transcription is indicated by an arrow, and the PstI restriction site(s) of hmuR and ermF are noted. Also indicated is the map of hmuR region from P. gingivalis A7436. Upstream of the hmuR gene we identified an ORF of 438 bp (hmuY), predicted to encode a 145-aa protein. The promoter region of hmuY contains a putative Fur consensus binding sequence (13 of 19 bases identical to the E. coli Fur box; the Fur box is not drawn to scale). Located downstream of hmuR, an ORF which encodes a putative Mg chelatase (mg che), which was disrupted by a gene encoding a IS10-like element, was identified. (B) Southern blot analysis of chromosomal DNA from P. gingivalis hmuR mutants probed with an hmuR-specific probe (see Table 2). Lanes 1 to 4, genomic DNA from four separate transformants (WS1, WS2, WS4, and WS5); lane 5, genomic DNA from A7436. Introduction of the ermF cassette adds ∼2.0 kb, causing a shift in the hmuR band.