FIG 1.

Schematic representation of the K-antigen capsule locus in P. gingivalis strain W83. The region is predicted to encode 17 open reading frames (PG0104 to PG0123). Shown is the 77-bp inverted repeat element (77bpIR) located 206 bp 5′ of the start codon of PG0106 and 477 bp 3′ of the stop codon of PG0104 (topoisomerase III). The element is predicted to form a large (667-bp) stem-loop structure, and the protein (HU-β subunit) encoded by PG0121 near the 3′ end of the locus has been shown to bind the inverted repeat. Also shown is the insertion site and antisense orientation of the erythromycin resistance cassette (Erm^r) used to generate the inverted repeat element mutant strain (Δ77bpIR), as well as the insertion site and orientation of the tetracycline resistance cassette (Tc^r) in the knock-in complementation strain (Δ77bpIR-C). Promoter regions are identified with black arrows, and the dashed line at the bottom of the figure represents the large 19.4-kb operon transcript, PG0104-PG0121, which encodes the 77bpIR element (shown as a stem-loop) near the 5′ end of the transcript.