FIG. 1.

Schematic diagrams of M. catarrhalis gene products involved in the truncated denitrification pathway and construction of relevant mutants. (A) The truncated denitrification pathway in M. catarrhalis involves the first three enzymatic steps shown. M. catarrhalis apparently lacks the ability to reduce N₂O to N₂ (indicated by brackets). (B to D) Schematic diagrams of the M. catarrhalis chromosomal locus containing the norB, nsrR, and aniA genes and flanking regions in (B) wild-type O35E strain, (C) the O35E nsrR mutant, and (D) the O35E aniA mutant. The relative positions of the different primers used for PCR are indicated by arrows.