Diagrams of plasmids containing the wlb genetic loci of B. avium (pLAF-av), B. pertussis (pLAF-pe), B. bronchiseptica (pLAF-br) and B. parapertussis (pLAF-pa). Shaded boxes in the B. avium locus indicate proposed genetic structure based upon similarity to other members of the Bordetellae shown. White boxes in the B. avium locus indicate sequenced areas (wlbA, Accession No. AF248033; wlbF, Accession No. AF248035and No. AF248036; wlbG, Accession No. AF248036; wlbL, Accession No. AF248034). Gene organization of the heterologous wlb loci have been redrawn from published work for comparison (Allen et al., 1998). Insertion sites of B. avium mutants are indicated. Lines above wlbA and wlbL genes indicate the location of digoxigenin-labelled PCR probes. Restriction sites are B, BamHI; C, ClaI; R, EcoRI; H, HindIII; Nd, NdeI; N, NotI; X, XbaI.