Dominance patterns of Aer mutant (Aer*) defects. The tryptone soft agar colony morphology of UU1250 strains carrying both a pMB1-Aer* plasmid and pKG117, a wild-type Aer plasmid, is shown after 17 h of incubation at 30°C. (Left) Aer* only induced. (Right) Aer wild type (WT) only induced. (Middle) Both Aer* and Aer WT induced. The scoring patterns are given in parentheses for the following mutants: L220P (recessive), L256R (dominant, reduced size), N228S (dominant, impaired ring), A223V (dominant, reduced size and impaired ring), and Q263L (dominant, null phenotype). Sal, sodium salicylate. The vector control colonies contain both vector plasmids (pCJ30, pKG116) and no WT Aer plasmid.