FIG. 4.

Complementation of RelA/SpoT confers an opaque-plaque phenotype on R. rickettsii Iowa. (A) Vero cell monolayers showing plaques formed by the R. rickettsii Iowa clear-plaque variant, the opaque-plaque variant, a clear-plaque variant clone transformed with the parent pMW1650 plasmid, and three representative clonal isolates after transformation of the R. rickettsii Iowa clear-plaque variant with intact relA/spoT showing restoration of the opaque-plaque phenotype. Bar = 5 mm. The insertion site of the transposon for each of the transformants is given in Table 1. (B) LDH release from Vero cells at 3 days postinfection with each of the R. rickettsii Iowa plaque variants and transformants shown above. Error bars represent SEM.