TABLE 3.
CsrA and Cra influences on S. flexneri virulence in cell culture assays
| Strain | Genotype | % wild type invasiona | Plaque morphology and relative no.b |
|---|---|---|---|
| 2457T | Wild type | 100 | + |
| AGS120 | csrA::Kan | 5 ± 4 | pp, <10% WT |
| AGS120/pQCsrA | csrA::Kan/pQCsrAc | 47 ± 6 | pp, ∼20% WT |
| AGS190 | cra::Kan | 131 ± 13 | pp |
| AGS190/pWCra | cra::Kan/pWCra | 90 | + |
| AGS100 | barA::Kan | 98 ± 9 | + |
| AGS110 | uvrY::Kan | 143 ± 10 | + |
| AGS130 | csrB::Cm | 111 ± 10 | + |
| AGS140 | csrC::Tet | 126 ± 5 | + |
| AGS150 | csrD::Kan | 43 ± 10 | <10% WT |
| 2457T/pQCsrB | pQCsrBc (CsrB overexpression) | 53 | ND |
| 2457T/pQCsrC | pQCsrCc (CsrC overexpression) | 53 | ND |
| AGS220 | pfkA::Kan | 0 | − |
| AGS220/pWPfkA | pfkA::Kan/pWPfkA | 77 ± 10 | + |
Percentage of Henle cells with ≥3 intracellular bacteria. Invasion rates for wild-type (WT) strain 2457T ranged from 70 to 85% in different experiments, and values for the other strains were normalized to the invasion percentage of the wild type within each experiment. At least 300 Henle cells were counted in each experiment, and the values given are averages ± 1 standard deviation of three independent experiments each performed in triplicate. The data shown for complementation of csrA and cra and for csrB and csrC overexpression are averages of two independent experiments performed in triplicate.
+, clear plaques of ∼1.5 mm, number of plaques equivalent to WT (100 to 200 plaques/well); pp, pinpoint turbid plaques with diameter of <0.5 mm; −, no visible plaques; ND, not determined. The relative number of plaques (as a percentage) is based on the number of plaques formed by the WT in the same experiment.
Expression was induced by addition of 200 μM IPTG.