TABLE 1.
Bacterial strains used in this study and their relevant virulence properties
| Straina | Description | Invasion of HeLa cells | Type III secretion | Refer- ence |
|---|---|---|---|---|
| 2457T | Wild type | + | + | 12 |
| 2457O | 2457T virF::IS2 | − | − | 34 |
| BS103 | 2457T cured of the virulence plasmid | − | − | 27 |
| BS228 | 2457T ipaB::λplac Mu53 | − | +b | 18 |
| BS232 | 2457T mxi::lacZ | − | − | 18 |
| BS545 | 2457T spa33::aphA3 | − | − | 49 |
| BS547 | 2457T mxiM::aphA3 | − | − | 50 |
| M90T | Wild type | + | + | 47 |
| BS176 | M90T cured of the virulence plasmid | − | − | 48 |
a
All strains are derivatives of S. flexneri 2a except M90T and BS176, which are strains of S. flexneri 5.
b
Insertion in BS228 results in synthesis of a truncated IpaB product and is polar on the downstream ipa genes; i.e., IpaC, IpaD, and IpaA are not synthesized.