FIG 4.

S. Paratyphi A grown aerobically to the late logarithmic phase expresses lower levels of SPI-1 genes than S. Typhimurium. (A) Total RNA was harvested from S. Typhimurium SL1344 and three S. Paratyphi A strain (45157, 118239, and 9150) cultures grown aerobically to the late logarithmic phase at 37°C, and extracted RNA was subjected to qRT-PCR. The fold change in the abundance of SPI-1 gene transcripts (normalized to rpoD) in S. Paratyphi A strains relative to their expression in S. Typhimurium is shown. The indicated values present the means and the SEM from three independent RT-PCR experiments from two independent RNA extractions. (B) SDS-PAGE Western blot analysis of bacterial cell lysate from S. Typhimurium SL1344 (STM) and S. Paratyphi A 45157 (SPA) strains grown aerobically to the late logarithmic phase. Protein fractions were probed using anti-HA antibody and anti-DnaK antibody as a control. (C) S. Typhimurium SL1344 and S. Paratyphi A 45157 cultures were grown in LB for 5.5 h and normalized to an OD₆₀₀ of 2.4 to 2.6. Exogenous human cytochrome c (8 mg) was added to the bacterial cultures as a precipitating and loading control. Supernatant (5 ml) cultures were precipitated by TCA, and equal amounts (25 μl) from the precipitated fractions were separated on an SDS-12% polyacrylamide gel and stained with Coomassie G-250.