Fig 3.

TcsR mediates the transcription of toxin genes. (A) Quantification of toxins in parent ATCC 9714 and tcsR mutant strains. Toxin titers in cytoplasmic proteins harvested from parent and tcsR mutant were determined by ELISA, and the signal from the test was recorded as the absorbance at 405 nm. The data shown are means ± standard errors of three replicate samples. Student's t test was used for statistical analysis. *, P < 0.05. (B) Expression of β-glucuronidase in parent ATCC 9714 and tcsR mutant strains carrying plasmids with gusA as the reporter gene fused to the promoters of tcsL, tcsH, tcsR, and tcsE. Strains carrying a promoterless gusA plasmid (pRGL153A) were used as control. Data represent the means ± standard errors of the means (SEM) (n = 3). (C) Comparison of transcript levels of tcsL, tcsH, tcsR, and tcsE in parent and tcsR mutant strains based on QRT-PCR. Data represent the mean fold change in expression ± SEM (n = 3) compared to the parent ATCC 9714 strain. Ten-hour-old bacterial cultures were used in all the experiments presented.