Response of <i>B. fragilis</i> to Pi limitation.

<p>(A) Growth curve in DMM supplemented with varying concentrations of KH₂PO₄. <i>B. fragilis</i> strain YCH46 was grown anaerobically in DMM supplemented with 6.6 mM, 0.066 mM, or 0.0066 mM of KH₂PO₄ at 37°C for 20 h. Optical densities of the cultures at 600 nm were measured over time. Data presented are the mean ± standard deviations of three independent cultures. (B) qPCR analysis of BF1575, BF1576, and BF2756. Total RNA was collected at mid-logarithmic phase (indicated by † in panel A). Expression levels of BF1575 (<i>phoR</i> homolog), BF1576 (<i>phoB</i> homolog), and BF2756 (<i>pstC</i> homolog) in wild type <i>B. fragilis</i> strain YCH46 were measured and normalized with transcriptional levels of <i>rpoD</i>. The transcriptional level of each gene under Pi limitation (0.066 mM or 0.0066 mM) is shown relative to that in DMM supplemented with 6.6 mM KH₂PO₄ (Pi-rich media).