FIG. 2.
Expression of siiA and secretion of SiiE during culture of S. enterica serovar Typhimurium in various growth media. (A) The reporter strain MvP618 harboring the siiA::luc fusion was grown overnight in LB broth. Various culture media, as indicated, were inoculated with 1/30 volume of the overnight culture, and bacteria were cultured in baffled glass flasks at 37°C with aeration. The culture growth was recorded by measurement of the OD600 (circles). Samples were taken at various time points during culture and processed for quantification of luciferase activity. Means for relative light units (RLU) and standard deviations are shown (bars). (B) WT S. enterica serovar Typhimurium or a SPI4 deletion strain was grown in LB broth, and samples were collected at various time points during culture. The bacterial cells were removed by centrifugation, and the culture supernatants were passed through 0.45-μm filters to remove residual bacteria. An ELISA was used to determine the relative amounts of secreted SiiE, and means and standard deviations of OD450 readings are given for triplicate samples. (C) The WT strain was grown for 14 h in various culture media as indicated (LB, Luria broth; PCN + 7.4, minimal medium with 25 mM Pi, pH 7.4; PCN-7.4, minimal medium with 0.4 mM Pi, pH 7.4; PCN-5.8, minimal medium with 0.4 mM Pi, pH 5.8; M9, minimal medium; DMEM, Dulbecco's modified Eagle medium, cell culture medium), and the secretion of the adhesin SiiE was analyzed by ELISA as described for panel B.