The plates were then incubated with 50 μL of culture supernatant from each sample for 1 h at room temperature, before being washed five times in

PBS containing 0.1% Tween 20, and then incubated with 50 μL anti-rabbit IgG conjugated PD 332991 to horseradish peroxidase. After a 1-h incubation at room temperature, color was developed using an ELISA POD substrate TMB kit (Nacalai, Japan). Absorbance at 460 nm was detected using an ELISA plate reader. For whole-cell extracts, the bacteria were resuspended in an SDS sampling buffer (2% SDS, 62.5 mM Tris, 10% glycerol; pH 7.5) and boiled for 10 min. We attempted to detect EspB mRNA using the RT-PCR, and total RNA extracts were prepared from the bacteria using an RNA isolation kit (RNeasy Mini kit; Qiagen, Valencia, CA). RNA samples were subjected to RT-PCR using a pair of primers and an RT-PCR kit (SuperScript III One-Step RT-PCR System; Invitrogen, CA). The primer sets (China et al., 1999) used for the RT-PCR were B148 and B151 for type α (E2348/69) and B148 and B150 for type γ (EDL933), and RT-PCR was performed

according to the following protocol: 94 °C for 2 min, followed by 20, 25, or 30 cycles Cabozantinib manufacturer of 94 °C for 20 s, 55 °C for 40 s, and 72 °C for 2 min. The PCR products were analyzed by gel electrophoresis in 2% agarose. An escN mutant of EPEC E2348/69, which displays a defective secretion of type III-secreted proteins, was kindly supplied by Prof. Abe. Cholic acid (CA), deoxycholic acid (DOC), Triton X-100 (TX), and Nonidet P40 (P40) 3-mercaptopyruvate sulfurtransferase were purchased from Nacalai Co. (Tokyo, Japan), and the LB broths supplemented with each detergent were designated CA–LB, DOC–LB, TX–LB, and P40–LB. The results are expressed as the mean ± SD. Differences between two groups were determined using the two-tailed, unpaired Student’s t test. P≤0.05 was considered to be significant. E2348/69 (EPEC) or EDL933 (STEC) was cultured

in LB broth supplemented with either 1% or 0.1% detergent at 37 °C for 12 h, and then we examined bacterial growth and EspB production. The bacteria grew as well in each LB broth supplemented with detergent as in LB broth without detergent. EspB was detected in all of the 0.1% detergent–LB cultures by Western blotting, but its concentration varied in 1% detergent–LB (data not shown). To elucidate the optimal detergent concentrations for EspB secretion, the bacteria were cultured in LB broth with various concentrations of detergents (1.5–0.003%), and the numbers of EspB in the culture supernatants were determined. The results obtained from three separate experiments by Western blotting are shown in Fig. 1. The optimal detergent concentrations for both pathogens were estimated as the percentage value that produced the most EspB in both pathogens, and were determined as 0.1% for CA, TX, and P40, and 0.05% for DOC. To examine the time course of EspB secretion, the culture supernatant was collected at 2, 6, and 10 h (Fig. 2a).