Figure 2.

Characterization of BT-derived inhibitory factors on CD toxin production. (a) Heat stability was examined by heating the culture supernatant of BT or Escherichia coli DH5α at 100 °C for 10 min. After CD was cultured in either GAM broth or the conditioned media containing either heated- or unheated-culture supernatant, Toxin A level in the culture was compared by Western blotting with anti-Toxin A antibody. (b) Size fractionation of the culture supernatant of BT by Amicon^® ultrafiltration column. Filtration sizes are indicated above the lanes. “Whole” indicates the unfiltered sample. CD was cultured in the conditioned media prepared with either the filtered or unfiltered BT culture supernatant; Toxin A level in the culture was compared by Western blotting with anti-Toxin A antibody. M, HRP-labeled protein size marker (220 kDa).