FIG 1 .
Role of StxB in Stx2-mediated Tetrahymena killing. (A) Tetrahymena cells were separately cultured in medium with no additions or containing MG1655::933W or MG1655::933WΔB for 6 h at 30°C. The number of live Tetrahymena cells was determined after 6 h as described previously (5). Data are presented as the number of live Tetrahymena cells after incubation relative to the number of live Tetrahymena cells at the start (t = 0) of incubation. Error bars represent standard deviations from three or more independent experiments, with each experiment comprising a minimum of three individual measurements *, P < 0.01 relative to the control. (B) Tetrahymena cells were axenically cultured with 40 ng/ml Stx2 holotoxin or BSA alone or 40 ng/ml Stx2 holotoxin in the presence of 2 µg/ml StxB. The number of live Tetrahymena cells was determined after 6 h. Data are presented as the number of live Tetrahymena cells after incubation relative to the number of live Tetrahymena cells at the start of incubation. Error bars represent standard deviations from three or more independent experiments, with each experiment comprising a minimum of three individual measurements. *, P < 0.01.