查看文章

Phage‐encoded Shiga toxin (Stx) acts as a bacterial defence against the eukaryotic predator Tetrahymena. To function as an effective bacterial anti‐predator defence, Stx must kill a broad spectrum of predators. Consistent with that assertion, we show here that bacterially encoded Stx efficiently kills the bacteriovore Acanthamoeba castellanii in co‐culture. We also show that, in addition to Stx, the phage‐encoded exotoxin, diphtheria toxin (Dtx) expressed by Corynebacterium diphtheriae also can function as part of an anti‐predator strategy; it kills Acanthamoeba in co‐culture. Interestingly, only exotoxins produced by bacteria internalized by the Acanthamoeba predator are cytolethal; the presence of purified Dtx or Stx in culture medium has no effect on predator viability. This finding is consistent with our results indicating that intoxication of Acanthamoeba by these exotoxins does not require a receptor. Thus bacteria …