FIG 2.

Evaluation of β-lactamase activity. (A) Induction of β-lactamase activity in C. difficile (C. dif) ATCC 43255 and C. difficile 630Δerm by three representative antibiotics. Their activity increases in the presence of NaHCO₃ and is not inhibited by EDTA. (B) Distribution of β-lactamase between the bacterial cells and growth medium. (C) Expression of CDD-1 and CDD-2 enzymes from their own promoters in C. cochlearium ATCC 17787. The right panel shows 5-fold-concentrated cell pellets. (D) Expression of CDD-1 from two functional promoters in C. cochlearium ATCC 17787. (E) Loss of CDD-2 β-lactamase activity in C. difficile 630Δerm knockouts. Activity was measured in 5-fold-concentrated cell pellets. Abbreviations: BC, bacterial culture; NIT, nitrocefin; NA, no antibiotic; AMP, ampicillin; CTR, ceftriaxone; CAZ, ceftazidime; P, pellet; S, supernatant; CP, control pellet of the parental strain; IK, insertional knockout; DK, deletion knockout.