Haemolytic activity and cytotoxicity of G. anatis 12656-12 wild-type (wt) and the isogenic gtxA mutant (ΔgtxA). (A) β-haemolysis. The bacteria were streaked on BHI-agar plates with 5% bovine blood and incubated at 37 °C for 18 h. (B) Light microscopy (100 × magnifications) of HD11 cells after 1 h incubation with saline (mock), wt or ΔgtxA. Bacteria were harvested in late exponential phase (OD600 = 1) and added at an m.o.i. of 10. (C) Cytotoxicity quantified with LDH activity. HD11 cells were incubated with bacteria as described in 1B. The averages of three replicate wells are shown, bars represent the S.E.