Our data further show that while the low-level of ExoS-induced cytotoxicity (15–20%) that occurs early (within the first 5 h post-infection) is primarily due to the ADPRT domain activity, the GAP domain is a major contributor to ExoS-induced apoptosis at later timepoints (15–20 h) when ExoS-induced cytotoxicity reaches its maximum level. The gene discussed is PARP1; the disease is infection.