Recipient bacteria (Δbcp-1 Δbcp-2) carrying a transposon insertion or deletion in cepR were outcompeted by donor bacteria producing CDI system-1 (Δbcp-2) to a lesser extent than the parent Δbcp-1 Δbcp-2 recipient strain (Fig. 1A). The gene discussed is GPER1; the disease is clostridium difficile infection.