NFS1 and infection: The defense function of IscS-DndBCDE-DndI was further verified by the discovery that the average burst size of phage PT1 decreased from 72.5 ± 3.24 on infection of ΔdndB-I cell to 50.35 ± 1.17 on infection of ΔdndFGH cell (Supplementary Figure S3C and D).