To further study the link between CFD susceptibility and cell physiology under iron limitation, we constructed a panel of CRISPRi mutants in all 24 putative TBDRs encoded in K56-2, in addition to fur, encoding the iron-responsive Fur transcriptional repressor, and the four tonB paralogues (Supplementary Table 6 and Supplementary Fig. 9). The gene discussed is FURIN; the disease is fleck corneal dystrophy.