ESX1 and infection: It achieved nearly wild-type bacterial burdens during zebrafish larval infection (0.82 ± 0.16 fold of wild type vs. 0.29 ± 0.05 fold for Mm−ΔRD1), and this was associated with wild type levels of granuloma formation, an ESX-1–mediated phenotype (Fig. 1 F–H) (3, 11, 12).