Figure 3: In situ detection of reactive nitrogen species. Wild-type zebrafish embryos (Albino; 28 hpf) were injected into the caudal vein with 200 colony-forming units (CFU) of M. marinum Mma20 expressing a pMST3::mCherry vector. Confocal images were taken of a tail region of the developing larva at 3 days after infection (3 dpi), a point at which the M. marinum infection (a) has been established. Embryos were fixed in 4% paraformaldehyde at 3 dpi, and immunohistochemistry was performed, using an antinitrotyrosine antibody that detects tissue nitration (b) [21]. Colocalization (c) between bacteria and extensive tissue nitration can be observed at this time point. Scale bar: 10  m.